Problem of polymorphism and fusion of lanthanide trifluorides. II. Interaction of LnF/sub 3/ with MF/sub 2/ (M = Ca, Sr, Ba), change in structural type in the LnF/sub 3/ series, and thermal characteristics

Journal Article · Sun Feb 01 04:00:00 EST 1976 · J. Solid State Chem.; (United States)

DOI:https://doi.org/10.1016/0022-4596(76)90221-8· OSTI ID:7365447

Sobolev, B P ^[1]; Fedorov, P P; Seiranian, K B; Tkachenko, N L

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1. Inst. of Crystallography, Moscow

The results of a study on the interaction of LnF/sub 3/ with MF/sub 2/ (M = Ca, Sr, Ba) for 34 binary systems of the LnF/sub 3/--MF/sub 2/ type in the concentration range 60 to 100 mole percent LnF/sub 3/ are presented. It is shown that in this range the interaction of the components in the LnF/sub 3/--MF/sub 2/ systems is similar to that in the LnF/sub 3/--Ln/sub 2/O/sub 3/ systems. The problem of stabilizing different structural types of LnF/sub 3/ (tysonite and ..cap alpha..-YF/sub 3/) during the isomorphous substitution of Ln/sup 3 +/ by M/sup 2 +/ and 2F/sup -/ by O/sup 2 -/ with formation of solid--solid solutions Ln/sub 1-x/M/sub x/F/sub 3-x/ and LnF/sub 3-2x/O/sub x/, respectively, is discussed also. In congruent fusion of these phases, the coordinates of the maximum on the fusibility curve (according to composition) are regularly displaced to the side of pure LnF/sub 3/ with a decrease in the atomic number of the lanthanide. The vacancy-stabilized phases are typical examples of variable composition compounds (berthollides). On the basis of data on the interaction of components in the LnF/sub 3/--Ln/sub 2/O/sub 3/ and LnF/sub 3/--MF/sub 2/ systems, problems of polymorphism and changes of structural type in the LnF/sub 3/ series are discussed. Fusion and polymorphic transformation temperatures are given for LnF/sub 3/ with control of oxygen content in the specimens after thermal analysis.

• OSTI ID: 7365447
• Journal Information: J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 17:1-2; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
ANIONS
BINARY MIXTURES
CHARGED PARTICLES
CRYSTAL DEFECTS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIAGRAMS
DISPERSIONS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
IONS
MELTING POINTS
MIXTURES
PHASE DIAGRAMS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POINT DEFECTS
RARE EARTH COMPOUNDS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
VACANCIES