Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9761659 | Solid State Ionics | 2005 | 9 Pages |
Abstract
This paper describes the preparation and phase relations between three stable polymorphs of Bi14WO24, which is the bismuth-rich neighboring phase of the high oxide-ion conductor, Bi7WO13.5. The low-temperature form crystallizes in the monoclinic system with the space group P21 or P21/m, Z = 12, a = 17.3796(4) Ã
, b = 17.3847(5) Ã
, c = 26.1636(9) Ã
, β = 90.279(2)°, and V = 7905.0(3) Ã
3. The intermediate form crystallizes in the orthorhombic system with the space group Pbnb, Z = 12, a = 26.132(1) Ã
, b = 17.4206(8) Ã
, c = 17.3201(8) Ã
, and VÂ =Â 7884.8(4) Ã
3. Both lattices shape a superstructure based on a δ-Bi2O3 related pseudo-fcc subcell through the transformation matrix (9/2, â 3/2, 0)/(1, 3, 0)/(0, 0, 3). A slight distortion of the orthorhombic cell generates the monoclinic cell. The high-temperature form is a good oxide-ion conductive fcc phase (a â 5.6 Ã
) isomorphous with δ-Bi2O3. On heating, the low-temperature form transforms to the intermediate form around 40 °C with a small transition enthalpy and a minute volume contraction; the intermediate form changes to the fcc form at 780 °C with a large transition enthalpy and a noticeable volume expansion. Both transitions are reversible. The 40 °C transition is displacive and the 780 °C transition reconstructive.
Keywords
Related Topics
Physical Sciences and Engineering
Chemistry
Electrochemistry
Authors
Akiteru Watanabe,