Phase Transition Character and Electrical Properties of Rhombohedral 0.95Pb(Zn1/3Nb2/3)O3–0.05PTiO3 Single Crystals

Large-size and high-quality 0.95Pb(Zn1/3Nb2/3)O3–0.05PbTiO3 (0.95PZN–0.05PT) single crystals were grown by a modified Bridgman method using an allomeric 0.69Pb(Mg1/3Nb2/3)O3–0.31PbTiO3 single crystal as a seed. The as-grown 0.95PZN–0.05PT single crystals exhibit rhombohedral perovskite structure, which changes wholly into cubic structure at 165 °C confirmed by high-temperature X-ray diffraction measurement. 0.95PZN–0.05PT exhibits broad and diffused dielectric response peaks accompanied by apparent dielectric frequency dispersion. Polarization induces an additional dielectric anomaly around 109 °C accompanied by the increase of the temperature of dielectric maximum ($T_{\text{m}}$), decrease of the value of dielectric maximum ($\varepsilon_{\text{m}}$) and the enhancement of frequency dispersion which can be assigned to the orientation of ferroelectric domain or a macro–micro domain transition upon heating. The [001]-oriented 0.95PZN–0.05PT crystals exhibit excellent electrical properties, where remanent polarization $P_{\text{r}}$ is 36.89 μC/cm2 and piezoelectric constant $d_{33}$ is around 1120–1180 pC/N. Pyroelectric coefficient $ p$, detectivity and voltage responsivity figures of merit $F_{\text{d}}$ and $F_{\text{v}}$ of the 0.95PZN–0.05PT single crystals are 458 μC/(K$\cdot$m2), 6.027 μPa-1/2, and 0.0125 m2/C, respectively, which increase greatly over the temperature range measured. It is needed to improve temperature stability and voltage responsivity to meet the requirements of practical applications. 0.95PZN–0.05PT exhibits rather high transparency, with the ultraviolet cut-off edge near 385 nm indicating a low-lying electronic energy gap of ${\sim}3.12$ eV. The infrared-absorption band occurs at 595 cm-1, which can be attributed to the normal vibration of [Zn1/3Nb2/3]/TiO3 group.