Acceptor-donor concentration dependent polaronic relaxation, pinned electron defect dipole characteristic and colossal permittivity in co-doped rutile (Zn1/3Nb2/3)xTi(1-x)O2 (x = 0.02, 0.04, 0.06 and 0,08) ceramics

Abstract

Colossal permittivity with low loss tangent has been achieved by co-substitution of Zn and Nb in TiO2. Incorporation of the divalent and pentavalent ions has been confirmed by structural and Raman spectroscopic analysis. Specific ratio of acceptor-donor pairs led to observation of colossal permittivity (∼104) with a low loss tangent (<0.1). Evidence of localized donor electrons in the dielectric response shows the generation of electron pinned defect dipoles. Low-temperature dielectric relaxation has been observed which correspond to the polaronic conduction following Arrhenius law. As the acceptor-donor content increases, the polaronic relaxation dynamics occurs at higher temperatures. This also reveals that the defect complexes are strongly correlated. Permittivity values corresponding to the loss tangent minima have been compared as a function of acceptor-donor content. Finally, optimum sintering temperature, frequency, measurement temperature, and composition have been identified.