Department of Physics, H N B Garhwal Central University, Campus Pauri, Pauri (Garhwal), Uttarakhand, India 246001.
*E-mail:-dushyantyradeep@yahoo.co.in
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The dependence of microwave loss of anharmonic mixed Ba1_xCaxTi03 perovskites on electric field has been calculated in its paraelectric phase from the Silverman-Joseph Hamiltonian augmented with fourth order phonon coordinates using double times Green's function. The results are used to obtain an expression for the frequency and temperature dependence of dielectric loss at microwave frequencies due to impurity and anharmonic scattering in presence of external electric field. The loss tangent consists of a contribution which is quadratic in applied biasing plus a field independent term. The variation of loss tangent 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.
Green's function, Hamiltonian, Microwave losses, Anharmonicity, Perovskites
