Niobate perovskite oxides of KNb1–xMgxO3–δ were synthesized directly at high temperature and pressure. The use of X-ray diffraction confirmed the formation of single-phase orthorhombic structures. High-temperature Raman spectroscopy, together with thermal analysis, showed that phase transitions occurred from orthorhombic to tetragonal, to pseudo cubic, and finally to cubic, in sequence. The addition of Mg2+ at Nb5+ sites of the perovskite lattice led to a marked enhancement of oxide-ion conduction. This enhancement in conduction was due to suppression of the contribution arising from p-type holes.

Activation of Oxide-Ion Conduction in KNbO3 by Addition of Mg2+. L.Li, G.Li, R.L.Smith, H.Inomata: Applied Physics Letters, 2002, 81[15], 2899-901