In Situ Diffraction from Levitated Solids Under Extreme Conditions-Structure and Thermal Expansion in the Eu2O3-ZrO2 System

• Published in: Journal of the American Ceramic Society Vol. 98; no. 4; pp. 1292 - 1299
• Main Authors: Maram, Pardha S., Ushakov, Sergey V., Weber, Richard J.K., Benmore, Chris J., Navrotsky, Alexandra
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01.04.2015
• Subjects: Anions; Cations; Cooling; Diffraction; Fluorite; Order-disorder transformations; Phase transformations; Solid solutions; Thermal expansion
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.13422

The accurate determination of structure and thermal expansion of refractory materials at temperatures above 1500°C is challenging. Here, for the first time, we demonstrate the ability to reliably refine the structure and thermal expansion coefficient of oxides at temperatures to 2200°C using in situ synchrotron diffraction coupled with aerodynamic levitation. Solid solutions in the Eu2O3–ZrO2 binary system were investigated, including the high‐temperature order–disorder transformation in Eu2Zr2O7. The disordered fluorite phase is found to be stable above 1900°C, and a reversible phase transition to the pyrochlore phase is noticed during cooling. Site occupancies in Eu2Zr2O7 show a gradual increase in disorder on both cation and anion sublattices with increasing temperature. The thermal expansion coefficients of all cubic solid solutions are relatively similar, falling in the range 8.6–12.0 × 10−6 C−1. These studies open new vistas for in situ exploration of complex structural changes in high‐temperature materials.