Synthesis and Structure Resolution of RbLaF₄

Abstract

The synthesis and structure resolution of RbLaF₄ are described. RbLaF₄ is synthesized by solid-state reaction between RbF and LaF₃ at 425 °C under a nonoxidizing atmosphere. Its crystal structure has been resolved by combining neutron and synchrotron powder diffraction data refinements (<i>Pnma,</i> <i>a</i> = 6.46281(2) Å, <i>b</i> = 3.86498(1) Å, <i>c</i> = 16.17629(4) Å, <i>Z</i> = 4). One-dimensional ⁸⁷Rb, ¹³⁹La, and ¹⁹F MAS NMR spectra have been recorded and are in agreement with the proposed structural model. Assignment of the ¹⁹F resonances is performed on the basis of both ¹⁹F–¹³⁹La <i>J</i>-coupling multiplet patterns observed in a heteronuclear DQ-filtered <i>J</i>-resolved spectrum and ¹⁹F–⁸⁷Rb HMQC MAS experiments. DFT calculations of both the ¹⁹F isotropic chemical shieldings and the ⁸⁷Rb, ¹³⁹La electric field gradient tensors using the GIPAW and PAW methods implemented in the CASTEP code are in good agreement with the experimental values and support the proposed structural model. Finally, the conductivity of RbLaF₄ and luminescence properties of Eu-doped LaRbF₄ are investigated