Piezoelectric Properties of Microwave-Sintered (Pb0.76Ca0.24)[(Co0.5W0.5)0.04Ti0.96]O3 Ceramics

Abstract

In this paper, (Pb0.76Ca0.24)[(Co0.5W0.5)0.04Ti0.96]O3 (PCCWT) ceramics were prepared using a mixed oxide method and sintered by means of microwave sintering (MS) and conventional sintering (CS) techniques. The electrical properties of PCCWT ceramics were evaluated via an impedance/gain phase analyzer and the corresponding microstructures were examined using scanning electron microscope (SEM). The experimental results show that the specimens using CS process need 1200°C-2 hr to reach the 95% relative density; however, the MS method required only 1150°C-15 min. Energy dispersion spectrum (EDS) data reveals that loss of PbO was significant in CS specimens, and therefore excess PbO were added to compensate to the nominal values. The polarization-electrical field (P-E) properties of CS and MS specimens also show that the coercive fields (E c ) of specimens decrease with the sintering temperature; however the remanent polarization (P r ) increased with the sintering temperature firstly and then decreased later, indicating two competition mechanisms exist. X-ray diffraction of specimens indicates that tetragonality of specimens decreases as the sintering temperature increases, implying that domain switchability is lower for lower temperature sintered specimen due to larger tetragonality. For higher temperature sintered specimens, the net polarization is smaller, although domains are easier to switch. Result of competition of the amount of domain switching and spontaneous polarization value produces a polarization maximum at a most suitable processing condition. Comparison of electric properties, the CS specimens (1200°C-2 hr) show the remanent polarization (P r ) of 26.5 μC/cm2, coercive field (E c ) of 16.4 kV/cm and electromechanical coupling coefficient (k t ) of 0.52, which are superior to MS specimens (1150°C-15 min) with P r = 21.1 μC/cm2, E c = 18.9 kV/cm and k t = 0.48, implying that PCCWT system appears to be more difficult to allocate a suitable processing condition using microwave sintering. Further discussion will be made in the context.