Continuous process for production of ceramic powders with controlled morphology

• US 5,453,262 A
• Filed: 06/10/1992
• Issued: 09/26/1995
• Est. Priority Date: 12/09/1988
• Status: Expired due to Fees

• Current Assignee: Nextech Materials, Ltd.
• Original Assignee: Battelle Memorial Institute
• Inventors: Swartz, Scott L., Dawson, William J.
• Primary Examiner(s): GREEN, ANTHONY J
• Application Number:
  US07/896,773
• Time in Patent Office: 1,203 Days
• Field of Search: 252/62.9, 252/62.9 PZT, 501/134, 501/135, 501/136, 501/137, 501/138, 501/139, 423/593, 423/598, 423/594, 423/595, 423/599
• US Class Current: 501/124
• CPC Class Codes: C04B 35/4682 based on BaTiO3 perovskite phase
• CPC Class Codes: C04B 35/472 based on lead titanates
• CPC Class Codes: C04B 35/486 Fine ceramics
• CPC Class Codes: C04B 35/491 based on lead zirconates and lead titanates , e.g. PZT
• CPC Class Codes: C04B 35/497 based on solid solutions with lead oxides
• CPC Class Codes: C04B 35/626 Preparing or treating the powders individually or as batches pigments for ceramics C09C1/0009; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B

Abstract

A continuous process for making a crystalline ceramic powder having a perovskite structure, ABO₃, comprising:

a. preparing a first acidic aqueous solution containing one or more elements that are insoluble precursor elements capable of forming the perovskite structure;

b. preparing a second basic solution containing a sufficient concentration of hydroxide to precipitate the elements in step (a);

c. mixing the first acidic solution with the second basic solution to precipitate a substantially pure mixture of hydroxides;

d. washing the precipitate to remove hydroxide and salt impurities;

e. forming a slurry of oxides or hydroxides of one or more of the elements that are soluble precursor elements capable of forming in the perovskite structure, and heating the slurry to a temperature sufficient to dissolve the soluble oxides or hydroxides of the soluble precursor elements;

f. redispersing the washed precipitate and heating to the temperature of the soluble oxides or hydroxides of step (e);

g. mixing solubilized oxides or hydroxides of step (e) with the heated slurry of step (f);

h. prereacting the third aqueous slurry at temperature, pressure, concentration, and for a time necessary to obtain the desired powder morphology; and

i. hydrothermally treating the pre-reacted solution in a continuous reactor at an elevated temperature and pressure for a time sufficient to form the powder.

Claims

1. A continuous process for making a crystalline ceramic powder having a perovskite structure, ABO₃, comprising:

(a) preparing a first acidic aqueous solution containing one or more elements that are insoluble precursor elements capable of forming the perovskite structure;

(b) preparing a second basic aqueous solution containing a sufficient concentration of hydroxide to precipitate the elements selected in step (a);

(c) mixing the first acidic solution with the second basic solution to precipitate a substantially pure mixture of hydroxides;

(d) washing the precipitate to remove hydroxide and salt impurities;

(e) forming an aqueous slurry of soluble oxides or hydroxides of one or more soluble precursor elements capable of forming the perovskite structure, and heating the slurry to a temperature sufficient to dissolve the soluble oxides or hydroxides of the soluble precursor elements;

(f) redispersing the washed precipitate of step (d) with water and heating to the temperature of the soluble oxides or hydroxides of step (e);

(g) mixing solubilized oxides or hydroxides of step (e) with the heated slurry of step (f);

(h) pre-reacting the mixed slurry of step (g) at a temperature, pressure, concentration, and for a time necessary to control powder morphology obtained in step (i); and

(i) hydrothermally treating the pre-reacted slurry in a continuous reactor at an elevated temperature and pressure for a time sufficient to form the powder.

2. The process according to claim 1, wherein the powder is separated, washed, and dried.

3. The process according to claim 1, wherein the heating in step (e) is at a temperature between about room temperature to about 70°

C.

4. The process according to claim 3, wherein the heating in step (e) is at a temperature between about 50°

C. to about 70°

C.

5. The process according to claim 1, wherein the pre-reacting step (h) is at a temperature above about 70°

C.

6. The process according to claim 5, wherein the pre-reacting step (h) is at a temperature between about 70°

C. and 90°

C.

7. The process according to claim 1, wherein the temperature for the hydrothermal treating step (i) is between about 210°

C. and 240°

C., and the pressure is between about 350 psi to about 510 psi.

8. The process according to claim 7, wherein the time for treatment of the pre-reacted solution within the continuous reactor of step (i) is less than 30 minutes.

9. The process according to claim 7, wherein the time for treatment of the pre-reacted solution within the continuous reactor of step (i) is less than 15 minutes.

10. The process according to claim 1, wherein the insoluble precursor element comprises titanium and the soluble precursor element comprises barium.

11. The process according to claim 10, wherein the temperature for the hydrothermal treating step (i) is between about 210°

C. and 240°

C., and the pressure is between about 350 psi to about 510 psi.

12. The process of claim 1, further comprising:

prereacting the slurry in step (h) to obtain a powder having a particle size between about 0.05 to about 1.0 microns.

13. A continuous-process for making a crystalline ceramic powder having a perovskite structure, ABO₃, comprising:

(a) preparing a first acidic aqueous solution containing one or more elements that are insoluble precursor elements capable of forming the perovskite structure, wherein an insoluble precursor element comprises titanium and dopants are selected from the group consisting of hafnium, zirconium, niobium, tantalum, uranium, iron, antimony, lanthanum, bismuth, thorium, indium, nickel, manganese, neodymium, samarium, cobalt, tungsten, tin, vanadium, dysprosium, praseodymium, yttrium, promethium, europium, cerium, ytterbium, lutetium, scandium, gadolinium, terbium, holmium, erbium, thulium, chromium, potassium, and lithium;

;

(b) preparing a second basic solution containing a sufficient concentration of hydroxide to precipitate the elements selected in step (a);

(c) mixing the first acidic solution with the second basic solution to precipitate a substantially pure mixture of hydroxides;

(d) washing the precipitate to remove hydroxide and salt impurities;

(e) forming a slurry of oxides or hydroxides of one or more elements that are soluble precursor elements capable of forming the perovskite structure, and heating the slurry to a temperature sufficient to dissolve the soluble oxides or hydroxides of the soluble precursor elements, wherein when a soluble precursor oxide or hydroxide of barium is used the temperature is between about 50°

C. to about 70°

C.;

(f) redispersing the washed precipitate and heating to the temperature of the soluble oxides or hydroxides of step (e);

(g) mixing the redispersed slurry of step (f);

(h) pre-reacting the mixed and redispersed slurry at a temperature between about 70°

C. and 90°

C., at atmospheric pressure, and at a concentration, and for a time necessary to control powder morphology in step (i); and

(i) hydrothermally treating the pre-reacted slurry in a continuous reactor at a temperature between about 210°

C. and 240°

C., at a pressure between about 350 psi to about 510 psi for a time sufficient to form the powder.

14. The process according to claim 13, wherein the powder is separated, washed, and dried.

15. The process according to claim 13, wherein the time for treatment of the pre-reacted solution within the continuous reactor of step (i) is less than 30 minutes.

16. The process according to claim 13, wherein residence time for treatment of the pre-reacted solution within the continuous reactor of step (i) is less than 15 minutes.

17. The process of claim 13, further comprising:

prereacting the slurry in step (h) to obtain a powder having a particle size between about 0.05 to about 1.0 microns.

18. A continuous process for making crystalline ceramic particles having a perovskite structure, ABO₃, comprising:

(a) preparing a first acidic solution containing one or more elements selected from the group consisting of hafnium, zirconium, titanium, niobium, tantalum, uranium, iron, antimony, lanthanum, bismuth, thorium, indium, nickel, manganese, neodymium, samarium, cobalt, tungsten, tin, vanadium, dysprosium, praseodymium, yttrium, promethium, europium, cerium, ytterbium, lutetium, scandium, gadolinium, terbium, holmium, erbium, thulium, chromium, potassium, and lithium;

(b) preparing a second basic solution containing a sufficient concentration of hydroxide to precipitate the elements selected in step (a) when mixed with the first solution;

(c) adding the first acidic solution to the second basic solution to precipitate a substantially pure mixture of hydroxides;

(d) washing the precipitate to remove hydroxide and salt impurities that solubilize lead or other constituent elements of the particles;

(e) preparing an aqueous slurry of the washed precipitate and adding oxides or hydroxides of one or more of the elements selected from the group consisting of barium, strontium, calcium, magnesium, lead, zinc, yttrium, manganese, cobalt, and nickel;

(f) mixing and heating the aqueous slurry of step (e) at a temperature where the washed precipitate from step (d) does not convert to an oxide, yet is sufficient to dissolve the oxides or hydroxides of elements selected in step (e);

(g) pre-reacting the mixed and heated slurry of step (f) at a temperature, pressure, concentration, and for a time sufficient to produce a selected particle morphology; and

(h) hydrothermally treating the slurry of step (g) in a continuous reactor at an elevated temperature and pressure for a time sufficient to form the particles.

19. The process according to claim 18, comprising the additional step of:

(i) cooling the hydrothermally treated slurry containing the particles, separating the particles, washing with purified water and drying.

20. The process according to claim 18, wherein the heating in step (f) is at a temperature between about room temperature to about 70°

C.

21. The process according to claim 20, wherein the heating in step (f) is at a temperature between about 50°

C. to about 70°

C.

22. The process according to claim 18, wherein the pre-reacting step (g) is at a temperature above about 70°

C.

23. The process according to claim 18, wherein the pre-reacting step (g) is at a temperature between about 70°

C. and 90°

C.

24. The process according to claim 18, wherein the temperature for the hydrothermal treating step (h) is between about 210°

C. and 240°

C., and the pressure is between about psi to about 600 psi.

25. The process according to claim 24, wherein the time for treatment of the pre-reacted solution within the continuous reactor of step (h) is less than 30 minutes.

26. The process according to claim 24, wherein the time for treatment of the pre-reacted solution within the continuous reactor of step (h) is less than 15 minutes.

27. The process according to claim 18, wherein a selected element in the acidic solution of step (a) comprises titanium and an oxide or hydroxide of barium is added in step (e).

28. The process according to claim 18, wherein the hydroxide of step (b) is selected from the group consisting of sodium hydroxide, ammonium hydroxide, and potassium hydroxide, with the proviso that when manganese, nickel, or cobalt are selected in step (a) ammonium hydroxide is not selected.

29. The process according to claim 18 wherein in step (c) the first acidic solution is added to the second basic solution to form a precipitate at a pH ranging from about 4 to about 12.

30. The process according to claim 18 wherein in step (e) the oxides or hydroxides are added to the aqueous slurry of the washed precipitate at a pH ranging from about 10 to about 13.

31. The process of claim 18, further comprising:

prereacting the slurry in step (g) to obtain a powder having a particle size between about 0.05 to about 1.0 microns.

32. A process for making a crystalline ceramic powder having a perovskite structure, ABO₃, comprising:

(a) dissolving one or more acidic salts of elements selected from the group consisting of hafnium, zirconium, titanium, niobium, tantalum, uranium, iron, antimony, lanthanum, bismuth, thorium, indium, nickel, manganese, neodymium, samarium, cobalt, tungsten, and tin, vanadium, dysprosium, praseodymium, yttrium, promethium, europium, cerium, ytterbium, lutetium, scandium, gadolinium, terbium, holmium, erbium, thulium, chromium, potassium, and lithium in an aqueous solution to form an acidic solution, wherein the acidic solution comprises the selected elements in a stoichiometry equal to step (g) stoichiometry;

(b) slowly adding the solution of step (a) to a vigorously mixed basic solution containing hydroxides of sodium, ammonium, and potassium wherein ammonium is not used when manganese, nickel, or cobalt are selected as an ingredient in step (a), until a pH value between 4 and 12 is reached in a range where all elements are essentially precipitated as hydroxides; and

where an equal or narrower pH range is selected which will provide incorporation of elements added in step (d);

(c) separating the precipitate from the solution and washing with purified water;

(d) redispersing the washed precipitate in water and mixing with the oxides or hydroxides of one or more of the elements selected from the group consisting of barium, strontium, calcium, magnesium, lead, zinc, yttrium, manganese, cobalt, and nickel in the proper ratio to obtain a mixture, wherein the mixture comprises the selected oxides or hydroxides in a stoichiometry equal to step (g) stoichiometry, whereby a homogeneous slurry is produced;

(e) mixing and heating the aqueous slurry of step (d) at a temperature where the washed precipitate from step (c) does not convert to an oxide, yet is sufficient to dissolve the oxide or hydroxide of elements selected in step (d);

(f) pre-reacting the mixed and heated slurry of step (e) at a temperature, pressure, concentration, and for a time sufficient to produce a selected powder morphology; and

(g) hydrothermally treating the slurry in a continuous reactor at a temperature, at a pressure, and for time sufficient to form the crystalline ceramic powder having a perovskite structure.

33. The process of claim 32, further comprising:

prereacting the slurry in step (f) to obtain a powder having a particle size between about 0.05 to about 1.0 microns.