Solid structure of Li2BeF4 (FLiBe) from room temperature to melting studied by neutron and X‐ray diffraction

• 全文链接
• 请求原文

作   者：

D. Nathanael Gardner;  Haley Williams;  Sven C. Vogel;  Sean Fayfar;  Boris Khaykovich;  Shivani Srivastava;  Andrea Hwang;  Mark Asta;  David Sprouster;  Dan Olds;  Gregory Vershbow;  Jörg C. Neuefeind;  Raluca O. Scarlat; 

作者机构：

Stony Brook University;  University of Pennsylvania;  Massachusetts Institute of Technology;  University of California Berkeley;  Oak Ridge National Laboratory;  Brookhaven National Laboratory;  Los Alamos National Laboratory; 

关键词：

lattice parameters;  molten salt;  nuclear materials;  crystal structure;  neutron diffraction;  volume change upon melting;  FLiBe thermal expansion; 

期刊名称：

Journal of Applied Crystallography

i s s n：

0021-8898

年卷期：

2025 年 58 卷 2 期

页   码：

435-446

页   码：

摘   要：

Molten fluoride salts such as Li2BeF4 (FLiBe) are used in molten salt reactors, fluoride‐salt‐cooled high‐temperature reactors and fusion reactors as a fuel solvent, coolant and/or tritium breeding medium. In engineered systems that use molten salt, solid‐state material will be present during melting and freezing scenarios, and therefore the temperature‐dependent properties of the solid and solid/liquid phase transition merit investigation. To observe the behavior of the solid state of Li2BeF4 from room temperature to melting, this work used neutron and X‐ray diffraction to measure the changes in the lattice parameters and volume of the crystalline unit cell and compared the results with prior low‐temperature data for solid Li2BeF4. From neutron diffraction data it is also possible to identify anisotropy: centimetre‐scaled crystals align preferentially with the a axes parallel to the direction of freezing front propagation, and the c axes expand 54% more than the a axes. This work provides the lattice constants as a function of temperature, quantifies the thermal expansion, and determines the equation describing the change in density for solid Li2BeF4 from room temperature to 459°C to be ρsolid (kg m−3) = 2182 (3) − 0.115 (2) T (°C) and the volume expansion upon melting to be less than 5%. This density changes depending on molecular weight and enrichment.