Study On Preparation And Properties Of BaTiO₃Based Ferroelectric Ceramics

This paper reported that the xerogel of barium titanate was prepared with sol-gel technique, then the xerogel was stoved and the powder was received. After grinding, calcining and also gringding with the powder, and the barium titanate ceramics and lanthanum barium titanate ceramics were obtained. Microstructure of the ceramics of kinds of calcine temperature and sintering time were analyzed by XRD. SEM patterns represent the surface feature of the ceramics. Ferroelectric properties, dielectrical properties and piezoelectrical properties were studied by TF2000Analyzer. From XRD patterns, we can see the crystal of barium titanate ceramic is orthorhombic. There is a link-peak near the45degree with the increasing of the calcine temperature and sintering time, which proved the tetragonal phase appeard. The angle of diffraction moved to lower angle followed the calcine temperature increasing. The crystal size is uniform and about1micrometer, the crystal will grow with the increasing of the calcine temperature and sintering time. The maximum density of the ceramic is95%.The ferroelectric properties were measured by TF2000Analyzer. With the increasing of the calcine temperature, the surplus polarization increased and the coercive field decreased. It explained that the enhanced calcined temperature will obtain the switch domains. With the increasing of the voltage or frequence, the switching current increased, but the effect of the temperature is weak. That means voltage and frequence can improve the number of the domain and the reversal rate effectively.The dielectrical properties of the barium titanate ceramics were tested under room temperature and100Hz, the results make clear that with the increasing of the calcine temperature and sintering time, the dielectric constant rises, and the maximum dielectric constant is65792under sintering time4h and calcine temperature is1310℃On the one hand, due to the weak ferroelectric of the grain boundary, so the bigger size of the crystal received the smaller grain boundry. On the other hand, the space charge of grain boundary will hinder the polarization charge on the surface of the grain, and the space charge polarization emerged, and depletion layer will form and reduce the polarization. So the bigger the grain size and the smaller grain boundry, and dielectrical properties improved. The maximum dielectric tunability is97%with sintering time is4h and calcine temperature is1260℃.The piezoelectrical properties of barium titanate with sintering time is4h and calcine temperature is1310℃and the maximum piezoelectrical coefficient is333pm/V, which means if the ceramics were impacted by voltage, then the obvious deformation will be produced.Lanthanum barium titanate ceramics were prepared by sol-gel combining twice-sintering method and the crystal phase is orthorhombic. The grain size is300nm. The relative density of the crystal is92.5%. The surplus polarization and coercive field will reach the maximum when the addition is0.4%in this experiment. The maximum dielectric constant of0.2%-doped lanthanum barium titanate ceramic is18325with the calcine temperature of1310℃.