Abstract
We present experimental results of dielectric and birefringence measurements on 3.5% and 8% Li∶KTaO3 as a function of temperature. These results indicate that the 8% Li∶KTaO3 sample undergoes a ferroelectric phase transition at 97 K. The 3.5% sample seems to undergo a distortive transition at ∼75 K. Raman experiments show that the splitting of the TO1 mode of the 8% Li sample extrapolates to zero at ∼97 K supporting the conclusion that this sample undergoes a phase transition at this temperature. Raman spectra of both samples at temperatures above the phase transition or freezing temperatures exhibit in addition to second order Raman features first order Raman lines. These lines have the properties of fluctuation induced first order Raman scattering. Measurement of the integrated intensity of these lines is used to obtain the temperature dependence of the fluctuation intensity. The results are compared to the Halperin and Varma theory. The data obtained for the 3.5% Li sample partialy fits the theory. However the results for the 8% Li sample do not fit the theory. The misfit is attributed to the overlap of defect zones.
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