1 Cerâmica 2008 Vol: 54(332):. DOI: 10.1590/S0366-69132008000400009

Comportamento elétrico a alta temperatura de termistor cerâmico alfa-Fe2O3 com coeficiente de temperatura negativo

The electrical behavior of α-Fe2O3 dense ceramic, synthesized by Pechini method, was investigated by impedance spectroscopy in the frequency range from 5 Hz to 13 MHz. Electrical measurements were carried out from 298 K to 623 K in air. The evolution of the resistivity as a function of temperature shows a thermistor behavior with negative temperature coefficient. The grain conductivity as a function of temperature follows the Arrhenius law exhibiting an apparent activation energy for the electrical conduction process equal to 0.66 eV. The dielectric permittivity as a function of frequency and temperature shows a dispersion phenomenon at frequencies lower than 10 kHz, which increase with temperature increasing. The tangent loss tan δ shows a strong dispersion at low frequency and high temperature, around 573 K. A decrease of the loss magnitude occurs at frequencies > 104 Hz. A conduction mechanism of the hopping type is discussed.

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