Electric field dependent microwave loss in BaTiO3 and KTaO3

The electric field dependent microwave loss of anharmonic pure BaTiO3 and KTaO3 ferroelectric crystals has been calculated in its paraelectric phase from the Silverman-Joseph Hamiltonian augmented with fourth order phonon coordinates using double time Green's functions. The loss tangent consists of a contribution, which is quadratic in applied biasing and is a field independent contribution. The variation of tan delta with applied Field is noticeable in the vicinity of Curie temperature. In the higher temperature region, the electric field effect ceases and the increase in loss arises mainly due to higher order anharmonic terms. In both cases (BaTiO3 and KTaO3) loss tangent increases with the increasing electric field.