Grain Boundary Engineering and Positive Temperature Coefficient of Resistance Behavior in La3+-Doped LiTaO3 Lead-Free Ceramics

In this study, to our knowledge, this is the first systematic demonstration of a room-temperature to 200 °C PTCR window in La-doped LiTaO 3 with grain-boundary-dominated barriers. The results show that the solubility of La in LiTaO 3 was less than 15wt.%, and the La contents would affect the microstructure as well the electrical conductivity of LiTaO 3 . For the LiTaO 3 -based materials with/without La doping, the materials exhibit the PTCR jump (log (R max / R min )) of 2.6∼3.6 between room temperature and ∼200 °C, and varied with La contents. By combining impedance spectroscopy and time relaxation techniques, the complex impedance response of LiTaO 3 -based ceramic materials was analyzed, revealing multiple grain boundary resistances corresponding to relaxation processes with distinct time constants (τ) were the origin of the PTC effect.