A-B INVERSION IN QUARTZ FROM LOW FREQUENCY ELECTRICAL IMPEDANCE SPECTROSCOPY

The a-b phase transformation in quartz has been studied in the pressure range from 0.5 to 2.5 GPa by the use of the low frequency electrical impedance spectroscopy. The electrical conductivity data obtained at low frequencies exhibit a different slope on an Arrhenius plot ln(sLFD*T) vs. 1/T above and below Tc, where T is the absolute and Tc is the inversion temperature. The point where the slope changes, coincide with the Tc, i.e. the temperature point of a-b inversion in quartz. The obtained inversion temperature Tc from this method compares well with the previous measurements of Tc using DTA and laser interferometry. The low frequency dispersion data in insulating materials with the ionic conductivity due to impurities may be a useful method for characterization of structural displacive phase transitions in quartz-like structures. 40 refs.