Synthesis of Defect Perovskites (He2–x⟂x)(CaZr)F6 by Inserting Helium into the Negative Thermal Expansion Material CaZrF6
- Georgia Inst. of Technology, Atlanta, GA (United States)
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Defect perovskites (He2–x⟂x)(CaZr)F6 can be prepared by inserting helium into CaZrF6 at high pressure. They can be recovered to ambient pressure at low temperature. There are no prior examples of perovskites with noble gases on the A-sites. The insertion of helium gas into CaZrF6 both elastically stiffens the material and reduces the magnitude of its negative thermal expansion. It also suppresses the onset of structural disorder, which is seen on compression in other media. Measurements of the gas released on warming to room temperature and Rietveld analyses of neutron diffraction data at low temperature indicate that exposure to helium gas at 500 MPa leads to a stoichiometry close to (He1⟂1)(CaZr)F6. Helium has a much higher solubility in CaZrF6 than silica glass or crystobalite. An analogue with composition (H2)2(CaZr)F6 would have a volumetric hydrogen storage capacity greater than current US DOE targets. We anticipate that other hybrid perovskites with small neutral molecules on the A-site can also be prepared and that they will display a rich structural chemistry.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1399917
- Journal Information:
- Journal of the American Chemical Society, Vol. 139, Issue 38; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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