Study of proper and improper microwave dielectric losses by means of teraherz and infrared spectroscopy

Title: Study ol"proper and improper microwave dielectric tosses by means of tcrahcrz and infrared speetroseopy Author: Ondfej Tkac Department: Department of Dielectrics. Institute of Physics, Academy of Sciences of C/ech Republic Supervisor: RNDr. Slanislav Kamba.C'Sc.. Na Slovance 2. Prague 8 Supervisor's e-mail adress: kambawT/u.c/ Abstract: In the llrst part of this thesis there is described relevant theory, especially we pay our attention to the principles of infrared speetroseopy and fitting models, then to the explanation of the terms proper and improper dielectric losses and we also discuss dielectrics and ferroelectrics. By means of Fourier transform infrared speetroseopy we measured infrared spectra at room temperature in the range of 30 - 3000 em"1. We lilted the spectra and then we extrapolated the final complex permit!vity into the microwave range. This enabled us to estimate the proportion of improper dielectric losses on total microwave losses. By the ceramic SiVxPlxCeVfinO-^ (.\0 to 9) we studied the impact of amount of lead on dielectric properties. We found out that the substitution of strontium with lead causes the increase of permitivity up lo several thousands and forces ferroelectric transition for x>2. With perovskitc Ca/n, jNb^ :,-xVx(.)1 (.v=0 to 0,01) we examined the inlluence of..