Destabilization of ferroelectric order in Na0.5Bi0.5TiO3–6 wt% BaTiO3 ceramics

After 15 years of intensive investigations to replace lead-based materials in piezoelectric applications a breakthrough in still lacking. One of the most promising materials are Na0.5Bi0.5TiO3 (NBT)-based materials exhibiting... [ view full abstract ]

After 15 years of intensive investigations to replace lead-based materials in piezoelectric applications a breakthrough in still lacking. One of the most promising materials are Na_0.5Bi_0.5TiO₃ (NBT)-based materials exhibiting incipient piezoelectric effect. We investigated the solid-state synthesis of the composition NBT–6 wt% BaTiO₃ (NBT–6BT) modified with potassium, sodium, bismuth and/or niobium oxides. The different combinations of the dopant metal oxides were used to reveal the influence of individual substitutions of the cations on the A- and B-sites of the structure on the microstructure and electrical properties of bulk ceramics. While the substitution of Na/Bi with Ba at the A-site is not adequate to destabilize ferroelectric order, simultaneous doping of A- and B-sites with ions of different ionic radii triggers incipient piezoelectric properties. The investigation revealed that the resulting electrical properties are very sensitive to the stoichiometry; using starting chemicals of different purity or humidity content can inhibit the transition from ferroelectric to relaxor phase normally observed in composition 92NBT–6BT–2KNN. Any excess of alkali elements, especially potassium, results in increased leakage conductivity and electrical breakdown during polarization. In the contribution, data on the microstructure, stoichiometry, dielectric, ferroelectric, piezoelectric properties will be presented.