Defect structure and electrical properties of magnesium-substituted strontium titanate

Abstract

Attempts were made to synthesize samples in the system SrTi1-xMgxO3 forx = 0.01, 0.05, 0.10, 0.15, 0.20, and 0.25. Solid solution is obtained in the compositions withx γ{baby} 0.10. The structure remains cubic. Chemical analysis indicates oxygen deficiency in these materials. Initial substitution of Mg2+ ions (i.e., forx = 0.01) lowers the resistivity by several orders of magnitude. The activation energy,Ea, is very small and AC conductivity is independent of frequency in this composition. At higher concentration of Mg2+ ions (i.e., forx = 0.05 and 0.10), the resistivity and the activation energy again increases. AC conductivity,σAC, varies asωs wheres lies in the range 0.4-0.6, indicating conduction by hopping of charge carriers. The dielectric constant of these samples remains constant up to a particular temperature,Tc, beyond which it varies asA(T - Tc)/ωs′. The electrical behavior has been explained on the basis of the defect structure of these materials. © 1988 Academic Press, Inc. All rights reserved.