An investigation into group 13 (Al, Ga, In) substituted (Na0.5Bi0.5)TiO3-BaTiO3 (NBT-BT) lead-free piezoelectrics

Ternary phase diagrams were explored for the systems (Na0.5Bi0.5)TiO3-BaTiO3-Bi(M)O3 M = Al, Ga, In to determine periodic trends as a function of substitution. The ferroelectric and piezoelectric properties were measured and compared to (Na0.5Bi0.5)TiO3-BaTiO3 (NBT-BT). X-ray synchrotron and neutron diffraction data were collected to determine the changes in structure as a function of substitution. Data showed that most systems behave in a similar manner to the parent (Na0.5Bi0.5)TiO3-BaTiO3. However, two specific compositions display interesting properties: the 2% BiGaO3 (BG2) substituted sample and the 4% BiAlO3 (BA4) substituted sample. The BG2 sample undergoes an irreversible electric-field induced phase transition, as seen in NBT-BT, but has a significantly larger high-field strain. The BA4 composition has a different strain mechanism than all the other composition studied. It displays incipient piezoelectricity which results in a giant high-field strain due to a reversible phase transition. This study highlights the difficulty in trying to improve the properties of the highly disordered NBT-BT material.