Giant Dielectric Constant And High-Temperature Dielectric Relaxation Properties In La-Doped Srtio3 Ceramics

Sr1-3x/2LaxTiO3 (SLTO) ceramics (x = 0.05, 0.10, 0.15) were prepared with giant dielectric constant by the traditional solid-state method at 1350 degrees C. The temperature dependence of the dielectric constant was obtained at the temperature ranging from 29 degrees C to 500 degrees C and the frequency ranging from 2 kHz to 2 MHz. Two sets of relaxation peaks appear in the low temperature (region I) and the high temperature (region II), respectively. For region I, we conclude that the relaxation behavior is related to the oxygen vacancy migration. For region II, the two relaxation processes are caused by grain boundary for high frequency and Sr or Ti defects at grain interior for low frequency. With the doping amount reaching 0.15, the relaxation peaks disappear and become a common phase transition because of the aggravation of lattice distortion. These possible physical mechanisms of two sets of relaxation peaks are briefly discussed.