Thermally-stimlated polarization / depolarization current (TSPC / DC) measurements were made on high-purity doped and undopod BaTiO3 as a function of applied field, heating rate, dopant level, and Ba:Ti ratio. The form of the TSPC/DC curves is dependent upon both the resistive and ferroelectric properties of BaTiO3. For TSPC spectra, current peaks are exhibited due to the change in in magnitude and direction of the spontaneous polarization with changing crystal structure. In particular, whether the phase transition is first or seoond order influsnaes the existence and magnitude of the current peaks. TSDC measurements are essentially dynamic pyroelectric measurements and as such are useful in determining the pyroeleotric coefficient and the magnitude of the spontaneous polarization. The TSDC current did not approach zero in the paraelectric region for some of the specimens, indicative of an anomalous polarization present due to the migration of charged oxygen vacancies. This information is Useful for analyzing DC electrical degradation. Variation in the Ba:Ti ratio affects the grain size distribution, and hence, the ease of domain switching. This directly affects the presenoe and magnitude of current peaks. The Ba:Ti ratio also affects the activation energy of conduotion, resistivity, and degradation behavior, all of which are reflected by the magnitude of the TSPC/DC current in the paraelectric region.
Available at: http://works.bepress.com/wayne-huebner/15/