An automated ferroelectric hysteresis loop tracer, developed using an INTEL 8085 microprocessor is described. This setup can be used to study the growth of a hysteresis curve at any desired temperature instantaneously after the application of a field. Since the setup allows the storage of data for each cycle of the applied field, this can be used to study the response of ferroelectric domains in an applied alternating field with time on unpoled or poled samples. The setup is interfaced with a personal computer to obtain directly the values of loop parameters.

An attempt has been made to identify the optimum parameters for good dielectric resonator materials. The dependence of dielectric constant of the system BaLn,TiaOlz (Ln=La, Pr, Nd, Sm) on packing fraction and nephelauxetic ratio is discussed. The reported dielectric data for this system were treated using the multiregression method.1968

The procedure for measuring ac conductivity at microwave frequencies is outlined. The Tc of typical 123 oxide superconductors obtained by ac measurement is lower than that obtained by dc measurement. Possible reasons for this observation are also considered.

The sharp increase in microwave power loss (the reverse of what has previously been reported) at the transition temperature in high-T, superconducting systems s u c h as YBaCu oxide (polycrystalline bulk and thin films obtained by the laser ablation technique) and BiPbSrCaCu oxide is reported. The differences between DC resistivity (p) and the microwave power loss (related to microwave surface resistance) are analysed from the data obtained by a simultaneous measurement set-up. The influence of various parameters, such as preparation conditions, thickness and aging of t h e sample and the probing frequency ( M 8 GHz), on the variation of microwave power loss with temperature is outlined.

A technique for the simultaneous measurement of the dc conductivity and microwave (ac) properties on the same sample is described. The difference in transition temperatures between dc and microwave frequencies (i) at -6.2 GHz (J-band), ~9 . 2 GHz (X-band), = 13.5 GHz (P-band), and = 17.8 GHz (P-band) on YBaCu oxide and (ii) at ~6 . 2 GHz on YBaCu oxide thin films and BiPbSrCaCu oxide has been evaluated. From the observations of these simultaneous measurements, the energy dependent variations of these simultaneous measurements, the energy dependent variation of AT, (T,(dc) -T,(ac)) and the nou-zero microwave power loss beyond the superconducting transition temperature are discussed.