(1 − x)Na0.5Bi0.5TiO3 − xK0.5Bi0.5TiO3 (NKBT100x; x being the mole ratio) piezoelectric ceramics were prepared by a conventional solid reaction method. The microstructure and ferroelectric properties of NKBT100x solid solution ceramics with compositions of Na0.5Bi0.5TiO3 (NBT)-rich and K0.5Bi0.5TiO3 (KBT)-rich were investigated by SEM, XRD, temperature dependence of dielectric constant, and hysteresis loop, respectively. XRD studies showed that the pure perovskite structure existed in NKBT100x ceramics with x ⩽ 0.50, while a small amount of a second phase, K4Ti3O8, appeared in the ceramics with x ⩾ 0.70 due to the structural instability of KBT-rich ceramics. The grain size decreased with increasing KBT content, showing that the KBT-rich solid solutions were very difficult to densify fully. The temperature dependence of the dielectric constant of NKBT100x ceramics showed that the depolarization temperature (Td) reached a minimum value at the composition of x = 0.16 (NKBT16) near the morphotropic phase boundary, which suggested that the ferroelectric state of co-existence between the rhombohedral phase of NBT and tetragonal phase of KBT were not as stable as the single phase of NBT and KBT, respectively. The poled density NKBT50 (x = 0.50) showed high piezoelectric properties, high Td and low dielectric loss, which was a good candidate for lead free piezoelectric ceramics working at relatively high temperatures.
The relaxor ferroelectrics—0.3Pb(Zn1∕3Nb2∕3)O3–0.7(Pb,La)(Zr,Ti)O3—have been produced by sintering in reductive nitrogen ambient and postannealing in oxygen ambient. The two kinds of specimens exhibited great differences in the conductivity as a function of temperature, which indicated a high concentration of oxygen vacancies in the as-sintered specimen. On the other hand, this specimen underwent an evident spontaneous normal-relaxation transition, whereas the as-annealed one did not. The corresponding reason has been analyzed on the basis of the facts, which provide some evidence that the interior stresses due to oxygen deficiency induce the spontaneous normal-relaxor transition in the specimen sintered in reductive ambient.
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