Phase Transition and Coefficients of Thermal Expansion in Al2−xInxW3O12 (0.2 ≤ x ≤ 1)

Materials

Michel B. Johnson¹  Mary Anne White¹  Victoria L. Blair²  Bojan A. Marinkovic³  Anja Dosen³  Andrés EstebanCerón Cortés³ 

[1] Clean Technologies Research Institute, Dalhousie University, Halifax, NS B3H 4R2, Canada;DEVCOM Army Research Laboratory, 6300 Rodman Rd. APG, Adelphi, MD 21005, USA;Department of Chemical and Materials Engineering, Pontifical Catholic University of Rio de Janeiro (PUC-Rio), Rio de Janeiro 22453-900, Brazil;

关键词: low thermal expansion;    AlInW₃O₁₂;    high-temperature XRPD;    dilatometry;    DSC;   

DOI  :  10.3390/ma14144021

来源: DOAJ

【 摘 要 】

Materials from theA₂M₃O₁₂ family are known for their extensive chemical versatility while preserving the polyhedral-corner-shared orthorhombic crystal system, as well as for their consequent unusual thermal expansion, varying from negative and near-zero to slightly positive. The rarest are near-zero thermal expansion materials, which are of paramount importance in thermal shock resistance applications. Ceramic materials with chemistry Al_2−xIn_xW₃O₁₂ (x = 0.2–1.0) were synthesized using a modified reverse-strike co-precipitation method and prepared into solid specimens using traditional ceramic sintering. The resulting materials were characterized by X-ray powder diffraction (ambient and in situ high temperatures), differential scanning calorimetry and dilatometry to delineate thermal expansion, phase transitions and crystal structures. It was found that the x = 0.2 composition had the lowest thermal expansion, 1.88 × 10⁻⁶ K⁻¹, which was still higher than the end member Al₂W₃O₁₂ for the chemical series. Furthermore, the AlInW₃O₁₂ was monoclinic phase at room temperature and transformed to the orthorhombic form at ca. 200 °C, in contrast with previous reports. Interestingly, the x = 0.2, x = 0.4 and x = 0.7 materials did not exhibit the expected orthorhombic-to-monoclinic phase transition as observed for the other compositions, and hence did not follow the expected Vegard-like relationship associated with the electronegativity rule. Overall, compositions within the Al_2−xIn_xW₃O₁₂ family should not be considered candidates for high thermal shock applications that would require near-zero thermal expansion properties.

【 授权许可】

Unknown