Phase transformations and thermal stability of Ni-doped BiNbO4 ceramics

Abstract

Phase transformations and thermal stability of nickel-containing solid solutions of bismuth orthoniobate BiNbO4 were studied by methods of thermal and X-ray phase analysis. The DSC curve of the BiNb1-xNixO4-δ samples exhibited endothermic effects near the temperatures of 1049 °C and 1227 °C during the heating, and exothermic effects at ˜990 °C during the cooling, which were associated with the phase transition from the orthorhombic to triclinic modification and with congruent melting. In the compacted polycrystalline samples of the solid solutions, the phase transition from the high-temperature triclinic modification to the orthorhombic modification was revealed after calcination at 750 °C for 150 h, as well as after 1 h calcination at 950 °C.