PRODUCTION OF FERROMAGNETIC CHROMIUM DIOXIDE

2124812

American ene by Bayer plant central region 8 j is 1 · Μ β LEVERK 1971 patents, trademarks and licenses

GB/HG

Process for producing ferromagnetic chromium dioxide

The present invention relates to a method for producing high-quality ferromagnetic chromium dioxides for magnetic recording support.

Since the work of S. metres. Ariya and staff (ZhurObscheiKhim. 23, 1241 (1953)) is known, that chromium dioxide by decomposition of chromic acid and elevated temperature can be obtained under elevated Bruckmann clean. In the US Patent 2,956,955 the production of chromium dioxide under hydrothermal conditions been described; but only coarse-particled products with coercive forces have been obtained under 100/t)/s. This chromium Bamit layers in a range for use unfavourable dioxides coercive force: the coercive force was too high for soft magnetic materials, hard magnetic materials for too low. Such products are also unsuitable for magnetic recording method, since the coercive forces are preferably 350/0 ℮ / for this scope.

It has not try to, produce chromium dioxide with improved magnetic properties. Ba is the

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size of the individual particles and magnetic properties of Torrn the main problem lies depend, in the chromium dioxide production therein, to change size and appearance of the individual particles and selectively adjusting the individual particles size distribution as closely as possible - should be as little as possible to also aggregated larger secondary particles, hinder the poling in the magnetic field. In the size range of interest for the coercive force increases with decreasing particle size recording magnetic pulse wherein moremore ähnlidher needle shape of the particles.

To control the particle size and thus also of the other properties of paths through decomposition of chromium trioxide produced a series of hydrothermalemGhromdioxid method have become known, the relate essentially to the use of foreign - or own modifiers upon thermal decomposition of chromium trioxide under elevated pressure and temperature. As modifiers designated by these additives of certain substances properties as particle size, remanence, coercive force and Ourietemperatur be changed. A number of modifiers is described in British Patent 859,937 1,006,610 and and in the üs Patentschrift 3,371,043. For changing the particle size particularly suitable compounds of the elements and the elements are self, th, Ru and of Sn, Fe and its compounds during above all to Curie temperature. In addition particle size is decreased by increasing the amount of modifier controlling the particle size of the resulting modifiers chromium dioxide and shifted to higher values so that the coercive force.

For the effectiveness of said modifiers is

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important, how and under what conditions they are used. One way, the modifying ' introducing effective substances, has been described in US Patent 3,371,043. In a first stage, the so-called nucleation, the modifier in relatively large quantity is under hydrothermal conditions DAB low ferromagnetic chromium dioxide incorporated, zweiten' in a pressure stage, the so-called pigment formation, as seed is reacted further with chromic acid. The modifier should be introduced into active form as possible, in order to keep the amount of the modifier usually expensive small ^. Only then possible disturbances caused by the modifier, such as lowering the saturation magnetization be avoided.

As particularly effective modifier and its compounds such as tellurium dioxide tellurium, tellurium trioxide, ortho-tellurium acid, known. In the single-stage reaction of chromic acid and tellurium compounds under elevated pressure and temperature and staff of Kubota j (.

Violent, Ceram. 46 Soc., 550 (1963) discussed the following mechanism: the tellurium compounds with chromic acid to form the compound first CrgTeOg, as seed the chromium dioxide formation and the particle size influences the controls. 4 spontaneously but inadequately controlled nucleation does not lead to this extending products with desired characteristics. In the quoted coercive forces are only given of at most 120/öe/work.

As in US Patent 3,243,260 is performed a coercive force of maximum 390/0 ℮ / can, by reacting chromic acid and tellurium under increased pressure and increased temperature be achieved although acid, but which is

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tellurium required amount (6 f is, based on chromium acid used) extremely high.

It was now a process for the preparation of modified ferromagnetic chromium dioxide mixed phases from tellurium CrOj-metal oxide mixtures and water at elevated temperature and pressure found, wherein in a first stage in the presence modifying chromium trioxide. Host components, water and optionally further guest components, temperatures of 100 attempts to 300 °c and printing 1 io 500 atmospheres and heated in one or more stages of the process the chromium dioxide mixed phase nuclei formed further mixed with chromium trioxide and optionally further components guest at temperatures of 100-to-450 °c and the above-mentioned printing hydrothermally treated, wherein the oxides as guest components, or hydroxides of Li Pluoride, well, C, Rb is, Ce, copper, silver, loading, mg of, of Zn, CD-ROM, of Mn, of Fe, cobalt, nickel, palladium, aluminum, of Ga, into, of Si, of Ti, para, WS, self, volts, is Nb, Ta is, Rl, bilateral, for GE, of Pb, is Ru, bone, infrared, of Pt, of Sn, Zr is, RF, I is, of Mo, W is, of U, th, Tc is, Rl, amounts up to 25 weight percent eat in, preferably from 0.001 to 15 weight percent, based on cr03, are used, characterized in that the tellurium in the rutile - or tri rutile lattice Porm in crystallizing compounds, of the general type AgTeOg (α=of Cr, PU, AI, Ga and/or Mn) in finely divided Porm is used.

Found surprising, that steep chromium dioxide having excellent properties can, if the formation of acting either as seed of Cr₂ ^ Of the hydrothermal reaction with chromic acid or TeO separating nucleated with chromic acid in the first stage of the tellurium, tellurium dioxide, tellurium trioxide or the ortho tellurium acid

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SECONDS

Formation of the connection CrgTeO ^ corresponding amount added (chromium oxide hydrate) or chromium as CrOOHCrgO ^ in finely divided form. It was also found, not only that of Cr ^ ^ OE, but compounds of the type generally AgTeOg (α=of Cr, of Fe, AI, Ga and/or Mn) act as modifiers, wherein the aforesaid elements can partially replace in any amount and in any number also, i.e. their solid solutions that can also be used.

The manufacture according to the invention for chromium dioxide shares at US Patent described in 3,371,043; the modifier is introduced but not yet known effectiveness in a tellurium, modifying the general type depending on producing the modifier can be ApTeOg still. Since compounds of type a₂TeOg (α=of Cr, of Fe, AI, Ga and/or Mn) have a high tellurium content, you must for nucleation in the first stage are used and little for hydrothermal reaction mixture may consist for the most part from chromic acid used in the reaction pressure.

In the tri rutile lattice, a via structure of the rutile grid, crystallizing oxide compounds from the literature known AgTeOg (C. by Bayer, DDR. Dtsch. Keram. G flat. 39, 535 (1962). Prepared according to the known method

Products (heating of chromium oxide (with LiI) - te0 with₂ in an oxidizing atmosphere at 650 - 700 °c) are very coarse -

the scope less well or not suitable for Piece and proposed here. Since the width of the individual needles in the range 200 - 800 useful chromium dioxide preparations / ' P.] is, as precursor for the must

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Nucleation type serving smaller than the width of the ^ AgTeO preparations to be produced is chromium dioxide particles have needles.

The production of suitable finely divided preparations as modifiers, precursors or components of general type AgTeOg happens so advantageously, finely divided oxides or oxide hydroxides or with suitable tellurium compounds that Oxidaquate or tellurium metal are reacted at low temperature or mechanically mixed as possible. So that the reaction can be performed at low temperature e.g., the reactants must present in active form. Chromium oxide hydrate green - e.g. one can trade (a chromium oxide hydroxide) or a Guignetgrün - annealed chromium (III) oxide therefrom at low temperatures -, a - metal salt solutions from precipitations of A (III to) with alkali or ammonia (III) or its metal obtained therefrom by annealing at relatively lower temperatures - oxidaquat represented large surface metal (III to) oxides, particularly small primary particles consist of, with tellurium acid, tellurium trioxide, tellurium dioxide or tellurium metal mixing and the mixture in the temperature range 200 - 600 °c either, preferably 300 - 500 °c, or converting into finely divided or directly with the nucleation stage AgTeOgCrgTeOg insertion.

Preferably the finely divided preparations or the mixtures are obtained on the following AgTeOg type because:

1) to an acidic nitrate solution by dissolving metallic tellurium in the tellurium - e.g. a metal salt is ^ ENT - can be produced, preferably the hit advice or chloride

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Element A (α=of Cr, of Fe, AI, Ga and/or Mn given) and neutralized with ammonia. The gelatinous precipitate is filtered off and washed with little or not only water, so that the filter cake contains Ammonnitmt. The filter cake is dried and decomposed the ammonium nitrate.

For decomposition satisfy, dependent on metal ion a is used, temperatures of 130 - 250 °c. The decomposition of the exothermic reaction takes place under highly Ammonnitrats suddenly. The oxidized tellurium is used here for seohewertigen stage. It remains a loose powder behind, the split of allowed very easy. The X-ray picture only the very broad reflexes of a compound AgTeOg type. The widths reflexes suggest, that the crystallites are very small. The opposite the rutile phase in the X-ray picture of the extremely finely particulate products are additional überetrukturlinienfrirutils DTE is invisible (no order of cations or extremes fineness and bad crystallization). The preparation falls to very loosely and is capable of use in a vibratory mill for further reaction after a Trockennahlung e.g..

2) a metal (III to) - salh solution, preferably nitrates or chlorides, the elements a (a is " of Cr, of Fe, AI, Ga and/or Mn), in respect of formula a Orthotellur8äure₂ ^ TeO is dissolved, is an alkali - or ammonium hydroxide solution in an amount with the stöohiometrisohen cast wholly or partially like or normal, the resulting, very finely divided precipitate is washed salt-free, filtered off and dried at low temperature and optionally in the scent Vakuumtrockensohrank or annealed the light gray to dark green product * X-ray amorphous at a drying temperature of 100 °c with increasing GlUhtemperatur 1st and shows rutile - or tri rutile lattice, wherein the crystallite sizes increase with increasing annealing temperature and with the annealing time. Preferably the at 100 °c dried preparations wherein the nucleation stage are used; this has highlighted look, the precipitation speed also have an influence on the fineness of the 100° g dried preparations wherein exerts, such, precipitated products that are finely divided and thus slow the nucleation stage effective.

3) a metal (III to) - salt solution, preferably nitrates or chlorides, the elements a (alpha=of Cr, of Fe, AI, Ga and/or Mn) is precipitated with a solution of alkali or ammonium hydroxide - TeOg, whose amount is for precipitation of metal salts (III to) - sized, quickly. The failed, very finely divided precipitate is washed salt-free, filtered off, dried in a vacuum drying oven or optionally annealed in air and air at low to medium temperature. By this annealing and oxidizing the preparation from the X-ray amorphous state into a finely divided rutile converts - or tri rutile lattice. With increasing temperature and wherein the air oxidation annealing time X-ray crystallites are greater. Preferred are the X-ray amorphous preparations used for nucleation, particularly finely divided Ghromdioxid mixed phase because they provide.

4) in the presence of water in a precursor reaction can CrgTeOg=GrgTeOg from chromic acid and tellurium CrOj + th under hydrothermal conditions are produced according to the formula 2 in a pressure vessel at temperatures of 100 - 350 °c. With increasing temperature the crystallite size of the X-ray representation in the rutile - or tri rutile lattice crystallizing preparation is increasing. Here too is

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a is

not sure, OH is an order of the cations for tri rutile structure has not taken place, or OH it can be detected because of the bad design of the crystal lattice or not small particle size. This method is the result of using cheap raw materials technically CrgTeOg production, because of their particular effectiveness and the particularly good properties of chromium dioxide mixed phase pigments with were of particular importance mountains.

5) it was also found, not only that the X-ray " - type of tri rutile lattice or rutile crystalline compounds, but also the X-ray amorphous or vacuum oven wherein the nucleation stage are particularly effective 120°g dry products. The precipitates of compounds of general type AgTeOg instead of precipitations

(A is " of Cr, of Fe, al-, Ca and/or Mn) physical mixtures of very finely divided (ΟΗ) can therefore ΑΟ, Α (ΟΗ) 3 te * 0₂ in the ratio of the formula AgTeOg for chromium - or and Te - ^ - ^ TeO a20 compounds and finely divided, HgTeOg, dioxide nucleation are used in the two-stage process for recovering hydrothermal chromium dioxide. It is particularly important here, the Α (ΟΗ) 3 -, - (ΟΗ) and a ΑΟ₂ 03^< * Compound in finely divided and to use particularly reactive superiority, what can be done in known manner by suitable preparation of the compounds, e.g. by rapid cases from concentrated solutions in the cold, by gentle and mild drying and heating at low temperature. The saürstoffaufnähme and training of the 1st stage of the process takes place AgTeOg phase here; here the finely divided compound acts simultaneously as modifier.

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In the implementation of the method they do it one way, or with finely divided chromium trioxide in that fine igea - rutile.

Tri rutile lattice crystallizing compounds, or their X-ray amorphous precursors or their finely divided components from general type AgTeOg (α=CFR, sketch, AI, Ga and/or Mn) and optionally further components with the addition of small amounts of water is mixed guest. This mixture is in a reaction vessel afloat in the autoclave with the provision of a inert gas - ewe inert material and/or oxygen gas or without approximately 1/2 hours to 4 hours excess pressure, preferably in 80 minutes, to temperatures of 100 attempts to 300 °c heated and about 1 To is 10 hours at constant temperature and pressure conditions - held.

After cooling the reaction well pulverized black, ohromatfrei washed with water, filtered and dried under controlled conditions at 120 °c and the magnetic values sohonenden. The yield is in this first stage, the seed stage, 90 - 95 % the theory. The formed Ghromdioxid mixed phase nuclei are then mixed again with chromium trioxide and water, can be added optionally gätkoaponenten again, excess water in the autoclave, as stated above, under Inertgasund/or oxygen - or without Freadgasdruok set, temperatures of 100-to-450 °0 heated and in turn about 1 To is 10 hours at constant pressure and constant temperature leaving. The reprocessing of the 2, stage, the Figmentbildung, takes place as with the 1st stage_; the nucleation, the yield of 95 - 99% of the calculated amount is Figment.

The thus produced on the described chromium dioxide mixed phase pigments have partly very high values for the

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Remamenz coercive forces and on. The germs and pigments of the chromium dioxide Miachphasen consist of acicular particles in a size range of uniform endosperm and size.

0.1 to 2/jm/needle/needle width/length and 0.01 - 0.2 urn.

The excellent magnetic properties and low dimensions of the individual particles according to the method described make particularly suited for recording and reproducing magnetic pulse recovered product - on magnetic tapes, magnetic disks or Magnettroxmneln.

The process of the invention is subsequently explained in more detail by way of example:

a is) precursor

151 g of acid are dissolved in 400 ml distilled HgO tellurium.

120 g of finely divided chromium oxide hydrate green into the solution with stirring (100 g of CrgO ^ be entered accordingly).

As long as water is evaporated with stirring, to a viscous suspension is produced. It is removed in a vacuum oven at 40 °c in the oven and then in air at 110 °c the residual water. The preparation is annealed at 400 °c in 1 hour and shows only the rutile or tri rutile lattice of Cr - X-ray₂ Te0g reflexes of less crystallite size allocated.

b is) nucleation

112.0 the precursor 1 alpha) g with 833 g of CrOj and 14 ml is H₂ 0 good

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this mixture into a Pyrex glass vessel in the autoclave and mixing over 8 hours HgO 280 280 °c holding pressure and hot atom..

Magn. data: brr/Y is. cnr /~=213/g.g.' tM is. 7 * 1

^{R is} THE HC :. =²²¹TO £DEGREES^s J IS

d) pigment formation

833 CrOj + 1 b is 5:6 g of seed grams) + 112 ml is H ^ is O good mixing, filling this mixture into a Pyrex glass vessel and holding 8 hours in the autoclave at 300 and 350 °c ^ I is an O atom pressure.

Magn. data: br/y=469/g.g cnry - 1 * 5 *.

I IS_{The HC} =411 föj

a is) precursor

150 g of metallic tellurium be resolved; in a mixture of concentrated nitric acid and 840 ml HgO 1500 ml

the somewhat cooled solution is filtered and cooled to room temperature. Tellurium nitrate solution is thus obtained with a solution of 940 g of 0 (0 Ν ^) ^. 9 γ In the 1200 ml HgOHgO and neutralized with concentrated ammonia combines with vigorous stirring to pH 6.5 solution in 2 minutes 2700 ml half. After neutralization the volume of the suspension is brought onto 8 1 and the precipitate extracted. The washed filter cake is not i5ö⁰ air dried under normal pressure in a drying oven.

24 hours after a short time passes through the exothermic decomposition of ammonium nitrate starting suddenly permanent

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Response to, the heated product on the 300 - 400 °c.

According 4 hours a second further, less strongly exothermic reaction observed distinct; thereafter the product still remains 6 hours in a drying cabinet. 380 g of a very soft obtained, brown black powder, whose X-ray lines have very broad reflections a rutile structure; the d value for the (110) reflection is 3.20 to - j is? and is in good accordance with the aforesaid of determined by Bayer (DDR. Dtsch. Keram. G flat. 39, 535 (1962)) for Cr₂ Specified value of $3t21 TeOg / /. The widening at the reflection from the lines (110) radiographically certain mean crystallite size is 55 [%] and the specific upper -

- is O

24/m/g/BET surface. The product is ground in a vibratory mill with steatite balls dry.

b is) nucleation

49_{f is} 3 g of the precursor 2a) mixing with 60 ml and 465 g of this mixture in a well and holding ^ crogene HgO Pyrex glass vessel in the autoclave 8 hours at 170 atmospheres pressure and on HgO 300 °c.

Magn. data: brrrT =341/&. g of "¹ ^ / centimeters.

I IS_H0 - 375 /' / ond

d) pigment formation

837^2 + 88 g of seed crogene grams of b) + 70 ml HgO well this mixture mixing, filling into a Pyrex glass vessel and holding 8 hours in the autoclave at 290 and GB 300°0 HgO excess pressure.

Magn. data: brr/j is 475/g.g>="¹ ^ / centimeters.

I IS_{The HC} 427 / ΰ β=J IS

GB

a is) precursor

2000 ml of a molar solution of Cr (Nos ^) ^ - 1.000 + ^ ^ - 2000 ml of a molar solution combining TeO 0.500 hours, at room temperature in a casting with a molar is NH OH solution adding 4000 ml 1.500 ^, intensive stirring, precipitate washing with distilled HgO, filtering and 120 °c to air dry. The first X-ray amorphous light gray precipitate of

para

40 - 80 m/g of specific surface can be transformed by annealing in air in the rutile or tri rutile lattice of - GrgTeOg (87, is O $>CrgTeOg).

b is) nucleation

1190 ^ + 120 g of 3 a is as precursor CrgTeOg crogene grams) + 20 ml HgO mixing well, filling and 8 hours in the autoclave at 200 - 250 atmospheres in a EdelatahlgefäöHgO keep pressure at 280° g.

Magn. data: br/p=292/g.g~¹ ^ / centimeters.

^{X IS} Hc=310/0ej

d) pigment formation

1190 80.0 g of 3 + CrOj g of seed and b) + 160 ml HgO well over 350 °c at 270 and HgO mixing, into a stainless steel vessel filling and 8 hours in the autoclave 300 GB - holding pressure.

Magn. data:&~grams/br/p=506.¹ to CMV.

^{X IS} The HC⁼⁴⁴⁴

a is) precursor

2106 ml of a molar solution of Cr (Nos ^) ^ - 2000 ml + 0.9489 0.500 HgTeO ^ - combining a molar solution, at room temperature in 50 minutes with 2000 ml a 5.000 ^ the NH OH solution under stirring cases molar, precipitate with distilled waters' washing, filtration and drying in air at 120 °c.

The first dark green precipitate of röhtgenämorphe_{A IS}

2 im 157 m/g of specific surface area by air into the rutile or moremore irirutilgitter of annealing can - be CrgTeOyübergeführt' (70.6 % ^ ^ Carbon TeO) -

b is) nucleation

595 g of OrOy + 96 g of 70.6# CrgTeOg containing precursor

4 a is) + 10 ml HgO mixing well, filling into a Pyrexglasgefaß 8 hours in an autoclave at 280 °c and 300 GB and holding pressure.

Magn. data: brrrT 220/gr.g="¹ ^ / centimeters.

I is_FR =²⁴⁶ 4 to 7 4 ό℮

d) Pigmentbildupg

833 g of 56.0 g of seed 4 b is ^ crogene +) + 112 ml HgO good mixing, filling into a Pyrex glass vessel and holding 8 hours at 330 °c 300 atmospheres pressure in the autoclave and above water. ~•.

Magn. data: br/p=461 / ΐ. g of "¹ ^ / centimeters.

I IS_{The HC} =451 To £1.0E]

From

a is) precursor

a 1.054 1897.5 ml (NOj) ^ - 2000 ml of a molar solution of Cr + 0.500 molar HgTeOg type Iösung combining, at room temperature in a cast with 1400 ml a 3.000 molar is NH OH Iösung (70# the calculated amount) enable ^, 15 minutes stirring, then with 600 ml a 3.000 molar is NH ^ OHlöBung (30 la the calculated amount) cases, precipitate washing with distilled water, filtering and drying at 120 °c in air.

The first dark green precipitate of 82 m X-ray amorphous²/ g of specific surface area (by tempering air into the rutile - or tri rutile lattice of the can are released CrgTeOg 82.3 %CrgTeOg).

b is) nucleation

595 g of CrOj + 96 g of 82.3 $of Cr₂ 5 precursor containing TeOg alpha) + 10 ml HgO good mixing, filling into a Pyrex glass vessel and holding 8 hours in the autoclave at 280 °c and 300 atmospheres pressure.

Magn. data: brrjf 211/g.g="¹ ^ / centimeters.

I is_H0 =221 Zöey

d) pigment formation

833 g of 56.0 g of seed CrOj + 5b) + 112 ml is H₂ 0 good mixing, into a Pyrex glass vessel filling and 8 hours at 330 °c and 300 atmospheres pressure in " autoclave keep them afloat.

Magn. data: br/p=485/g.g " ca * y - - 1 * 5

I IS_FR =439 &"]

a is) Precursor

2000 ml of a molar solution of PEG (such ^) ^ - 0.500 0.500 molar HgTeOg solution were mixed and 2000 ml and a 25 °c with vigorous stirring 2000 ml a 3.000 molar of Nb ^ OH solution in a cast added. The precipitate is washed, filtered and air dried at 120°0 "

The first product of about 150 NO/g of specific Oberfl&rönfcgenamorpheohe by annealing in air in the rutile or can - released the PegTeOg moremore frirutilgitter (83.7 be PegleOg).

b is) nucleation

100.0 g of 6 a is as precursor PegTeOgCrOj grams +) + 20 ml HgO 1190 good mixing, a Edelstahlgefäö 8 hours in an autoclave at 280 °c HgO In filling and holding at 200 - 230 GB pressure.

Magn. data: brr/j is "/'h.m ≈ 150'"¹ ^ / centimeters.

I IS_{The HC} 7 - 454/0 ℮

d) pigment formation

1190 80.0 g of seed 6b CrOj grams +) + 160 ml Figo was good mixing, filling into a stainless steel vessel and 8 hours in HgO

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Holding at 350 °c and 270 - 300 atmospheres pressure autoclave,

Magn. data: brr /*=486/g.g j is "¹ cms.⁵/

I IS_Equivalents =431/0 ej

a is) precursor

2000 ml - 2000 ml solution and a 1.000 molar MnSO ^ a 0.500 HgTeOg solution are combined and the mixture at 25 °c molar with stirring in a cast with 2000 ml 2.000 molar is NH OH solution with vigorous stirring and ^ vereetzt initiated much fragrance. The precipitate is washed, filtered off and dried at 120 °c in air.

The X-ray amorphous zunäohst " product of about 60 meters/g of specific surface area by annealing at the ^ air into the rutile - or tri rutile lattice can MngTeOg of converted (96.4 ≠MngTeOg).

b is) nucleation

1190 100.0 g of 7 a is + ^ QrO grams MngTeQg as precursor) + 20 ml HgO good mixing, into a stainless steel vessel filling and 8 hours in an autoclave at 280 °c HgO and 200-to-230 GB pressure maintained. .

Magn. data: brr=^>196 fgfg.g cms.

Ih₀ =240 £0e7

d) PigmentbiIdung

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80.0 + CrOj•1190 g of seed FROM 1 · b is) + 160 ml Η,, 0 good mixing, into klaven 300 °c at 270 - 300 atmospheres and holding pressure. a stainless steel vessel filling and 8 hours HgO car -

Magn. data: br/f=453/g.g "/ cnr.

I IS_FR =375 Bone /]

a is) precursor

a 0.500 molar a1 2000 ml₂ (S0 ^) ^ - 2000 ml solution and a 0.500 HgTeOg solution and the mixture at 25 °c molar are combined with vigorous stirring into a cast with precipitate is washed, filtered off and at 120 °c for GE - 2000 ml 3|000 a molar is NH OH solution ^. The

dried. The product of about 100 m/g of specific surface area X-ray amorphous first by annealing in air can be converted to the rutile - or tri rutile lattice of the AlgTeOg 77.3 ( # AlgTeOg).

b is) nucleation

1190 100.0 g of 8 as precursor AlgTeOgCrOj grams + b) + 20 ml is H₂ 0 good mixing, into a stainless steel vessel filling and 8 hours is H₂ 0 in the autoclave at 280 °c and 200-to-230 GB pressure maintained.

Magn. data: br/p=131/g.g * cmy - - 1 * 5

I IS_{The HC} =196/0 ℮ /

d) pigment formation

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1190 80.0 g of seed 8 b is + ^ crogene grams) + θ ΐ Η ml of 6,, 0 good mixing, filling into a stainless steel vessel and 8 hours in an autoclave at 270 - 300 atmospheres pressure and keep HgO 300 °c.

Magn. data: br/p=467/g.g "¹ ^7 centimeters.

^{T IS} Undec =⁴⁵⁴

a is) precursor

1.000 mol. Te0₂ into 2000 ml 3.000 molar NaOH is added at 20 - 25 °c in a cast to be resolved and 2000 ml 1.000 molar of Cr (NOj ^ - solution. The precipitate is washed, filtered and dried at 80 °c in a vacuum. The first product of about 140 m/g of specific surface area X-ray amorphous or by annealing at the fragrance in the rutile - can.

Tri rutile lattice of the converted CrgTeOg (83.2% of Cr are₂TeOg)

b is) nucleation

952 128.0 g of 9 as precursor CrgTeOgCrOj grams + b) + 16 ml HgO good mixing, into a Pyrex glass vessel filling and 8 hours water in an autoclave at 280 °c and 200-to-230 GB pressure maintained.

-1 5

Magn. data: Brr/para * 265 grams/&. " omy

I IS_H0 =328 / Cöj

d) pigment formation

952 64.0 g of seed ^ crogene + 9 6) + 128 ml HgO g of well-mixing, into a Dyrexglasgefäß filling and 8 hours is H₂ 0 in the autoclave at 350 °c and 270 - 300 atmospheres pressure maintained.

Magn. data: brr=^ ^=488>h.m cnry.

I IS_{The HC} - + 2⁸B IS " I IS

10 Beiapiel

a is) precursor

1000 ml 1.000 molar of Cr (NOj) ^ - solution and 1000 ml 1.000 molar Al (tfOj) are combined and the mixture at 20 - 25 °c in a J solution cast into 2000 ml of NaOH 3.000 1.000 mol TeOg with a solution of a molar precipitated; the Niedersohlag is washed, filtered and dried under vacuum at 80 °c. The first 220 m/g of specific surface area of about X-ray amorphous product by annealing in air can be converted into the rutile - or tri rutile lattice of the CrAlTeOg (CrAlTeOg 84.4%).

b is) nucleation

952 g of CrOj + 10 a is GrAlTeOgals 118.3 g of precursor) + 16 ml HgO good mixing, into a filling and 8 hours in an autoclave at 280 °c HgOPyrexglaagefäß and 200-to-230 GB pressure maintained.

Magn. data: br/f=164/g.g~¹ ^ / centimeters.

I IS_Undec " 257 [Öj

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d) pigment formation

952 g of 64.0 g of seed 10 b is CrOj +) + 128 ml HgO mixing well, into a Pyrex glass vessel filling and 8 hours in an autoclave at 350 °c and 270 - 300 atmospheres pressure holding HgO.

Magn. data: brr ^ p=477/g, g of "¹ to CMV.

I_{the U}o=425 knocking

Example 11

a is) precursor

1600.2 ^ are placed in a stainless steel vessel and 500 ml added crogene grams and adjusted by cooling to a temperature of 5 - 10 °c HgO. With stirring slowly added and the mixture heated 1020.9 g of tellurium powder are in a pressure vessel and 4 hours at 175° g on carrion. The black/one-piece of Cr₂ After cooling te0g product is powdered and 120 °c in air dried. By annealing at the scent of rutile - or tri rutile lattice can be of very finely divided GrgTeOg crystallizing in coarser-part come to X-ray crystallite sizes (97.6 % 'GrgTeOg) (specific surface area of OA. 30 metres ^ / grams).

b is) nucleation

952 g of 64.0 g of precursor 11 a is CrgTeOgCrOj + as) + 16 ml HgO good mixing, into a Pyrex glass vessel filling and 8 hours in an autoclave at 280° g h2o and 200-to-230 GB pressure maintained.

The de a is 13,70622 - - -

Magn. data: brr/para

I IS

The HC

=sec/209 'h.m' ^ centimeters.³/

346/0 ℮=7

d) pigment formation

952 g of 64.0 g of seed 11 b is CrOj +) + 128 ml HgO good mixing, into a Pyrex glass vessel filling and 8 hours in an autoclave at 350 °c and 270 - 300 atmospheres pressure holding HgO.

latenMagn.: brr=488/g.g>^~/ cnr.

I IS_{The HC} 7=460/0 ℮

Example 12

a is) precursor

The precursor according to example 11 a is) is then modified, that

the temperature is held at 175° at 225 °c instead.

para

(Specific surface area about 50 m/g of)

b is) nucleation

952 g of CrOj + g is C^12 a is 64.0 TeOg as precursor) + 16 ml HgO good mixing, into a Pyrex glass vessel filling and 8 hours in an autoclave at 280 °c HgO and 200-to-230 GB pressure maintained.

Magn. data: br/p=277/g * g "¹ cms.

^{I IS} The HC^{s 317}

d) pigment formation

64.0 g of seed 12 b is + 952 g of mixing CrOj) + 128 ml HgO well, wherein Ln is a Pyrex glass vessel filling and 8 hours HgO

Ie A is 13,706 - 23 -

350 °c and holding 270 - 300 atmospheres pressure.

Magn. data: brr=481>/j is for CW.?J IS

^{X IS} The HC=⁴⁷⁴

Example 13

a is) precursor

The precursor according to example 11 a is) is then modified, held at 275 °c rather than that the temperature 175 °c (about 85 m/g of specific surface)

b is) nucleation

952 CrD ^ + 64.0 g of CrgTeOg g of precursor. 13 a is) + 16 ml HgO good mixing, a Pyrex glass vessel filling and 8 hours in _inHgO autoclave at 280 °c and 200-to-230 GB pressure maintained.

Magn. data: brr/>j is 124=^ h.m^-1 ^ / centimeters.

I IS_FR =319 M IS

d) pigment formation

952 CrOj 64.0 g of seed 13 b is +) + 128 ml HgO g of well-mixing, autoclave at 350 °c and 270 - 300 atmospheres pressure maintained. in a Pyrex glass vessel filling and 8 hours is H₂ 0 in

Magn. data: brr ^ p=47⁸ZOvg "¹ ^ / centimeters.

!yY_{c is} =458 jtöj

Ie A is 13,706 24 -

Example 14

a is) precursor

into a stainless steel vessel 600 ml HgO filling, with stirring 1200.15 CrOj g of insertion, to approximately 10 °c slowly with stirring 765.65 g of tellurium and adjusting powder and the mixture in a pressure vessel over this temperature is H hot züetzen₂ 0 4 hours at 250 °c holding. Work-up as in example 10 a is) (specific surface area about 180 m²/ grams).

b is) nucleation

952 128.0 g of precursor 14 a is CrgTeOgCrOj grams + as) + 16 ml HgO good mixing, into a Pyrex glass vessel filling and 8 hours in an autoclave at 280 °c HgO and 200-to-230 GB pressure maintained.

Mägn. Data: br/p=132/g.g *'¹ ^ / centimeters.

fR =²⁷⁵

d) pigment formation

952 CrOj 64.0 g of seed 14 b is +) + 128 ml HgO g of well-mixing, filling into a Pyrex glass vessel and holding 8 hours in the autoclave at 270 - 300 and 350 °c HgODruok atmospheres.

Magn. data: brr=//&481. g of "¹ ^ / centimeters.

ha of =⁴⁹⁰№

Example 15

a is) precursor see example 12a)

b is) nucleation

952 g of CrOj + χ grams of Cr₂ 12 a is TeOg is Ala precursor) + 16 ml HgO good mixing, into a Pyrex glass vessel filling and 8 hours in the autoclave is H₂ 0 at 280 °c and 200-to-230 GB pressure maintained. In response to the magnetic data obtained following CrgTeOg doping:

d) pigment formation

952 cr0 grams₅ 40.0 g of seed 15 b + 1 - 15 b is 6) + 128 ml HgO good mixing, into a Pyrex glass vessel filling and 8 hours in the autoclave is H₂ 0 at 350 °c and 270 of to 300 atmospheres pressure maintained. In particular the following magnetic data are obtained:

Example 16

a is) precursor according to example 12a)

b is) nucleation

952 g of 48.0 g of precursor 12 a is CrOj +) + 16 ml is H₂ 0 good mixing, into a Pyrex glass vessel filling and 8 hours in the autoclave at 280 °c over 1^0 and 200-to-230 GB pressure maintained.

Magn. data: br/p=232/g.g cnry.

^{I IS} The HC=²⁹⁶

d) pigment formation

952 g of CrOj + X g of seed 16b) + 128 ml HgO good mixing, filling into a Pyrex glass vessel and 8 hours in the autoclave at 350 °c in the 270 - 300 atmospheres pressure. and holding HgO individual magnetic data obtained the following:

Example 17

a is) 14 a is precursor as example)

b is) according to example 14 b is nucleation)

ie A is 13,706 27 -

d) pigment formation

952 g of 64.0 g of seed 14 b is CrOj +) + X g of ' ^ comprises FeOOH + 128 ml Ε ^ 0 good mixing, into a 8 hours in the autoclave at 350 °c and HgO pyrexglägefäß filling and over 270 of to 300 atmospheres pressure maintained. It the following magnetic data as a function of the added TF FeOOH amount obtained in.:

Example 18

a is) precursor according to example 12 a is)

b is) according to example 2 b is nucleation 15)

d) pigment formation

952 g of 48.0 g of seed 15 b is 2 + CrOj) + 128 ml HgO mixing well, filling into a 8 hours in the autoclave at X and 270 °c h2o pyrexglägefäß and holding pressure on - 300 atmospheres. In response to the temperature following magnetic data are obtained:

Ie A is 13,706 28 -

Example 19

a is) precursor according to example 12a)

b is) nucleation

952 g of 48.0 g of chromium + CrOj₂ According to example 12 a is TeOg) + 16 ml HgO mixing well, filling into a Pyrex glass vessel and 8 hours in the autoclave at X on HgO^para 0 gB 200 - 230 and holding pressure. Following magnetic data obtained to £s:

d) pigment formation

952 cr0 grams₃ 64.0 g of seed 19 b is 1 - 19 b is 4 +) + 128 ml HgO well over 350 °c at 270 and HgO mixing, into a Pyrex glass vessel filling and 8 hours in the autoclave 300 GB - holding pressure.

It listed in the table are obtained the magnetic data:

Example 20

a is) precursor

200 ml HgO give a stainless steel container In, adding with stirring 200 g of OrOj 101.9 g of AlgO + ^ (200 m is ^ / g of spez. surface) + 233.2 g of tellurium (75.3 Τ℮ 0 ^) acid, 5 - 1ö °c on adjusting, adding slowly with stirring the mixture powder and 4 g of tellurium 127.6 hours at 250 °c on a pressure vessel holding In HgO. The product is dried at 120°ö CrAlTeOg and shows a rutile or tri rutile lattice of very small crystallites - X-ray. (96.0 56 CrAlTeOg);

(SPEC. Surface about 195 m²/ grams)

b is) nucleation

952 + 59.1 g of precursor 20 a is CrAlTeOgCrOj g of mixing as) + 16 ml h2o well, filling into a Pyrex glass vessel and 8 hours in the autoclave at 280 °c to book 200 atmospheres pressure and keep HgO 230.

Magn. data: brrmembrane consists of =98/g.g^-1 ^ / centimeters.

^{I IS} Hc=282 ()// ℮

Ie A is 1 3,706 - 30 -

d) pigment formation

952 g of crogene_{X is} 64.0 g of seed 20 b is +) + 128 ml HgO good mixing, filling into a PyrexgiHU 8 hours in the autoclave at 350 °c and holding excess HgO and 270 - 300 atmospheres pressure.

Magn. data: br/p=486/g.g, cm7

I IS_Equivalents =471/0 ℮ /

Example 21

a is) precursor

136.08 g of finely divided of Cr (is OH) J Pällung (68.2 of Cr₂ 0j) and 97.93 g of finely divided ie0₂ (99.5# te0₂ ) are in the ratio of the compound of Cr₂ ^ Te0 very intensively mixed.

b is) nucleation

1190 g of CrOj + entire mixture of the precursor 21 a is) + 20 ml is H₂ 0 good mixing, filling into a stainless steel vessel and holding 8 hours in the autoclave at 280 °c and 200 - 230 GB HgO on pressure.

Magn. data: br/p=335/g.g "¹ ^ / centimeters.

I IS_H0 =385 To £0eJ

d) pigment formation

1190 80.0 g of seed 21 b is CrOj grams +) + 160 ml HgO good mixing, filling into a stainless steel vessel and 8 hours in the autoclave is H₂ is O at 300 °c and 270 - 300 atmospheres pressure maintained.

Ie A is 13,706 31 -

OatenMagn.: brr=473/g.g>/j is^-1 cms.³/

I IS_{THE HC} 424/0 ℮=7

Example 22

a is) precursor

113.04 g of finely divided powder of CrO (is OH) - (82.1 %CrgOj) and 97.93 g of finely divided te0₂ (99.5# te0₂ ) in the ratio of the compound of Cr₂TeOg intensive mixing.

b is) nucleation

1190 g of + 22 a is CrOj entire precursor) + 20 ml HgO mixing well, filling into a stainless steel vessel and 8 hours at 280 °c in the autoclave over hours and 200 - 230 Bruckmann GB₂ 0 holding.

Magn. data: br/p=299/g.g "¹ ^ / centimeters.

^{I IS} The HC⁼³⁸⁷

d) pigment formation

1190 80.0 g of seed 22 b is CrOj grams +) + 160 ml is H₂ 0 well over 300 °c at 270 and HgO mixing, into a stainless steel vessel filling and 8 hours in the autoclave 300 GB - holding pressure.

Z IS - 1

Magn. data: brr=474/g.g>^ "/ cnr.

I IS_{The HC} =409 föj

Example 23

a is) precursor

55.68 g of finely divided of Cr₂ 58.46 g of finely divided te0 0j and₂ in The de a is 13,706 - 32 -

Ratio of the compound ^ ^ Channel FEQ CFR mixing.

b is) nucleation

1190 g of ^ + 23 a is crogene entire precursor) + 20 ml is H₂ 0 good mixing, into a stainless steel vessel filling and 8 hours in the autoclave is II to₂ 0 280 °c at 200 - 230 and GB pressure maintained.

Magn. data: br/p=270 / üü.g " ^ ^ / centimeters.

I is_{The HC} =341 knocking

d) pigment formation

1190 80.0 g of seed 23 b is + ^ crogene grams) + 160 ml is H₂ 0 good mixing, filling in 8 hours in the autoclave at 300 °c on stainless steel vessel and tacked HgO 270 - 300 atmospheres and holding pressure.

Magn. data: br/p=447 / üü.g "¹ ^ / centimeters.

I IS_{THE HC} =■421 Z is '/ ond

Example 24

a is) precursor

67.17 g of finely divided cr0 (0h) - moremore pui.ver (82.9 ^{a is} residual Of Cr₂ from 0 ^) + 47.165 felnteHLges g of tellurium powder (99.1 DEGREES/DEGREES Th) in the ratio of the compound Ci'gTeOg good mixing.

b is) imbiidurig sketch

^ - F is - 24 a is crogene ii90 g of whole precursor) + 20 ml is H_? 0 good mixing, into a EDU tahtah.lgefä L (3 hours in the autoclave filling and d

el, 0 at 280° u and 200 - 230 GB pressure maintained.

C IS -

Magn. data: brrYY> ^=296/g.g cm7 - 1.

I IS_{IS H} is O=³²⁹№

c is) Pigment formation

1190 80.0 g of seed 24 b is + ^ Selezione grams) + 160 ml HgO good mixing, filling into a stainless steel vessel and 8 hours in the autoclave at 550 h2o on^{is O} G and holding 270 - 300 atmospheres pressure.

Magn. data: brr/ Y is 478/g.g="¹ cms.

I IS_{The HC} =419 [Öj