High pressure phase transitions in scheelite structured fluoride: ErLiF{sub 4}

Journal Article · Tue Sep 15 04:00:00 EDT 2015 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2015.04.038· OSTI ID:22486761

Garg, Nandini; Mishra, A. K.; Poswal, H. K. ^[1]; Tyagi, A. K. ^[2]; Sharma, Surinder M ^[1]

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1. High Pressure and Synchrotron Radiation Physics Division, Mumbai (India)
2. Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

Our synchrotron based angle dispersive x-ray diffraction studies on scheelite structured ErLiF{sub 4} show that it undergoes two phase transitions, at ~11.5 and ~15.5 GPa to lower symmetry monoclinic phases, before becoming (irreversibly) amorphous at ~28 GPa. The first high pressure phase transformation to the fergusonite structure (space group I2/a) is found to be of thermodynamically second order. The second high pressure phase could be fitted to the P2/c space group, but detailed analysis rules out the wolframite structure (P2/c space group), common to many scheelite compounds under high pressures. We also suggest that despite the ionic character of the LiF{sub 4} tetrahedra, the compressibility of LnLiF{sub 4} (Ln=Eu–Lu) kind of scheelites is more affected by the LnF{sub 8} dodecahedra than the LiF{sub 4} tetrahedra. - Graphical abstract: Volume per formula unit of the scheelite and high pressure phases of ErLiF{sub 4} as a function of pressure. - Highlights: • ErLiF{sub 4} transforms to fergusonite and P2/c phase at high pressure. • Polyhedra of LnF{sub 8} affects compressibility of LnLiF{sub 4} (Ln=Eu–Lu) more than LiF{sub 4}. • Amorphization pressure varies inversely in LnLiF{sub 4} with ionic size of Ln cation. • In ErLiF{sub 4}a/c ratio reduces with pressure in contrast to reported increase in YLiF{sub 4}.

• OSTI ID: 22486761
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 229; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMORPHOUS STATE
COMPRESSIBILITY
ERBIUM COMPOUNDS
LITHIUM FLUORIDES
MONOCLINIC LATTICES
PHASE TRANSFORMATIONS
PRESSURE DEPENDENCE
WOLFRAMITE
X-RAY DIFFRACTION
YTTRIUM FLUORIDES