Combined computational and experimental investigation of the refractory properties of La_2Zr_2O_7

Abstract

We demonstrate how key material properties that provide guidance in the design of refractory materials can be accurately determined via ab initio thermodynamic calculations in conjunction with experimental techniques based on synchrotron X-ray diffraction and thermal analysis under laser-heated aerodynamic levitation. The properties considered include melting point, heat of fusion, heat capacity, thermal expansion coefficients, thermal stability and sublattice disordering, as illustrated in a motivating example of lanthanum zirconate (La_2Zr_2O_7). This work also sheds light on the unresolved controversy of possible phase transition before melting and identifies specific mechanisms responsible for the material's high melting point. This study benefits from the use of two very recent techniques: (i) a new small-cell coexistence method that enables the accurate and efficient determination of the melting points from ab initio calculations alone; (ii) the experimental determination of solid structure at high temperatures by high-temperature synchrotron X-ray diffraction of laser-heated aerodynamically levitated samples.

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