Phase transition and grain growth kinetics of V₂O₅ and B₂O₃ doped zinc titanate ceramics

Zinc titanate ceramics were prepared by the conventional mixed-oxide method combined with a chemical processing. The effects of V₂O₅-B₂O₃ additives on the low-temperature sintering behavior and phase structures of zinc titanate ceramics were investigated; and phase transition mechanism and grain growth kinetics were discussed. The results show that the densification temperature of zinc titanate ceramics can be reduced from 1100 to below 900°C by V₂O₅-B₂O₃ addition. The temperature of complete phase transition from hexagonal ZnTiO₃ phase to cubic Zn₂TiO₄ is lowered from 945 to 930°C for V₂O₅-B₂O₃ co-doped samples. Exaggerated grain growth found is in V-rich region in high-V content samples and disappeared with B₂O₃ content increasing, at the same time, the grains become uniform. V₂O₅-B₂O₃ additive increases the diffusion rate of structure unit and accelerates grains growth. The Tradition Phenomenological Rate Equation (TPRE) model is well fit for characterizing the grain growth kinetics of V₂O₅-B₂O₃ co-doped zinc titanate ceramics. According to TPRE, the grain growth activation energy calculated is 315.5 kJ/mol, the grain growth expression is shown as G = K₀ texp(-315.5 × 10³/RT)^2/7. The Q value decreases for V0-doped zinc metatitanate-based ceramics in microwave region as compared to single-phase hexagonal ZnTiO₃ ceramics. The value of dielectric constant depends on the amount of rutile phase from the decomposition of hexagonal ZnTiO₃ phase and the bulk density of ceramics.