Process for producing perovskite type complex oxide precipitates

A process for producing perovskite structure complex oxide precipitates represented by the formula (I):

• M.sup.1.sub.x M.sup.2.sub.y O.sub.z (I)
• wherein M.sup.1 represents at least one metal selected from the group consisting of a rare earth metal and an alkaline earth metal atom optionally along with an alkali metal atom, M.sup.2 represents at least one metal selected from the group consisting of a transitional metal and a IIA group metal atom of the periodic table optionally along with an alkaline earth metal atom, x, y and z are each a number making said oxide electrically neutral, which process comprises:
• (a) forming an aqueous solution or hydrofluoric acid solution containing
• (1) at least one compound selected from the group consisting of
• (i) metal fluoro complex compounds represented by the formula (II):
• A.sub.a M.sup.1.sub.b F.sub.c (II)
• wherein A represents a hydrogen atom, an alkali metal atom, an ammonium group or coordinated water;
• M.sup.1 has the same meaning as defined above;
• a, b and c are each a number of 1 or more;
• when b is 1, a is a number obtained by subtracting the valence of M.sup.1 from c, and when a is two or more, the A's are the same or different from each other and when b is two or more, the M's are the same or different from each other;
• and
• (ii) a metal fluoride which excludes the metal fluoro complex compound of formula (II) and is at least one metal fluoride selected from the group consisting of beryllium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride and rare earth metal fluorides optionally along with an alkali metal fluoride;
• and
• (2) at least one compound selected from the group consisting of
• (i) metal fluoro complex compounds represented by the formula (III):
• A.sub.d M.sup.2.sub.e F.sub.f (III)
• wherein A and M.sup.2 have the same meanings as defined above, d, e and f are each a number of 1 or more;
• when e is 1, d is a number obtained by subtracting the valence of M.sup.2 from f, when d is two or more the A's are the same or different from each other and when e is two or more, the M.sup.2 's are the same or different from each other, and
• (ii) a metal fluoride selected from the group consisting of transition metal fluorides and fluorides of group IIIA metals of the periodic table, optionally along with an alkaline earth metal fluoride selected from the group consisting of beryllium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride and barium fluoride, and
• (b) adding at least one of a fluoride ion-capturing agent selected from the group consisting of boric acid, borates, sodium hydroxide, aqueous ammonia, aluminum, titanium, iron, nickel, magnesium, copper, zinc, glass, silicon, calcium oxide, boron oxide, aluminum oxide, silicon dioxide, magnesium oxide in a homogeneous state or heterogeneous state to the resulting mixed solution in an amount sufficient to cause precipitation of the perovskite structure complex oxide to form said complex oxide precipitates having the metal atoms M.sup.1 and M.sup.2.