We report the temperature-and frequency-dependent dielectric spectrum of magnetite ceramic single phase samples at 77.4–300 K and 200 Hz–1 MHz.In temperature-dependent dc resistivity,the sharp transition expected in...We report the temperature-and frequency-dependent dielectric spectrum of magnetite ceramic single phase samples at 77.4–300 K and 200 Hz–1 MHz.In temperature-dependent dc resistivity,the sharp transition expected in single crystals is much suppressed.At higher temperatures,the grain boundaries contribute to the relaxation process.Below 120 K,the temperature-dependent dielectric constant reveals a weak broadened peak as cooling,from our analysis this behavior may be intrinsically correlated with the charge ordering of Fe^(3+) and Fe^(2+).Under a relatively low dc bias at 77.4 K,the polarization of the magnetite ceramic decreases,while under a much stronger electrical field,the dielectric spectrum in the lower frequency region is suppressed remarkably for the excitation of carriers bounded by grain boundaries.展开更多
基金Supported by the National Innovation Experiment Program for University Students,the National Natural Science Foundation of China under Grant No 10704054the Key Project of Natural Science Foundation of Tianjin(No 09JCZDJC18500).
文摘We report the temperature-and frequency-dependent dielectric spectrum of magnetite ceramic single phase samples at 77.4–300 K and 200 Hz–1 MHz.In temperature-dependent dc resistivity,the sharp transition expected in single crystals is much suppressed.At higher temperatures,the grain boundaries contribute to the relaxation process.Below 120 K,the temperature-dependent dielectric constant reveals a weak broadened peak as cooling,from our analysis this behavior may be intrinsically correlated with the charge ordering of Fe^(3+) and Fe^(2+).Under a relatively low dc bias at 77.4 K,the polarization of the magnetite ceramic decreases,while under a much stronger electrical field,the dielectric spectrum in the lower frequency region is suppressed remarkably for the excitation of carriers bounded by grain boundaries.
