Order-disorder transition in Na0.25TiO2 bronze: Thermodynamic and crystallographic studies
Order-disorder transition in Na0.25TiO2 bronze: Thermodynamic and crystallographic studies
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Na0.25TiO2 青铜中的有序-无序转变：热力学和晶体学研究
DOI：
10.1016/0022-4596(88)90018-7
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发表时间：
1988
影响因子：
3.3
通讯作者：
M. Tournoux
中科院分区：
文献类型：
--
作者：
L. Brohan;R. Marchand;M. Tournoux
首次制备了一种化学计量的Wadsley青铜Na 0.25 tio2。二氧化钛骨架的钙钛矿样位置完全被钠离子占据。在室温下，空间群为P2 a或Pa，晶格参数为a= 12.177 (3) Å， b= 3.875× 4= 15.50 (2) Å， c= 6.480 (3) Å， β= 107.08(2)°。与著名的C2 m对称的Wadsley青铜相比，x射线和电子衍射图样在约b * 4处表现出额外的反射。在t3dc = 430 K时，出现了一个二阶跃迁。研究了η阶参数的平滑变化和异常比热。临界指数α⋍α′= 0.110±0.003和β= 0.324与重整化群法在d= 3和n= 1 （d=维数，n=阶参数分量数）下的计算结果吻合较好。
A stoichiometric Wadsley bronze Na 0.25 TiO 2 has been prepared for the first time. The perovskite-like sites of the TiO 2 framework are fully occupied by sodium ions. The space group, at room temperature, is P2 a or Pa and the lattice parameters are a= 12.177 (3) Å, b= 3.875× 4= 15.50 (2) Å, c= 6.480 (3) Å, β= 107.08 (2)°. As compared with those of the well-known Wadsley bronze of C2 m symmetry, X-ray and electron diffraction patterns exhibit extra reflections at about b∗ 4. At T 3D c= 430 K, a second-order transition appears. The smooth variation of the η-order parameter and the anomalous specific heat have been studied. The critical exponents α⋍ α′= 0.110±0.003 and β= 0.324 are in good agreement with those calculated from renormalization group method for d= 3 and n= 1 (d= dimensionality and n= number of order parameter components).