Raman studies of some alkali metal–lanthanide double tungstates at high pressures
✍ Scribed by A. Jayaraman; S. K. Sharma; S. Y. Wang
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 312 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0377-0486
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✦ Synopsis
Pressure-induced phase transitions in Ðve alkali metal-lanthanide double tungstates, were investi-ALn(WO 4 ) 2 , gated using high-pressure Raman spectroscopy in the range 0-35 GPa. A phase transition in the scheelite-type double tungstates and to a distorted monoclinic type occurs near 10 NaSm(WO
) 2 GPa. In the pseudo-scheelite-type a similar pressure-induced transition occurs. The behavior is com-KLa(WO 4 ) 2 pared with the scheelite-type and it is proposed that the local compressibility di †erence at the cationic sites SrWO 4 drives the transition in the Na and K double tungstates. The results suggest that the scheelite-type lattice becomes unstable near 10 GPa. In which has the structure (wolframite-like), a sluggish LiY(WO
) 2 -type phase transition to a di †erent monoclinic lattice occurs, which upon release of pressure reverts to the wolframitetype structure. A brief account of the crystal chemistry of the alkali metal-lanthanide double tungstates from the extensive Russian literature is presented to obtain an insight into the pressure-induced phase transitions in them.