Dielectric anomaly of tungsten trioxide WO3 with giant dielectric constant

Abstract

Temperature dependences of the dielectric constant and the dielectric dispersion of a WO₃ 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 10⁵. 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)