Dielectric anomaly of tungsten trioxide WO₃ with giant dielectric constant

Abstract

Abstract Temperature dependences of the dielectric constant and the dielectric dispersion of a WO 3 single crystal have been measured in the temperature range from –180 °C to 100 °C and at frequencies from 20 Hz to 1 MHz. A large dielectric anomaly has been observed at 16.2 °C on heating, and the peak value of the dielectric constant is as large as about 10 5 . The anomaly has large thermal hysteresis, long relaxation time and large dielectric dispersion. A transition from ferrielectric state to ferroelectric state induced by an electric field has been observed by D – E hysteresis measurement below room temperature. In the triclinic phase, the coexistence of the monoclinic(II) and the monoclinic(I) phases was observed by EPR (ESR) measurements of doped Cr +3 ions. These results suggest that a frustration of the antiferroelectric and ferroelectric states exists at the dielectric anomaly temperature. The dielectric anomaly can be interpreted as a result of the phase transition between the triclinic phase with micro ferroelectric regions and the antiferroelectric monoclinic(I) phase. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)