Sintering and electrical properties of Na0.5K0.5NbO3 ceramics modified with lanthanum and iron oxides

Effects of La3+, Fe3+ doping and their co-doping on the sintering, structures and electrical properties of Na0.5K0.5NbO3 (NKN) ceramics were investigated. A significant modification of sintering behavior can be obtained by the addition of Fe2O3. On the contrary, the addition of La2O3 and La–FeO3 tends to degrade the densification. Moreover, Fe3+ doping does not change the crystal structure, thus leading to an unchanged Curie temperature. Owing to a transition from orthorhombic to pseudo-cubic structures, the Curie temperatures of NKN ceramics were significantly lowered by doping La2O3 and La–FeO3. NKN ceramics modified with a small amount of Fe2O3 and La–FeO3 (less than 0.5 mol%) exhibit improved ferroelectric, piezoelectric and electromechanical properties.