Fabrication and negative thermal expansion properties of P-substituted ZrV2O7 sintered bodies

Calcined powders of ZrV1.2P0.8O7 (ZVP) and ZrV2O7 (ZV) were synthesized by heating gels prepared from NH4H2PO4, NH4VO3, and ZrOCl2 solutions at 500 and 400 degrees C, respectively. Dense ZV-added ZVP sintered bodies were subsequently fabricated through heating at 850 degrees C for 20 h, with the addition of ZrV2O7 as a sintering additive. The resulting material had a relative density of ca. 92%, while the relative density of pure sintered ZVP was ca. 72%. NH4H2PO4 (NHP) was also added to ZVP along with ZV to obtain a molar ratio of P in NHP for V in ZV = 1. Subsequently, a single phase (NHP, ZV)-added ZVP sintered body was obtained by heating at 850 degrees C. Thermomechanical analysis showed that the dense ZV-added ZVP sintered body exhibited a positive thermal expansion from 25 to 150 degrees C and a negative thermal expansion from 150 to 500 degrees C.