GLASSY AND FERROELECTRIC ASPECTS OF POTASSIUM TANTALATE NIOBATE

The dielectric susceptibility obtained for a crystal of KTaO0.96Nb0.04O3 is presented as a function of temperature and frequency. The data are analysed in terms of parameters describing the relaxation strength and the width of the relaxation time distribution around an average value. The results are compared with those reported for KTa1-xNbxO3 Crystals with lower niobium concentration (x = 0, 0.0075 and 0.02). The degree of disorder introduced by niobium is thus described as function of niobium concentration. It is shown that the phase transition in KTaO0.96Nb0.04O3 cannot be interpreted by the usual ferroelectric picture, nor by the glass-like behaviour.