Horia V. ALEXANDRU1*, Marinel DAN2, Constantin-Paul GANEA3
Abstract. Triglycine sulphate crystal (TGS) is a hybrid organic-inorganic ferroelectric crystal with a large electronic band-gap, transparent in visible spectra. It has large applications in electronics, as thermal IR detector. Pure and doped TGS crystals of 3-5 cm linear dimensions
were grown at constant temperature in the paraelectric phase (52 oC), by slow solvent evaporation. Pure TGS samples show non-reproducible values of permittivity and losses in the ferroelectric phase after the “excursion” in the paraelectric phase. Walking up and down the
crystal temperature, using a special program, the permitivity and losses were automatically recorded and analyzed. There is a continuous decrease of permittivity towards an equilibrium value during a long period of time. Previous AFM measurements from the literature have
revealed peculiar aspects of domain dynamics. The relaxation process of permittivity was considered according to the equation r = A – B exp(-t/). However, surprisingly, there is not a unique relaxation time . For the first 500 sec (or so), the relaxation time is 7 minutes, while between the next time decades 1.000 – 10.000 – 100.000 sec, it is approximately 1 hour and 8 h respectively. The process is related with the ferroelectric domain’s dynamics, which are more or less strongly pined by dislocations or some other lattice defects.
Keywords: Perovskite; First-principles calculations; Electronic properties; Elastic properties
DOI 10.56082/annalsarsciphyschem.2021.1.29
1 Prof. Dr. Horia ALEXANDRU, Faculty of Fhisics, University of Bucharest,
*Academy of Romanian Scientists, ROMANIA.
2 Marinel DAN, cand Dr. Degre, Faculty of Fhisics, University of Bucharest.
3 Dr . Constantin-Paul GANEA, National Institute of Materils Physics, Bucharest Magurele, ROMANIA
PUBLISHED in Annals of the Academy of Romanian Scientists Series on Physics and Chemistry, Volume 6, No1