Hybrid Double Perovskite Containing Helium: [He2][CaZr]F6
Perovskites are of great technological and geological importance, in large part, due to their considerable compositional and structural flexibility. However, the formation of perovskites with neutral species on their A-sites is very unusual. The formation, phase transitions and properties of [He2][CaZr]F6, which is the first noble gas containing perovskite to be made, are reported. It is likely that a large family of related materials can also be prepared. On compression in neon, the negative thermal expansion (NTE) material CaZrF6 amorphizes at ~ 0. 5 GPa. However, on compression in helium at room temperature, gas is inserted into the structure to form a perovskite with helium on the A-site. This suppresses the amorphization until > 3 GPa. Volume versus pressure and Raman measurements suggest that filling of the A-site, to give [He2][CaZr]F6, is complete at > 1 GPa. The presence of helium on the A-site in this perovskite leads to a reduction in the magnitude of negative thermal expansion when compared to the parent phase CaZrF6, likely due to steric impediment of the transverse vibrational motion of fluoride. The helium also leads to considerable stiffening of the structure. At room temperature and ~2.5 GPa, the helium containing hybrid perovskite has a bulk modulus of ~ 47 GPa, whereas CaZrF6 has a bulk modulus of ~ 40 GPa at ambient. At 15 K, the cubic perovskite [He2][CaZr]F6 undergoes a structural phase transition, that likely involves a cooperative tilting of framework octahedra to give a lower-symmetry phase, which is tentatively assigned as tetragonal.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- AC02-06CH11357; FG02-94ER14466
- OSTI ID:
- 1813113
- Journal Information:
- Chemistry of Materials, Vol. 33, Issue 9; ISSN 0897-4756
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
Thermal Expansion and Response to Pressure of Double-ReO3 -Type Fluorides NaMVF6 (M = Nb, Ta)
Composition, response to pressure, and negative thermal expansion in MIIBIVF6 (M = Ca, Mg; B = Zr, Nb) [Composition, response to pressure, and negative thermal expansion in AIIBIVF6; A - Ca, Mg, B - Zr, Nb]