MICROWAVE LOSSES IN INCIPIENT FERROELECTRICS AS FUNCTIONS OF THE TEMPERATURE AND THE BIASING FIELD

The dielectric constant of ferroelectric materials can be controlled b y an applied electric field. That is promising for applications using the microwave technique. The widespread use of ferroelectric materials at microwaves is retarded by a considerable high dielectric loss by t he materials at high frequencies. The goal of this article is to model the essential mechanisms of losses in incipient ferroelectrics at mic rowave frequencies. The following materials are studied: strontium tit anate (SrTiO3) and potassium tantalate (KTaO3). The following loss mec hanisms are considered: fundamental loss determined by multiphonon sca ttering of the soft ferroelectric mode and transformation of microwave electric field oscillations into acoustic oscillations due to residua l ferroelectric polarization. (C) 1998 American Institute of Physics. [S0021-8979(98)00614-8].