High-temperature charge carrier transportation behavior of Zn doped perovskite-like La2Ti2O7 ceramics

Abstract

La₂Ti₂O₇ ceramic has a perovskite-like structure with super-high Cuire temperature (T_c ~ 1460 ℃), which is an excellent candidate for the application as a high-temperature accelerator sensor used at beyond 1000 ℃. The high temperature electrical conductivity resulting from charge carrier transport has a major influence on the sensitivity of sensors. Here, Zn was introduced as an acceptor into La₂Ti₂O₇ ceramics for high-temperature electrical properties. All the samples show pure perovskite-like structure with P2₁ space group and compact microstructure. With the introduction of Zn up to x = 0.08, the insulation resistance of the ceramics was enhanced more than 1000 times. Impedance spectroscopy and modulus spectroscopy were used to investigate the high-temperature transport of charged carrier. Interestingly, the acceptor doping resulted in an increasing concentration of oxygen vacancies, but a significant increase in both electrical insulation and activation energy of the ceramics was observed. The thermal activation mechanism is responsible for the high-temperature charge carrier transport. It is suggested that although the concentration of oxygen vacancies increase, Zn doping depresses the motion of oxygen vacancies in perovskite-like structure. The results provide a method to improve the insultation of high-temperature piezoelectric ceramics.