Room-temperature vibrational properties of potassium gadolinium double tungstate under compression up to 32 GPa

KGd( WO4)(2) has been studied by high-pressure Raman spectroscopy at room temperature up to 32.2 GPa. Evidences of two pressure-driven phase transitions have been detected. The low-pressure monoclinic phase undergoes a phase transition at 7.2(+/- 0.9) GPa. The second transition is found at 14.2(+/- 1.6) GPa. Both transitions are reversible. No evidence of pressure-induced amorphization is found up to 32 GPa. The pressure dependence of the Raman active modes of the low-and high-pressure phases is reported. A Raman mode is detected to exhibit a weak softening in the low-pressure phase. Three Raman modes are also observed to have a similar behavior in the second high-pressure phase. The reported results are discussed comparing with the studies available in related tungstates. Emphasis is placed on the physical implications of the results. (C) 2015 Elsevier B.V. All rights reserved.