Scaling of low-temperature conductivity spectra of BaSn1-xNbxO3 (x ≤ 0.100): Temperature and compositional-independent conductivity

We report our investigation on the low temperature scaling behavior of niobium-doped barium stannate. Electrical properties of the system BaSn1-xNbxO3 (with x = 0.001, 0.005, 0.010, 0.050, and 0.100), prepared by the solid-state route, were studied employing impedance spectroscopy in the temperature range 123-273 K and frequency range 10(-2) Hz to 3 MHz. Conductivity spectra for all the compositions were found to follow Jonscher's power law, sigma' = sigma(dc)[1 + (nu/nu(H))(p)]. We found that the hopping frequency nu(H), obtained from fitting this equation to the conductivity spectra, can be used as a scaling factor. All the compositions follow the time-temperature-superposition principle, with nu(H) as the scaling frequency. Moreover, the conductivity spectra of compositions with x <= 0.010 and with 0.010 < x <= 0.100 were separately found to show compositional scaling behavior with respect to the hopping frequency nu(H). This system showed a change in the charge compensation mechanism from electronic to ionic in its temperature dependence of the dc conductivity as the concentration changed from x = 0.010 to x = 0.050. The shape of the conductivity spectra also changed as the concentration changes from x = 0.010 to x = 0.050. We conclude that in this system, when the conduction mechanism does not change, nu(H) can be used as a universal scaling parameter.