Effects of Sintering Conditions on Giant Dielectric and Nonlinear Current-Voltage Properties of TiO 2 -Excessive Na 1/2 Y 1/2 Cu 3 Ti 4.1 O 12 Ceramics.

The effects of the sintering conditions on the phase compositions, microstructure, electrical properties, and dielectric responses of TiO 2 -excessive Na 1/2 Y 1/2 Cu 3 Ti 4.1 O 12 ceramics prepared by a solid-state reaction method were investigated. A pure phase of the Na 1/2 Y 1/2 Cu 3 Ti 4.1 O 12 ceramic was achieved in all sintered ceramics. The mean grain size slightly increased with increasing sintering time (from 1 to 15 h after sintering at 1070 °C) and sintering temperature from 1070 to 1090 °C for 5 h. The primary elements were dispersed in the microstructure. Low dielectric loss tangents (tan δ~0.018-0.022) were obtained. Moreover, the dielectric constant increased from ε'~5396 to 25,565 upon changing the sintering conditions. The lowest tan δ of 0.009 at 1 kHz was obtained. The electrical responses of the semiconducting grain and insulating grain boundary were studied using impedance and admittance spectroscopies. The breakdown voltage and nonlinear coefficient decreased significantly as the sintering temperature and time increased. The presence of Cu + , Cu 3+ , and Ti 3+ was examined using X-ray photoelectron spectroscopy, confirming the formation of semiconducting grains. The dielectric and electrical properties were described using Maxwell-Wagner relaxation, based on the internal barrier layer capacitor model.