Non-Ohmic Properties and Electrical Responses of Grains and Grain Boundaries of Na<sub>1/2sub>Y<sub>1/2sub>Cu<sub>3sub>Ti<sub>4sub>O<sub>12sub> Ceramics

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• 作者：Jutapol Jumpatam ; Weeraya Somphan ; Jakkree Boonlakhorn ; Bundit Putasaeng ; Pinit Kidkhunthod ; Prasit Thongbai and Santi Maensiri
• 刊名：Journal of the American Ceramic Society
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：100
• 期：1
• 页码：157-166
• 全文大小：1921K
• ISSN：1551-2916

文摘

The dielectric and non-Ohmic properties of Na<sub>1/2sub>Y<sub>1/2sub>Cu<sub>3sub>Ti<sub>4sub>O<sub>12sub> ceramics sintered under various conditions to obtain different microstructures were investigated. Microstructure analysis confirmed the presence of Na, Y, Cu, Ti, and O and these elements were well dispersed in the microstructure. Na<sub>1/2sub>Y<sub>1/2sub>Cu<sub>3sub>Ti<sub>4sub>O<sub>12sub> ceramics exhibited non-Ohmic characteristics with large nonlinear coefficients of about 5.7&ndash;6.6 irrespectively of sintering conditions. The breakdown electric field of fine-grained ceramic with the mean grain size of &asymp;1.7 μm (&asymp;5600 V/cm) was much larger than those of the course-grained ceramics with grain sizes of &asymp;9.5&ndash;10.4 μm (&asymp;1850&ndash;2180 V/cm). Through optimization of sintering conditions, a low loss tangent of about 0.03 and very high dielectric permittivities of 18 000&ndash;23 000 with good temperature stability were successfully accomplished. The electrical responses of the grains and grain boundaries can, respectively, be well described using admittance and impedance spectroscopy analyses based on the brickwork layer model. A possible mechanism for the origin of semiconducting grains is discussed. The colossal dielectric response was reasonably described as closely correlated with the electrically heterogeneous microstructure by means of strong interfacial polarization at the insulating grain-boundary layers. The non-Ohmic properties of Na<sub>1/2sub>Y<sub>1/2sub>Cu<sub>3sub>Ti<sub>4sub>O<sub>12sub> ceramics were primarily related to their microstructure, i.e., grain size and volume fraction of grain boundaries.