Dielectric properties of triglycine sulphate crystals admixtured with D- and DL-phenylalanine

The paper reports studies on the effect of D-phenylalanine and DL-phenylala nine admixtures on dielectric properties and domain structure of triglycine sulphate crystals. Permittivity epsilon and loss tangent tg delta were mea sured in a wide range of temperatures (10-340 K) as a function of measuring field varied from 1 to 10000 kHz, for samples cut out from two growth pyra mids (001) and (110) from triglycine sulphate crystals containing different concentrations of admixtures. A comparison of the effects of D-phenylalani ne and DL-phenylalanine admixtures on dielectric properties of triglycine s ulphate crystals was made. With increasing concentrations of admixtures in the crystals, the values of epsilon(max) decreased while E-c and E-b (bias field) increased, and P-s and T-c showed insignificant changes. Observation s of the domain structure of the admixtured crystals by the liquid crystal method proved its refinement and irregularity. Changes in the domain struct ure of the crystals occurring in the process of spontaneous ageing were ana lysed.