Na_(1/2)Bi_(1/2)TiO_(3)-based materials exhibit potential for applications in high-power ultrasonics.The com-posites of Na_(1/2)Bi_(1/2) TiO_(3)-yBaTiO_(3)(NBTyBT;y denotes mole%)with ZnO inclusions were demonstrated ...Na_(1/2)Bi_(1/2)TiO_(3)-based materials exhibit potential for applications in high-power ultrasonics.The com-posites of Na_(1/2)Bi_(1/2) TiO_(3)-yBaTiO_(3)(NBTyBT;y denotes mole%)with ZnO inclusions were demonstrated to stabilize a ferroelectric equilibrium that led to enhanced thermal depolarization temperature(T_(d))and increased mechanical quality factor(Q_(m)).This work addresses the influence of the matrix NBTyBT phase by investigating two limiting choices based on symmetry(tetragonal/rhombohedral)and polar(relaxor/ferroelectric)nature.While the composites constituting the tetragonal NBT9BT(non-ergodic relaxor at room temperature)matrix phase exhibit improved T d,the critical temperatures in the composites with rhombohedral NBT3BT(displaying spontaneous ferroelectric order at room temperature)exhibit only marginal changes.Further,NBT3BT composites feature a 45%increase in Q m,while the corresponding increase is roughly three-fold for the NBT9BT composites.A 3-D Finite Element Method is used to simulate the electric field gradient at the matrix/inclusion interface,with the effective field distribution estimated to be higher than the applied field for highly conducting ZnO inclusions.The electrical properties indicate that,while the deviatoric stress at the matrix/inclusion interface stabilizes the ferroelectric equilibrium for the relaxor matrix phase,the stresses disrupt the long-range order for the ferroelectric matrix phase.These results establish the volume-limit of the second phase to stabilize a ferroelectric equilibrium,in addition to substantiating the role of residual stress evidenced by changes in the polar nature.Finally,a comparison of the composites with different NBTyBT phases is presented,with NBT6BT:ZnO composites demonstrating an optimal increase in both T_(d) and Q_(m).展开更多
文摘Na_(1/2)Bi_(1/2)TiO_(3)-based materials exhibit potential for applications in high-power ultrasonics.The com-posites of Na_(1/2)Bi_(1/2) TiO_(3)-yBaTiO_(3)(NBTyBT;y denotes mole%)with ZnO inclusions were demonstrated to stabilize a ferroelectric equilibrium that led to enhanced thermal depolarization temperature(T_(d))and increased mechanical quality factor(Q_(m)).This work addresses the influence of the matrix NBTyBT phase by investigating two limiting choices based on symmetry(tetragonal/rhombohedral)and polar(relaxor/ferroelectric)nature.While the composites constituting the tetragonal NBT9BT(non-ergodic relaxor at room temperature)matrix phase exhibit improved T d,the critical temperatures in the composites with rhombohedral NBT3BT(displaying spontaneous ferroelectric order at room temperature)exhibit only marginal changes.Further,NBT3BT composites feature a 45%increase in Q m,while the corresponding increase is roughly three-fold for the NBT9BT composites.A 3-D Finite Element Method is used to simulate the electric field gradient at the matrix/inclusion interface,with the effective field distribution estimated to be higher than the applied field for highly conducting ZnO inclusions.The electrical properties indicate that,while the deviatoric stress at the matrix/inclusion interface stabilizes the ferroelectric equilibrium for the relaxor matrix phase,the stresses disrupt the long-range order for the ferroelectric matrix phase.These results establish the volume-limit of the second phase to stabilize a ferroelectric equilibrium,in addition to substantiating the role of residual stress evidenced by changes in the polar nature.Finally,a comparison of the composites with different NBTyBT phases is presented,with NBT6BT:ZnO composites demonstrating an optimal increase in both T_(d) and Q_(m).
