INFLUENCE OF PROCESSING AND MICROSTRUCTURE ON DIELECTRIC PROPERTIES OF CALCIUM COPPER TITANATE CERAMICS

摘要

Solid-state processing techniques at relatively low calcination temperatures (850 °C) to prepare phase pure CaCu3Ti4O_(12), which will enable effective mitigation of dielectric losses is described. Microstructure observations by scanning electron microscopy (SEM) and density measurements show relatively homogeneous microstructure with the highest density at the sintering temperature of 1060 °C for 5 h. Impedence and dielectric properties are studied by impedance spectroscopy in the range of frequencies from 1 Hz to 2 MHz between room temperature (RT) and 200 °C with the applied 100mV AC. Impedence spectra dominated by ' resistance of grain boundary (Rgb), which is observed at low frequency is decreased from 8731 kΩ to 5 kQ when, the temperature is increased from RT to 200 °C. Dielectric constant remains constant over a wide frequency ranges from 10~4 to 10~5 Hz with low loss tangent of <0.1 in the measured temperature range (RT - 200 °C). The lowest observed tan 6 is 0.0266 at 80 °C at ~10 kHz with the dielectric constant of 5026. Further study is required to study contributions by grain, grain boundary, and electrode effects on the measured electrical properties.