Electric field dependent microwave loss in BaTiO3 and KTaO3

The electric field dependent microwave loss of anharmonic pure BaTiO3 and K TaO3 ferroelectric crystals has been calculated in its paraelectric phase f rom the Silverman-Joseph Hamiltonian augmented with fourth order phonon coo rdinates using double time Green's functions. The loss tangent consists of a contribution, which is quadratic in applied biasing and is a field indepe ndent contribution. The variation of tan delta with applied Field is notice able in the vicinity of Curie temperature. In the higher temperature region , the electric field effect ceases and the increase in loss arises mainly d ue to higher order anharmonic terms. In both cases (BaTiO3 and KTaO3) loss tangent increases with the increasing electric field.