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Abstract
The temperature evolution of TO1 Raman spectra was investigated in single crystals of K1−xLixTa1−yNbyO3:Cu with different Li and Nb amounts. Auxiliary observations of TO4 spectra were also performed. In a sample with x = 0·002 and y = 0·025 and containing 190 ppm of Cu, the results indicate a clear-cut transition to an ordered phase around 55 K, in good agreement with previous findings from dielectric measurements in the same crystal. However, no evidence was found of a role of Cu in this structural modification. Samples with x = 0·01 and y = 0·003 revealed features of an order-disorder phase transition around 45 K, irrespective of the presence of Cu.