Microstructure and electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics
- Department of Physics, Shandong University, Jinan 250100 (China) and State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)
CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics are prepared by the conventional solid-state reaction method under various sintering temperatures from 1000 to 1120 deg. C at an interval of 10 deg. C. Microstructures and crystalline structures are examined by scanning electronic microscopy and x-ray diffraction, respectively. Dielectric properties and complex impedances are investigated within the frequency range of 40 Hz-110 MHz over the temperature region from room temperature to 350 deg. C. It has been disclosed that the microstructures can be categorized into three different types: type A (with the small but uniform grain sizes), type B (with the bimodal distribution of grain sizes) and type C (with the large and uniform grain sizes), respectively. The largeness of low-frequency dielectric permittivity at room temperature is closely related to the microstructure. Ceramics with different types of microstructures show the diverse temperature-dependent behaviors of electrical properties. However, the existence of some common characteristics is also found among them. For all of the ceramics, a Debye-type relaxation emerges in the frequency range of 100 Hz-100 kHz at high measuring temperatures, which has the larger dielectric dispersion strength than the one known in the frequency range above 100 kHz. Thus, the high-temperature dielectric dispersion exhibits a large low-frequency response and two Debye-type relaxations. Furthermore, all of the ceramics show three semicircles in the complex impedance plane. These semicircles are considered to represent individually different electrical mechanisms, among which the one in the low-frequency range arises most probably from the contribution of the domain boundaries, and the other two are ascribed to the contributions of the domains and the grain boundaries, respectively.
- OSTI ID:
- 20788092
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 99; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCIUM COMPOUNDS
CERAMICS
COPPER COMPOUNDS
CRYSTAL STRUCTURE
DIELECTRIC MATERIALS
ELECTRIC IMPEDANCE
GRAIN BOUNDARIES
GRAIN SIZE
KHZ RANGE 01-100
KHZ RANGE 100-1000
MHZ RANGE 01-100
PERMITTIVITY
RELAXATION
SCANNING ELECTRON MICROSCOPY
SINTERING
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TITANATES
X-RAY DIFFRACTION