Research On Microstructure And Properties Of BaTiO₃ Piezo-ceramic Prepared By SPS

In this paper, BaTiO₃ piezoceramic was prepared by Spark Plasma Sintering (SPS) under different processing conditions using submicron cubic BaTiO3 powder as raw material.Firstly, the decarburization process was conducted by taking the sample sintered at 1150℃as example, of which the result indicates that after being held at 800℃for 2 hours, the carbon pollution in the SPS-sintered body can be completely removed, whereas, the BaTiO3 ceramic exhibits a high density and homogeneous microstructure.Furthermore, the effects of sintering temperature, holding time and heating rate on microstructures were investigated respectively. It was found that sintering temperature and holding time are the main processing parameters in influencing the microstructures of samples; heating rate take second place, whereas the change of sintering pressure only makes little effect on microstructures of samples.According to X-ray, EDS and SEM results, all the samples prepared by SPS are pure tetragonal lattice without second phase and other components. The grain sizes are between 3 and 10 micron. TEM result of sintered ceramics demonstrates a compact and homogeneous microstructure. The grain boundaries are clean and straight without impurities.The room temperature dielectric properties of samples are better than those prepared by conventional sintering method. Due to the dielectric and piezoelectric properties of samples depend on the grain size strongly, as well as by using SPS technique the grain size of the sintered body can be controlled by changing the parameters including sintering temperature, holding time, sintering pressure and so on, therefore SPS provides a method to conveniently adjust the dielectric and piezoelectric behaviors of materials through grain sizes controlling.Testing of Breakdown voltages and piezoelectric coefficients indicates that even a small amount of free carbon in the sintered body can deteriorate the piezoelectric property. It was recommended that use BN paste as die filler instead of carbon paper.Compared to conventional sintering method, SPS can greatly reduce sintering time and sintering temperature in preparing dense and homogeneous materials, and especially provide better dielectric properties than those conventionally sintered in the same grain sizes. The mechanism of SPS process has been revealed that pulse electric/magnetic effect and sparking plasma are main causes for accelerating diffusion, promoting matter migration, decreasing sintering temperature and promoting sintering.