Tricritical point in ferroelastic ammonium titanyl fluoride: NMR study
- Institute of Chemistry, FEB RAS, Ave. Stoletiya, 159, 690022 Vladivostok (Russian Federation)
- Nikolaev Institute of Inorganic Chemistry, SB RAS, Ave. Lavrenteva, 3, 630090 Novosibirsk (Russian Federation)
Ionic mobility and phase transitions in ammonium titanyl pentafluoride (NH{sub 4}){sub 3}TiOF{sub 5} were studied using the {sup 19}F and {sup 1}H NMR data. The high-temperature phase (I) is characterized by spherically symmetric (isotropic) reorientation of [TiOF{sub 5}]{sup 3-} anions and by uniaxial reorientation of these anions in the ferroelastic phase II. A previously unknown second-order phase transition to the low-temperature modification (NH{sub 4}){sub 3}TiOF{sub 5}(III) was found at 205 K. The transition is accompanied by hindering of uniaxial rotations of [TiOF{sub 5}]{sup 3-} anions and by noticeable change of {sup 19}F magnetic shielding tensor associated with the influence of pseudo-Jahn-Teller effect. A pressure-induced tricritical point with coordinates p{sub TCR{approx}}2 kbar and T{sub TCR{approx}}170 K is estimated on the base of {sup 19}F NMR chemical shift data, and previously studied p-T diagram of (NH{sub 4}){sub 3}TiOF{sub 5}. - Graphical abstract: p-T phase diagram of (NH{sub 4}){sub 3}TiOF{sub 5}.
- OSTI ID:
- 21426621
- Journal Information:
- Journal of Solid State Chemistry, Vol. 183, Issue 9; Other Information: DOI: 10.1016/j.jssc.2010.07.027; PII: S0022-4596(10)00309-9; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMMONIUM COMPOUNDS
ANISOTROPY
CHEMICAL SHIFT
FLUORIDES
JAHN-TELLER EFFECT
MAGNETIC SHIELDING
NMR SPECTRA
PHASE DIAGRAMS
PHASE TRANSFORMATIONS
TEMPERATURE RANGE 0065-0273 K
TITANIUM COMPOUNDS
DIAGRAMS
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
INFORMATION
SHIELDING
SPECTRA
TEMPERATURE RANGE
TRANSITION ELEMENT COMPOUNDS