Oxidation-induced strain relaxation and related dielectric-temperature behavior in core/shell grained BaTiO3

Abstract

The effect of oxidation on dielectric-temperature behavior of core/shell grained BaTiO 3 was studied in an attempt to reveal the prime governing parameter of dielectrictemperature behavior. BaTiO 3 samples doped with 3 mol% Y 2 O 3 or 3 mol% Dy 2 O 3 with the same effective charges were sintered in a reducing atmosphere (Po 2 <10 −13 ) and oxidized at 1050-1250°C for 10 h in air. In the Y-doped samples, as the oxidation temperature increased, the fraction of the grains with ferroelectric domains in the shell increased from 18 to 54 % and the residual strain decreased. With an increased domain fraction, the dielectric-temperature behavior became poor, and a dielectric peak appeared. On the other hand, all the Dy-doped and air-annealed samples exhibited relatively high fractions of grains with ferroelectric domains in the shell, 32 % at 1050°C and 63 % at 1250°C, indicating a considerable reduction of residual strain in all the samples. The temperature stability of the Dy-doped samples was poor, and there was a dielectric peak, irrespective of the oxidation temperature. This difference in dielectric response between the Ydoped and Dy-doped samples reveals that the prime factor governing the dielectric-temperature stability is the residual strain in the core/shell grains rather than the previously suggested factors of defect concentration, dopant concentration in the shell and the occupational sites of rare-earth dopants.

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.…”