Process for producing a composition which includes perovskite compounds

A process for producing a composition which includes a perovskite compound, the process comprising:

• (a) subjecting a mixture of a hydroxide of at least one A group element selected from the group consisting of Mg, Ca, Sr, Ba, Pb and rare earth elements and a hydroxide of at least one B group element selected from the group consisting of Ti, Zr, Hf and Sn, to the hydrothermal reaction in an aqueous reaction medium;
• (b) filtering, washing with water and drying the resultant reaction mixture to provide a solid reaction product, dispersing the reaction product in an aqueous medium to form a slurry, adding to the slurry a water-insoluble compound of the A group element so as to adjust the ratio of the group A element to the group B element in a resulting composition to a desired A/B ratio;
• and
• (c) filtering, washing and drying the resultant mixture to provide the composition which includes the perovskite compound having the desired A/B ratio.

A process for producing a sintered body which is substantially composed of a perovskite compound of desired atomic ratios, the process comprising:

• (a) subjecting a mixture of a hydroxide of at least one A group element selected from the group consisting of Mg, Ca, Sr, Ba, Pb and rare earth elements and a hydroxide of at least one B group element from the group consisting of Ti;
• Zr, Hf and Sn, to the hydrothermal reaction in an aqueous reaction medium;
• (b) adding an insolubilizing agent to the resultant reaction mixture to insolubilize water-soluble compounds of the unreacted A group element dissolved in the aqueous medium so as to adjust the ratio of the group A element to the group B element in a resulting composition to a desired A/B ratio;
• or
• (c) filtering, washing with water and drying the resultant reaction mixture to provide a solid reaction product, dispersing the reaction product in an aqueous medium to form a slurry, adding to the slurry a water-soluble compound of the A group element, and then adding to the slurry an insolubilizing agent to insolubilize the water-souble compound of the A group element so as to adjust the ratio of the group A element to the group B element in a resulting composition to a desired A/B ratio;
• and
• (d) filtering, washing and drying the resultant mixture to provide the composition which includes the perovskite compound having the desired A/B ratio;
• and then
• (e) sintering the composition at temperatures from about 1100.degree. C. to about 1300.degree. C.

A process for producing a sintered body which is substantially composed of a perovskite compound of desired atomic ratios, the process comprising:

• (a) subjecting a mixture of a hydroxide of at least one A group element selected from the group consisting of Mg, Ca, Sr, Ba, Pb and rare earth elements and a hydroxide of at least one B group element selected from the group consisting of Ti, Zr, Hf and Sn, to the hydrothermal reaction in an aqueous reaction medium;
• (b) filtering, washing with water and drying the resultant reaction mixture to provide a solid reaction product, dispersing the reaction product in an aqueous medium to form a slurry, adding to the slurry a water-inoluble compound of the A group element so as to adjust the ratio of the group A element to the group B element in a resulting composition to a desired A/B ratio;
• (c) filtering, washing and drying the resultant mixture to provide the composition which includes the perovskite compound having the desired A/B ratio;
• and
• (d) sintering the composition at temperatures from about 1100.degree. C. to about 1300.degree. C.