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Phase transition in single crystal Cs2Nb4O11.
Jianjun Liu1, E P Kharitonova, Chun-Gang Duan
1Department of Physics, University of Nebraska, Omaha, Nebraska 68182-0266, USA. jliu@unlserve.unl.edu
The Journal of Chemical Physics
|April 26, 2005
Summary
A structural phase transition in cesium niobate (Cs2Nb4O11) was identified at 165°C, evidenced by anomalies in capacitance and Raman spectra, indicating a shift from Pnn2 to Imm2 symmetry.
Area of Science:
- Solid-state chemistry
- Materials science
- Crystallography
Background:
- Cesium niobate (Cs2Nb4O11) is a material with potential applications, but its phase transitions are not fully understood.
- Understanding structural dynamics is crucial for predicting and controlling material properties.
Purpose of the Study:
- To investigate the temperature-dependent phase transition in single crystal Cs2Nb4O11.
- To elucidate the structural changes associated with observed anomalies in physical properties.
Main Methods:
- Temperature-dependent complex capacitance and impedance measurements.
- Polarized Raman spectroscopy across a range of temperatures.
- Pseudosymmetry search of structure space group for crystallographic analysis.
Main Results:
- A sharp lambda-shaped peak in complex capacitance observed at 165°C.
- Drastic changes in polarized Raman spectra correlated with the capacitance anomaly.
- Structural transition identified from orthorhombic Pnn2 to orthorhombic Imm2 at 165°C.
- Assignment of high-wavenumber Raman bands to internal vibrations of NbO6 octahedra and NbO4 tetrahedra.
Conclusions:
- The study confirms a structural phase transition in Cs2Nb4O11 at 165°C.
- The transition involves a change in crystal symmetry from Pnn2 to Imm2.
- Raman spectroscopy provides insights into the vibrational modes of the niobate polyhedra during the transition.