When human tooth enamel is heated either invacuum or air it presents drastic changes in electricalsusceptibility, conductivity and structural properties. In thispaper we report an insulator-conductive transition which isobserved in air around 350℃ where enamel conductivitychanges drastically and its electrical resistance decreasesfrom 1015 to 105 Ω;that is, it goes from an insulator to asuper-ionic ceramic behavior. This transition, first evidencedin vacuum by electron microscopy observations, is nowcompletely determined by a.c. impedance spectroscopytechnique and its characterizations, was carried out as afunction of the frequency and temperature. X-ray in situheating diffraction experiments show that there is nostructural phase transition during a wide range of temperatureincluding the one where the conductivity transition occurs.
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