Grain Boundaries of Semiconducting SrTiO₃ and BaTiO₃ Ceramics Synthesized from Surface‐Coated Powders

Abstract

The chemical and electrical features of the grain boundaries in polycrystalline SrTi 0.99 Nb 0.01 O 3 (ST) and BaTiO 3 (BT) ceramics, which were synthesized by hot-press sintering Na-and Mn-coated semiconducting ST and BT powders, respectively, were investigated. Because of the excess negative electric charges formed near grain boundaries, electrostatic potential barriers were formed near the grain boundaries. The electrical features of the grain boundaries in ceramics are very sensitive to the amount of the coating material. When the amount of the coating material was increased from 0 to 5 wt%, the threshold voltage of the ST ceramics and the resistivity jump ratio of the BT ceramics increased from 0.7 to 81.0 V/cm and from 1.0 to 2.0 ؋ 10 3 , respectively. The electrical features of the grain boundaries are related to their chemical characteristics.

Abnormal reoxidation effects in Ba‐excess La‐doped BaTiO3 ceramics prepared by the reduction‐reoxidation method

“…It is known that semiconducting BaTiO 3 ceramics were usually composed of grain bulks and grain boundaries. The resistances of grain ( R g ) and grain boundary ( R gb ) can be obtained from the intercepts in vs Z ′ plot at high and low frequencies . The changes of R g and R gb with oxidation temperature were shown inset.…”

The preferred CSL misorientation distribution in polycrystalline SrTiO3

“…Perovskite SrTiO 3 materials are widely used in electronic devices such as nonvolatile memory devices, large‐dielectric‐constant transparent insulators, varistors and sensors, because of their important electrical characteristics such as high‐permittivity, super conductivity at low temperature and sensitive environmentally dependent properties (Waser & Hagenbeck, 2000; Park & Cho, 2001; Reagor & Butko, 2005). These and other important physical properties of polycrystalline perovskite materials are often determined by the grain boundary structures (Waser & Hagenbeck, 2000; Park & Cho, 2001) such as whether they involve coincidence site lattices (CSL) or intergranular films (Ernst et al . 2001; Drake et al .…”

Phase Transition and Physical Characteristics of Nanograined BaTiO3 Ceramics Synthesized from Surface‐Coated Nanopowders

“…This seems to be related to the increase in the grain boundary electrostatic potential barrier of the former, compared with that of the latter. 3 In contrast, the resistivity of the ceramics at room temperature, which were prepared from the noncoated powders, is larger than that of the ceramics prepared from the powders coated with Mn, because the former contained the cubic and tetragonal phases at room temperature, while the latter contained only the tetragonal phase.…”

“…1 The electrical features of polycrystalline BaTiO 3 ceramics are known to be crucially determined by the structural and chemical characteristics of grain boundaries as well as the phase transition at operation temperature. [1][2][3] It has been reported that the physical properties of BaTiO 3 and PbTiO 3 powders are critically affected by their size. 4 -12 The size-related dielectric properties of the powders are ascribed to residual internal stress and crystalline imperfection.…”