title: High temperature and composition induced phase transitions in LiZnV₁-xAsxO₄ phenacites: Crystal structure and Raman spectroscopy studies.
abstract: In this work, using techniques of X-ray diffraction and Raman spectroscopy, we report the composition and high-temperature induced phase transition in the system LiZnV1-xAsxO4 (0⩽x⩽1). Both techniques showed that the increase of arsenic amount induced a structural transition from R-3 LiZnVO4 type to LiZnAsO4 type belonging to R3 space group, the transition occurring between x=0.7 and x=0.8. Furthermore, increasing temperature for the compositions (0.8⩽x⩽1) manifests a transition from the LiZnAsO4 structural type with R3 space group to the R-3 LiZnVO4 structural type. For this series, the transition from the space group R3 to the centro-symmetric space group R-3 shows considerable changes in the compositional and temperature dependencies of the bands: spectral positions of all the observed Raman bands exhibit shifts linearly proportional to the temperature increase, with points of shift-rate changes revealing a symmetry change. The Raman-spectra based temperature-composition phase diagram confirms the results obtained using the method of Rietveld refinements, thus showing the R-3 to R3 transition occurring between x=0.7 and 0.8.
authors.affiliation: Univ. Hassan 1er, Laboratoire des Sciences des Matériaux, des Milieux et de la modélisation (LS3M), 25000 Khouribga, Morocco. Electronic address: manounb@gmail.com.
authors.forename: B
authors.initials: B
authors.lastname: Manoun
authors.affiliation: Laboratoire de Physico-Chimie des Matériaux, Département de Chimie, FST Errachidia, Morocco.
authors.forename: M
authors.initials: M
authors.lastname: Azrour
authors.affiliation: Department of Earth Sciences, Uppsala University, SE-752 36 Uppsala, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Lazor
authors.affiliation: Laboratoire de Physico-Chimie des Matériaux, Département de Chimie, FST Errachidia, Morocco.
authors.forename: M
authors.initials: M
authors.lastname: Azdouz
authors.affiliation: Equipe Sciences de la matière condensée, Faculté des Sciences, Meknès, Morocco.
authors.forename: L
authors.initials: L
authors.lastname: Bih
authors.affiliation: Laboratory of Chemistry of Solid Materials, Department of Chemistry, Faculty of Sciences Ben M'Sik Casablanca, Morocco.
authors.forename: S
authors.initials: S
authors.lastname: Benmokhtar
authors.affiliation: Qatar Environment and Energy Research Institute, Qatar Foundation, P.O. Box 5825, Doha, Qatar.
authors.forename: R
authors.initials: R
authors.lastname: Essehli
authors.affiliation: Laboratoire de chimie de Solide Appliqué, Faculté des Sciences, Université Mohammed V, Rabat, Morocco.
authors.forename: L
authors.initials: L
authors.lastname: El Ammari
keywords: High temperature Raman spectroscopy; LiZnV(1−)(x)As(x)O(4); Phase transition; Phenacite structure; Rietveld refinements; X-ray diffraction