Original paper

Isomorphous substitutions in vanadate garnets

Iishi, K.; Ikuta, Y.

Abstract

Experiments were conducted to synthesize vanadate garnets of the following 5 types; Type 3: {A+2A2+}[M2+M3+] (V3)O12, Type 4: {A+A2+2}[M+M3+](V3)O12, Type 5: {A+A2+2}[M2+2](V3)O12, Type 6: {A2+3}[M+M2+](V3)O12 and Type 7: {□0.5 A2+2.5}[M2+2](V3)O12, where A+ = Li+, Cu+, Na+, Ag+ and K+; A2+ = Cd2+, Ca2+, Sr2+ and Pb2+; M+ = Li+; M2+ = Ni2+, Mg2+, Co2+, Cu2+, Zn2+, Mn2+ and Cd2+; M3+ = Cr3+ and Fe3+. New variations of {Na2Ca}[NiFe3+](V3)O12, {A+Ca2} [LiCr3+](V3)O12, where A+ = Li+ and Na+, {A+ Ca2}[LiFe3+](V3)O12, where A+ = Li+, Cu+, Na+ and Ag+, {LiCa2}[M2+2](V3)O12, where M2+ = Co2+ and Mn2+, {KCa2}[Mn2](V3)O12, {Ca3}[LiCd](V3)O12 and {Pb3}[LiM2+](V3)O12, where M2+ = Mg2+, Co2+, Zn2+, Mn2+ and Cd2+ were prepared as phase-pure garnets for the first time. Garnets were formed only a few in both types 3 and 4. In types 5, 6 and 7, the variety of garnets formed was greatly limited by the replacement of Ca2+ by Sr2+ as compared with that being not so much limited by the replacement of Ca2+ by Pb2+, though the effective ionic radius of Pb2+ is larger than that of Sr2+. This is ascribed to "the hard and soft acids and bases principle". In types 5, 6 and 7, in the case of M2+ = Cu2+, the variety of garnets formed was fairly limited due to the "the Jahn–Teller effect of Cu2+".

Keywords

vanadate garnetsynthesissubstitutioncell parametertransition metal ionjahn-teller effecthard and soft acids and bases principle