Abstract
Specific heat data are reported for KTa1-xNbxO3 mixed crystals with x=0.02, 0.03 and 0.09. The absolute value of the Nb concentration was determined by X-ray energy dispersive spectrometry. At the transition temperature Tc defined by the peak dielectric constant and the onset of spontaneous birefringence, no anomaly associated with Tc is detected in the specific heat. It is suggested that this result provides additional evidence for a diffuse phase transition in quantum ferroelectric KTa1-xNbxO3. Moreover, for x=0.09, a linear term in the temperature dependence of the specific heat is found below 3 K, in agreement with the general picture of glasslike properties displayed at low temperatures by numerous ferroelectrics.