Temperature-dependent Raman scattering study of the defect pyrochlores RbNbWO6 and CsTaWO6

被引:16
作者
Maczka, M. [1 ]
Knyazev, A. V. [2 ]
Majchrowski, A. [3 ]
Hanuza, J. [1 ]
Kojima, S. [4 ]
机构
[1] Polish Acad Sci, Inst Low Temp & Struct Res, PL-50950 Wroclaw 2, Poland
[2] Nizhnii Novgorod State Univ, Nizhnii Novgorod 603950, Russia
[3] Mil Univ Technol, Inst Appl Phys, PL-00908 Warsaw, Poland
[4] Univ Tsukuba, Inst Mat Sci, Tsukuba, Ibaraki 3058573, Japan
基金
日本学术振兴会;
关键词
CRYSTAL-STRUCTURE; TUNGSTEN BRONZES; PHASE-TRANSITION; RB; A(2)TI(2)O(7); SPECTRA; TA; LI; NA; NB;
D O I
10.1088/0953-8984/24/19/195902
中图分类号
O469 [凝聚态物理学];
学科分类号
070205 ;
摘要
Lattice dynamics calculations and temperature-dependent Raman scattering experiments were performed on RbNbWO6 and CsTaWO6 pyrochlore oxides. The observed bands were assigned to the respective motions of atoms in the unit cell. The spectra showed the presence of additional Raman bands not allowed for by the Fd (3) over barm cubic structure. We have shown that these bands appear due to both substitutional disorder in the 16c sites and displacive disorder of the A ions. Raman studies also revealed the presence of an additional 80 cm(-1) band at room temperature for RbNbWO6, not observed for CsTaWO6. The presence of this band has been attributed to off-center displacement of the Nb and W ions due to structural phase transition into a tetragonal ferroelectric phase. The temperature evolution of the 80 cm(-1) band intensity revealed that it disappeared at a much higher temperature (about 650 K) than the reported phase transition temperature (about 360 K). This behavior is reminiscent of chemically disordered perovskite ferroelectrics, including relaxor ferroelectrics, and was attributed to the presence of small polar regions with local tetragonal distortion embedded in the paraelectric matrix of the Fd (3) over barm structure.
引用
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页数:10
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共 56 条
[51]   Crystal growth, structure, and superconducting properties of the β-pyrochlore KOs2O6 [J].
Schuck, G ;
Kazakov, SM ;
Rogacki, K ;
Zhigadlo, ND ;
Karpinski, J .
PHYSICAL REVIEW B, 2006, 73 (14)
[52]   ACENTRICITY AND PHASE-TRANSITIONS FOR SOME AM2X6 COMPOUNDS [J].
SLEIGHT, AW ;
ZUMSTEG, FC ;
BARKLEY, JR ;
GULLEY, JE .
MATERIALS RESEARCH BULLETIN, 1978, 13 (11) :1247-1250
[53]   NH4CoAlF6: A pyrochlore-related phase existing in both ordered and disordered forms [J].
Subramanian, MA ;
Marshall, WJ ;
Harlow, RL .
MATERIALS RESEARCH BULLETIN, 1996, 31 (06) :585-591
[54]   Ferroelectric phase transition of Cd2Nb2O7 studied by Raman scattering [J].
Taniguchi, Hiroki ;
Shimizu, Takao ;
Kawaji, Hitoshi ;
Atake, Tooru ;
Itoh, Mitsuru ;
Tachibana, Makoto .
PHYSICAL REVIEW B, 2008, 77 (22)
[55]   Temperature evolution of the relaxor dynamics in Pb(Zn1/3Nb2/3)O3:: A critical Raman analysis -: art. no. 184106 [J].
Toulouse, J ;
Jiang, F ;
Svitelskiy, O ;
Chen, W ;
Ye, ZG .
PHYSICAL REVIEW B, 2005, 72 (18)
[56]   Low temperature symmetry of pyrochlore oxide Cd2Re2O7 [J].
Yamaura, J ;
Hiroi, Z .
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 2002, 71 (11) :2598-2600