Thermal depolarization and electromechanical hardening in Zn²⁺-doped Na1/2Bi1/2TiO3-BaTiO3

Abstract

Na
1/2Bi
1/2TiO
3-based materials have been earmarked for one of the first large-volume applications of lead-free piezoceramics in high-power ultrasonics. Zn
2+-doping is demonstrated as a viable route to enhance the thermal depolarization temperature and electromechanically harden (1-y)Na
1/2Bi
1/2TiO
3-yBaTiO
3 (NBT100yBT) with a maximum achievable operating temperature of 150 °C and mechanical quality factor of 627 for 1 mole % Zn
2+-doped NBT6BT. Although quenching from sintering temperatures has been recently touted to enhance T
F-R, with quenching the doped compositions featuring an additional increase in T
F-R by 17 °C, it exhibits negligible effect on the electromechanical properties. The effect is rationalized considering the missing influence on conductivity and therefore, negligible changes in the defect chemistry upon quenching. High-resolution diffraction indicates that Zn
2+-doped samples favor the tetragonal phase with enhanced lattice distortion, further corroborated by
23Na Nuclear Magnetic Resonance investigations.