The temperature dependence of the OH stretching mode in the incipient feroelectrics SrTiO 3 and KTaO 3

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Abstract
The OH infrared strectching mode near 3500 cm−1 has been observed in high resolution as a function of temperature in the perovskytes SrTiO3 and KTaO3. In SrTiO3 above the phase transition temperature of 110 K and in KTaO3 over the whole range of temperature studied, we have observed a principal absorption peak accopanied by three satellites. Additional peaks appear in the case of SrTiO3 below 110 K. We interpret their presence and their temperature dependence as being relate to the combined effect of fluctuations of the ferroelectric soft mode and the antiferrodistorsive phase transition which interact with the OH bond.