IONIC-CONDUCTIVITY, FERROELECTRICITY AND CHEMICAL BONDING IN TKWB TYPE CERAMICS OF THE K6LI4TA10O30-PB5TA10O30 SYSTEM

Correlations between Curie temperature and chemical bonding were found in ferroelectric tetragonal potassium tungsten bronze type ceramics [ TKWB] using the extended Huckel tight-binding (EHTB) method. The influ ence of Pb for K,LI substitution is shown. AC complex impedance measur ements were performed on ceramics with compositions corresponding to P b5xK6(1-x)Li4(1-x)Ta10O30 (PKLT) in a wide temperature range. The cond uctivity relaxation parameters of Li+ conducting PKLT ceramics were de termined. 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 o f the results obtained from EHTB calculations.