Investigations of the electrical property, diffuse reflectance and ESR spectra of the La-(Fe,Mn)-codoped PTCR BaTiO3 annealed in reducing atmosphere

摘要

Electrical properties of La-(Fe,Mn)-codopedpositive temperature coefficient of resistivity (PTCR) BaTiO3ceramics were studied by combining their diffuse reflectancemeasurements and electron spin resonance (ESR) spectroscopy.La-(Fe,Mn)-codoped samples showed high durability to reducingatmosphere. It is assumed that Fe and Mn ions segregated in thegrain boundary contribute to the density of surface acceptor states,meanwhile localizing electrons in a form of Ti3+ and stabilizing thechemisorbed oxygens through La3+-Mn3+,4+ or La3+-Fe3+ pairs. Inaddition, ESR signals of Fe3+ in annealed samples was intensifiedabove Curie temperature (Tc), indicating that Fe ions stillmaintained its high valence states (Fe3+) in the grain boundary evenafter annealing in reducing atmosphere.