Ferroelectric yellow tungsten oxide is also called ferroelectric tungsten trioxide. It has been reported that tungsten trioxide has long been recognized as a ferroelectric material with a ferroelectric phase transition temperature of -40 °C. And ferroelectric behavior is an extremely important electrical property of tungsten trioxide materials.
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According to the experts, earlier inconclusive evidence for ferroelectricity in the structure of a low-temperature form of tungsten trioxide, ε-WO3, is confirmed. And ε-WO3 is the only form now shown to be acentric among at least six forms of WO3. The structure analysis of ε-WO3 was based primarily on Rietveld analysis of high-resolution neutron diffraction data obtained at 15 K. Higher resolution synchrotron X-ray diffraction data were used to confirm the space group. And it was found that this ε-form of WO3 is monoclinic. During the transformation from triclinic δ-WO3 to the monoclinic ε-WO3, no change in the octahedral tilt system occurs, but there are significant shifts in the W atom positions. These W atom shifts result in an enhancement of the long–short bond distance alternation in the [110] direction, which is related to changes in electrical and optical properties.
