US 5,453,262 A · Continuous process for production of ceramic powders with controlled morphology

Abstract

A continuous process for making a crystalline ceramic powder having a perovskite structure, ABO.sub.3, 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.

Claims33

Dependent claims

A continuous process for making a crystalline ceramic powder having a perovskite structure, ABO.sub.3, 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.

7 more elements

A continuous-process for making a crystalline ceramic powder having a perovskite structure, ABO.sub.3, 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.degree. C. to about 70.degree. 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.degree. C. and 90.degree. 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.degree. C. and 240.degree. C., at a pressure between about 350 psi to about 510 psi for a time sufficient to form the powder.

7 more elements

A continuous process for making crystalline ceramic particles having a perovskite structure, ABO.sub.3, 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.

6 more elements

A process for making a crystalline ceramic powder having a perovskite structure, ABO.sub.3, 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.

6 more elements

Dependencies are inferred from the claim text.

Continuous process for production of ceramic powders with controlled morphology

Life of this patent

Continuous process for production of ceramic powders with controlled morphology

Life of this patent

Abstract

Claims33