SMALL POLARON INTERPRETATION OF BATIO3 TRANSPORT PROPERTIES FROM DRIFT MOBILITY MEASUREMENTS

The drift mobility mu d of melt-grown BaTiO3 single crystals has been determined in the 20 degrees C to 80 degrees C temperature range, using the Spear method. At room temperature, mu d=(3+or-1) *10-7 m2 V-1 s-1 with a resistivity of 4*108 Omega m. The mobility thermally activated with an activation energy of 0.15+or-0.04 eV. The results are interpreted in terms of non-adiabatic small-polaron hopping theory in the semi-classical and quantum mechanical cases. The related polaron and band parameters are deduced; taking into account the LO phonon energy h(cross) omega 0, the half-bandwidth J lies between 0.03 and 0.06 eV. Hall mobility, Seebeck coefficient and absorption coefficient are obtained as functions of parameters h(cross) omega 0, Ea and J and compared with existing experimental data.