Structure And Properties Of PLZT And YIG Ceramics Prepared By Spark Plasma Sintering

As a rapid and low temperature sintering technology, spark plasma sintering (SPS) has been attracting more and more interest in recent years. SPS has been widely used to modify microstructure of various materials. In this work, SPS was used to prepare Pb0.92La0.08(Zr0.52Ti0.48)03(PLZT) and Y3Fe5O12(YIG) ceramics and their microstructures and properties were investigated. The following conclusions were obtained.PLZT ceramics with higher density, smaller grain size and smaller domain were prepared by SPS. The c/a value of the sample prepared by SPS is1.008, which is very close to1. As a result, the PLZT ceramics prepared by SPS have smaller dielectric constants, slightly high Curie temperatures, smaller saturated polarizations, smaller remanent polarizations, and slightly higher coercive fields. Meanwhile, PLZT ceramics possess higher breakdown strengths and higher energy storage densities, the biggest energy storage density can reach0.727J/cm3.Three dielectric relaxations of YIG ceramics are identified in the temperature range from133K to620K. The low temperature dielectric relaxation is caused by the charge carrier hopping between the Fe2+-Fe3+. The medium temperature dielectric relaxation most likely arises from the inhomogeneous structure, such as grain boundaries (interface Maxwell-Wagner polarization effect). The high temperature dielectric relaxation can be attributed to the conduction. However, only the low temperature and the high temperature dielectric relaxation were observed in the YIG ceramics prepared by SPS. The activation energy of the hopping process becomes smaller, and the medium temperature dielectric relaxation related to the Maxwell-Wagner polarization effect becomes weak.It was found that Bi3+substitution significantly decreases the dielectric response of YIG ceramics due to the decrease of the concentration of Fe2+and the conductivity. Bi substitution decreases the activation energy of the electron hopping between Fe2+and Fe3+, which leads to decrease of the characteristic temperature of the low temperature dielectric relaxation. The decrease of conductivity in Bi-substituted YIG ceramics leads to the weakening of the high temperature (associated with conduction) dielectric response. The vacuum during SPS may improve the concentration of Fe2+, and then enhances the low temperature dielectric relaxation. On the other hand, the variation of the conductivity of the grain gives rise to the change of the inhomogeneous structure, which leads to weakening of the middle temperature (associated with the inhomogeneous structure) dielectric relaxation.