The effect of Bi3+on the behavior of V5+of CaVIG in the solid state reaction process

It was found from the curves of reduced magnetization (σs)p/(σs)sversus the prefiring temperature Tp of BixY1.2-xCa1.8Sn0.3V0.5Ge0.5Fe3.7O12(x=0, 0.4, 0.8, 1.2) that some of these curves showed a peak value larger than 1, with the maximum value 1.2 for x=0. The σs-T curves for materials with x=0 at different Tp have much higher Tc than that of the sintering samples, and are not smooth, suggesting a superposition of many phases. The results demonstrate that the garnets with high σsand high Tc were first formed at lower temperature, and V⁵⁺, Sn⁴⁺, Ge⁴⁺ions gradually occupy d or a site only at higher temperature. It can also be seen from plot of (σs)p/(σs)s-Tp that (σs)p/(σs)s>1 died away with increasing x and vanished at x=1.2, The σs-T curves of prefiring samples with x=0.4 show a major phase (Tc=150°C) and a minor phase(Tc>200°C) and the curves of the prefiring samples with x=1.2 are smooth and give a common Tc (165 °C) equal to that of the sintering samples. The results show that Bi substitution is favourable for V⁵⁺Sn⁴⁺, Ge⁴⁺. ions to enter the garnet lattices.