Ionic conductivity, ferroelectricity and chemical bonding in TKWB type ceramics of the K6Li4Ta10O30-Pb5Ta10O30 system

Abstract

Correlations between Curie temperature and chemical bonding were found in ferroelectric tetragonal potassium tungsten bronze type ceramics [TKWB] using the extended Hckel tight-binding (EHTB) method. The influence of Pb for K,Li substitution is shown. AC complex impedance measurements were performed on ceramics with compositions corresponding to Pb _5x K _6(1–x) Li _4(1–x) Ta ₁₀ O ₃₀ (PKLT) in a wide temperature range. The conductivity relaxation parameters of Li ⁺ conducting PKLT ceramics were determined. Transport properties in these materials appear to be due to a Li ⁺ ion hopping mechanism. The influence of the substitution 6K ⁺ +4Li ⁺ →5Pb ²⁺ on the mobility is discussed with the assistance of the results obtained from EHTB calculations.