ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Components interaction in the systems (LiF–CaF₂)_eut–nLnF₃ (Ln = Nd, Sm, Gd)

Oksana Matselko, Zuzana Netriová, Jarmila Mlynáriková, Blanka Kubíková, Jaroslav Rusnák, and Miroslav Boča

Institute of Inorganic Chemistry, Slovak Academy of Sciences, Bratislava, Slovakia

E-mail: oksana.matselko@savba.sk

Received: 3 July 2025  Accepted: 25 November 2025

Abstract:

Spontaneously cooled samples of the systems (LiF–CaF₂)_eut–nLnF₃ (Ln = Nd, Sm, Gd; n = 0.01–0.4 for Nd and Sm, and 0.01–0.3 for Gd) have been reexamined using X-ray powder diffraction to clarify the composition of previously unidentified phases. For these systems, apart from the crystallisation of LiF, NdF₃ (Ln = Nd; n > 0.01), Ca_ySm_1−yF_3−y (Ln = Sm; n > 0.01), or LiGdF₄ (Ln = Gd; n ≥ 0.03), the formation of cubic phases Ca_1−xLn_xF_2+x (x ≈ 0.2–0.35 for Nd, 0.16–0.39 for Sm, and 0.17–0.32 for Gd) with a fluorite-related structure is observed. Initial compositions of these cubic phases were calculated based on the determined cell parameters and refined using the CeH₃ crystal structure model. Phases Ca_1−xLn_xF_2+x (fluorite-related structure) and Ca_ySm_1−yF_3−y (tysonite-type structure) are forming due to the isomorphous heterovalent substitution and known to be characterised by numerous defects in their crystal structures. Assuming that the formation of nonstoichiometric phases Ca_1−xLn_xF_2+x and Ca_ySm_1−yF_3−y leads to enhanced conductivity, ac conductivity measurements were performed at room temperature for (LiF–CaF₂)_eut–nLnF₃ samples (n = 0.15, 0.3) in the frequency range of 1 kHz–1 MHz to evaluate their presence and effect.

Graphical abstract

Keywords: Ac conductivity; Crystal structure; Fluorite-type; Rare earth fluoride; Spontaneously cooled molten system; X-ray powder diffraction

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04556-w

Chemical Papers 80 (5) 4671–4684 (2026)