Dielectric properties of K-1-xLixTa1-yNb(y) O-3 crystals

The dielectric properties of K1-xLixTa1-yNbyO3 (KLTN) crystals as functions of the frequency, temperature and electric field are presented. The dielec tric measurement were conducted on several crystals with moderate Nb concen tration, 10%-40% and small Li concentration, <1%. In this article we presen t the results for two representative samples, one with 16% of Nh and 0.8% o f Li and the other with 36% of Nh and 0.6% of Li. The dielectric permitivity in the vicinity of the phase transition in the s ample with 16% of Nh increases when an electric field is applied. This incr ease is connected with the sign change from positive to negative of gamma, the coefficient of P-4 in the free energy function. This result suggests th at the phase transition in KLTN crystal is first order phase transition. A relaxation process with activation energy of 0.107eV and a high temperature frequency of 3x10(11)Hz was found. This relaxation process was attributed to Li 90 degrees flips.