High Solubility of Hetero-Valence Ion (Cu2+) for Reducing Phase Transition and Thermal Expansion of ZrV1.6P0.4O7

Large thermal expansion at room temperature and high phase transition temperature of ZrV2O7 limit its practical applications and are reduced by the high solubility of hetero-valence ion (Cu2+) on the basis of an equal-valence substitution of P5+ for V5+. The temperature-dependent Raman spectra show that Zr0.9 Cu0.1 V1.6 P0.4 O6.9 maintains a normal parent cubic structure till 173K and transforms to a 3 × 3 × 3 cubic superstructure below 173K. Temperature dependent x-ray diffraction patterns of Zr0.9 Cu0.1 V1.6 P0.4 O6.9 show near zero and negative thermal expansion. High solubility of lower valence Cu2+ relates to an equal-valence substitution of smaller P5+ for V5+, which extends the bond angle of V(P)—O—V in ZrV1.6 P0.4 O7 close to 180°. The change of microstructure is considered to be responsible for reduced phase transition temperature and thermal expansion.