F-centers mechanism of long-term relaxation in lead zirconate-titanate based piezoelectric ceramics. 2. After-field relaxation

Abstract

The paper presents results of experimental study of the dielectric constant relaxation during aging process in Pb(Zr,Ti)O 3 based solid solutions (PZT) after action of external DC electric field. The said process is a long-term one and is described by the logarithmic function of time. Reversible and nonreversible relaxation process takes place depending on the field intensity. The relaxation rate depends on the field strength also, and the said dependence has nonlinear and nonmonotonic form, if external field leads to domain disordering. The oxygen vacancies-based model for description of the long-term relaxation processes is suggested. The model takes into account the oxygen vacancies on the sample's surface ends, their conversion into F þ -and F 0 -centers under external effects and subsequent relaxation of these centers into the simple oxygen vacancies after the action termination. F-centers formation leads to the violation of the original sample's electroneutrality, and generate intrinsic DC electric field into the sample. Relaxation of F-centers is accompanied by the reduction of the electric field, induced by them, and relaxation of the dielectric constant, as consequent effect.

Ab initio hybrid DFT calculations of BaTiO3 bulk and BaO-terminated (001) surface F-centers

“…Oxygen vacancy (V 0 ) usually traps two electrons (so-called neutral F -center). Theoretical [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] and experimental investigations [28][29][30][31][32][33] of F -centers in ABO 3 perovskites are very hot topic, since the F -center is the most known, classical point defect in ABO 3 perovskites, which considerably affects all material properties. It is surprising that despite the large technological potential of BaTiO 3 , the bulk F -center defects in BaTiO 3 perovskite is not sufficiently well studied, and, to the best of our knowledge, ab initio calculations dealing with BaO-terminated BaTiO 3 (001) surface F -centers have not yet been performed.…”