Dielectric anomaly of tungsten trioxide WO3 with giant dielectric constant

Temperature dependences of the dielectric constant and the dielectric dispersion of a WO, single crystal have been measured in the temperature range from -180 degrees C to 100 degrees C and at frequencies from 20 Hz to 1 MHz. A large dielectric anomaly has been observed at 16.2 degrees 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 Cr3+ 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(l) phase.