High-temperature properties of the solid solution BaNi2(V1−xPxO4)2

Abstract

The polycrystalline samples of BaNi2(V1−xPxO4)2 (x ​= ​0–1) were prepared via a solution combustion synthesis. The study of the crystal structure shows that the substitution of vanadium (5+) cations by smaller phosphorus (5+) cations leads to compression of the [Ni2(V1−xPxO4)2]∞ layers in the ab plane with a decrease in the unit cell volume of BaNi2(V1−xPxO4)2. As a result, the BaO12 polyhedra are elongated along the c axis. The melting point increases monotonically with increasing phosphorus concentration. The linear dependence of the relative elongation (ΔL/L0) of samples on temperature after 500 ​°C becomes S-shaped. The electrical conductivity (σ) of BaNi2(V1−xPxO4)2 was measured in the range of 300–900 ​°C. Electron transfer in BaNi2(V1−xPxO4)2 established to occur along the Ni–O–Ni chains and is explained by the formation of Ni3+.