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Title: Acoustic phonon behavior of PbWO4 and BaWO4 probed by low temperature Brillouin spectroscopy
Authors: Kavitha, C.
Narayana, Chandrabhas
Ramachandran, B. E.
Garg, Nandini
Sharma, Surinder M.
Keywords: Condensed Matter Physics
Rare-earth tungstates
Crystal growth
Scheelite structure
Acoustic phonon
Gadolinium Molybdate
Calcium Tungstate
Issue Date: 2015
Publisher: Pergamon-Elsevier Science Ltd
Citation: Solid State Communications
Kavitha, C.; Narayana, C.; Ramachandran, B. E.; Garg, N.; Sharma, S. M., Acoustic phonon behavior of PbWO4 and BaWO4 probed by low temperature Brillouin spectroscopy. Solid State Communications 2015, 202, 78-84.
Abstract: Temperature dependent acoustic phonon behavior of PbWO4 and BaWO4 using Brillouin spectroscopy has been explained for the first time. Low temperature Brillouin studies on PbWO4 and BaWO4 have been carried out from 320-20 K. In PbWO4, we observe a change in acoustic phonon mode behavior around 180 K. But in the case of BaWO4, we have observed two types of change in acoustic phonon mode behavior at 240 K and 130 K. The change in Brillouin shift omega and the slope d omega/dT are the order parameter for all kinds of phase transitions. Since we do not see hysteresis on acoustic phonon mode behavior in the reverse temperature experiments, these second order phase transitions are no related to structural phase change and could be related to acoustic phonon coupled electronic transitions. In PbWO4 he temperature driven phase transition at 180 K could be due to changes in he environment around he lead vacancy (V-pb(2-)) changes the electronic states. In the case of BaWO4, the phase transition at 240 K shows he decrease in penetration depth of WO3 impurity. So it becomes more metallic. The transition at 130 K could be he same electronic transitions as that of PbWO4 as function of temperature. The sound velocity and elastic moduli of BaWO4 shows that it could be the prominent material for acousto-optic device applications. (C) 2014 Elsevier Ltd. All rights reserved.
Description: Restricted access
ISSN: 0038-1098
Appears in Collections:Research Articles (Chandrabhas N.)

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