High Schottky barrier at grain boundaries observed in Na_1/2Sm_1/2Cu₃Ti₄O₁₂ ceramics

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• 作者：Weeraya Somphan ; Prasit Thongbai ; Teerapon Yamwong ; Santi Maensiri
• 关键词：A. Ceramics ; C. Impedance spectroscopy ; C. Photoelectron spectroscopy ; D. Dielectric properties ; D. Electrical properties
• 刊名：Materials Research Bulletin
• 出版年：2013
• 出版时间：October, 2013
• 年：2013
• 卷：48
• 期：10
• 页码：4087-4092
• 全文大小：1682 K

文摘

The dielectric properties and nonlinear current-voltage characteristics of Na_1/2Sm_1/2Cu₃Ti₄O₁₂ ceramics prepared by a conventional solid state reaction method were investigated. Na_1/2Sm_1/2Cu₃Ti₄O₁₂ ceramics exhibited a high dielectric permittivity of 7.0-8.4 ¡Á 10³ and low loss tangent (tan ¦Ä¡«0.030-0.041). Non-Ohmic properties with a high breakdown voltage of ¡«2208 V cm^?1 and large nonlinear coefficient of 15.6 were observed in Na_1/2Sm_1/2Cu₃Ti₄O₁₂ ceramics. Using complex impedance analysis, Na_1/2Sm_1/2Cu₃Ti₄O₁₂ ceramics were shown to be electrically heterogeneous consisting of semiconducting grains and insulating grain boundaries. Giant dielectric properties were described based on the electrically heterogeneous microstructure. X-ray photoelectron spectroscopy analysis suggested that the semiconductive nature of grains may be related to the presence of Cu⁺ and Ti³⁺. The formation of an electrostatic potential barrier at the grain boundaries of Na_1/2Sm_1/2Cu₃Ti₄O₁₂ ceramics was suggested to be caused by the Schottky effect. Interestingly, high electrostatic potential barriers at grain boundaries in Na_1/2Sm_1/2Cu₃Ti₄O₁₂ ceramics were calculated and found to be 0.925-0.964 eV.