Method of making highly sinterable lanthanum chromite powder

A method of making a highly sinterable lanthanum chromite powder containing a dopant metal, comprising the steps:

• (1) separately dissolving a La source, a Cr source and a source of a dopant metal selected from the group consisting of Ca, Sr, Co, Ba, Mg, and mixtures thereof, in a mixture of an acid selected from the group consisting of polycarboxylic acids, hydroxy acids and mixtures thereof, and a polyhydroxy alcohol, to form a solution of each;
• (2) evaporating a substantial amount of each of the solutions formed in step (1), and any precipate formed is filtered out of the solutions;
• (3) mixing the solutions together in the desired proportions to achieve a desired ratio of La, Cr and dopant metal, heating the solution mixture to reduce alcohol content and then further heating under a vacuum condition until esterification and polymerization occur, to form submicron polymer precipitates;
• (4) continuing heating the solution mixture under a vacuum condition until a foamed, porous mass of amorphous organic polymeric material forms;
• (5) heating the foamed amorphous polymeric material to burn off organic components and produce a hard, somewhat porous, charred material comprising La, Cr, and dopant metal;
• (6) grinding the somewhat porous charred material to a powder;
• (7) heating the somewhat porous, charred, ground powder at from 590.degree. C. to 950.degree. C., in a flowing atmosphere of inert gas containing from 100 ppm to 50,000 ppm O.sub.2 and less than 300 ppm CO.sub.2, for a time effective to provide a sinterable material having a high specific surface area of from 7 m.sup.2 /g to 30 m.sup.2 /g, consisting essentially of LaCrO.sub.3, containing from 5 weight % to 20 weight % of a chromite of the dopant metal;
• (8) adding the high specific surface area sinterable material solids to an aqueous solution mixture of a nitrate of Cr and a nitrate of a dopant metal selected from the group consisting of Ca, Sr, Co, Ba, Mg, and mixtures thereof, to form a slurry, where the total nitrate is added in an amount effective to provide from 3 weight % to 20 weight % dopant metal chromate upon subsequent evaporation and heating in step (11);
• (9) grinding the particles in the slurry to provide particles of a sinterable material having a diameter up to 3 micrometers in the slurry;
• (10) taking the nitrate slurry with the ground particles and simultaneously evaporating solvent and coating the particles of sinterable material with a solidified mixture of nitrates, to provide dry, coated particles;
• and
• (11) heating the dry, coated particles at a temperature effective to convert the nitrate coating to a chromate coating, where the chromate coating constitutes from 3 weight % to 20 weight % of the total weight of the coated particles, to provide a highly sinterable powder having a high specific surface area of from 7 m.sup.2 /g to 30 m.sup.2 /g.