Synthesis and electrophysical properties of cation conductors Sr3 − 3xLa2x(V1 − yPyO4)2 with palmierite structure

The solid solutions Sr2.4La0.4(V1 − yPyO4)2 with palmierite structure were synthesized and characterized. The electrical conductivity was measured depending on temperature and partial pressure of oxygen. Both studies were carried out in the range of partial oxygen pressure 10− 15− 0.5atm at temperatures 400–1200°C. Thermal expansion tests were carried out in air within 20–1200°C. The cation transport over Sr2 positions is responsible for the ion conductivity below 950 °C. The disordering of palmierite structure in Sr2.4La0.4(V1 − yPyO4)2, where y ≥ 0.3, near 1000 °C is accompanied by the conductivity increase in about two times and by the decrease of thermal expansion coefficient. These changes are explained as manifestation of interstitial strontium cations. The substitution of vanadium by phosphorus results in the increase in thermodynamic stability.