The contributions to the curie-weiss dependent dielectric loss-tangent in paraelectrics

From the lattice dynamics of the paraelectric crystal possible dielectric loss processes are considered, in particular those which may lead to a Curie-Weiss temperature dependence of the loss tangent. It is shown that conversion between optical and acoustic phonon modes cannot give rise to the frequency dependence which is observed experimentally at low frequencies. It is proposed that the conversion to low frequency local modes, arising at grain boundaries or from lattice disorder, rather than to acoustic modes may account for the observed temperature and frequency dependence.