Core‐Shell Structures in ZrO₂‐Modified BaTiO₃ Ceramic

Abstract

Pure BaTi03 exhibits a paraelectric-to-ferroelectric phase transition at 130°C. When stoichiometric BaTi03 is combined with 10 mol% Zr02, the relative permittivity (E,) changes to a broad, relatively insignificant temperature dependence, and the Curie point, Tc, is not sharply defined. However, the transition sharpens at T = 95°C when these samples are sintered for a longer period of 60 h. SEM, EDAX analysis coupled with TEM observation gives three types of core-shell structures of different microstructural characteristics which are related to the diffuse phase transition. Chemical inhomogeneity, due to Zr4+ distribution in the core-shell structure, is proposed to account for the diffuse phase transition behavior. [

Mesocrystals—Ordered Nanoparticle Superstructures

“…The whole coarse grains behave like a single crystal with small misorientation. The formation of coarse grains with a core-shell structure in KNN-based ceramics is different from the core-shell grain structure in BaTiO 3 -based ceramics, [92][93][94] which results from the concentration gradients of additives. A transformation of the nano-building-block to a typical core-shell grain structure similar to mesocrystal formation via self-assembly was observed both in pure KNN and LKNNT systems.…”

Effects of core/shell volumetric ratio on the dielectric-temperature behavior of BaTiO3

“…When a core/shell structure forms, the dielectric-temperature behavior of the sample is typically improved, showing insensitive variation of the dielectric properties in a wide temperature range while also satisfying industrial standards [8][9][10]. Because of its positive effect on dielectric behavior, the core/shell structure of BaTiO 3 has won attention from many researchers [2][3][4][5][6]. The improvement of the temperature-dependent behavior has been attributed to the contribution of the shell phase, which shows an appreciable displacement of the maximum dielectric constant down below room  temperature with a broadened transition peak, so-called diffuse phase transition (DPT) behavior, similar to that of relaxor materials [11][12][13][14].…”

“…The effects of various kinds and amounts of additives have been studied [2,4,5,9,10,[15][16][17][18][19][20][21][22], including in particular those of rare earth elements with intermediate ionic radii (Dy, Ho, Y and Er) [9,10,[19][20][21][22][23]. In the case of rare earth doping, high insulation resistance can be maintained for a long time, which enables the realization of thinner dielectric layers and extended life time in the use of MLCCs [24].…”

“…The addition of solute elements often results in the formation of an inhomogeneous microstructure during sintering that is typified by a core/shell structure [1][2][3][4][5][6][7]. A core/shell grain is a dual-phase grain that consists of a core phase at the center and a shell phase around the core.…”

Design of a bilayer ceramic capacitor with low temperature coefficient of capacitance

“…[5][6][7][8][9][10] Limited diffusion of the dopants into BT grains leads to a concentration gradient of doped BT resulting in a "core-shell-like structure" (CS). 5,6,[11][12][13][14][15] This structure can be considered to be a core-region of undoped BT (Tc $ 120-130 C) surrounded by a shell-region of micro volumes of different dopant concentrations, leading to a spread of Curie temperatures. 12 This approach engineers CS microstructures with a broad permittivity-temperature profile, reducing TCC to the levels required for industry standard ratings.…”