An investigation on phase transition behaviors in MgO-doped Pb_(0.99)(Zr_(0.95)Ti_(0.05))_(0.98)Nb_(0.02)O_3 ferroelectric ceramics by Raman and dielectric measurements

摘要

The phase transition behaviors of Pb_(0.99)(Zr_(0.95)Ti_(0.05))_(0.98)Nb_(0.02)O_3 ferroelectric ceramics doped with different MgO concentrations (0-0.2 wt%) were systematically investigated by Raman and dielectric measurements. Raman results showed that the phase transitions were strongly dependent on MgO concentration. It was found that the low temperature rhombohedral (F_(R(LT)))-high temperature rhom-bohedral (F_(R(HT))) ferroelectric phase transition shifted toward a lower temperature with increasing MgO concentration up to 0.1 wt%, while the F_(R(HT))-cubic paraelectric (P_C) phase transition changed to a higher temperature. The Raman results were in good agreement with phase transition determined by dielectric measurements. Moreover, it was indicated that the changes of Raman active modes were related to distortion of BO_6 octahedra during the phase transitions. Then, the distortion of BO_6 octahedron caused by B-site replacement of Mg~(2+) ions was proposed to explain the observed behaviors. In addition, the effects of MgO doping on the dielectric, ferroelectric and pyroelectric properties were also discussed.