Berlin 2024 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 9: KFM Poster Session
KFM 9.20: Poster
Montag, 18. März 2024, 18:00–20:00, Poster E
Raman spectroscopy on KNbO3 single crystal: investigation of phase transitions, ferroelastic domains and dislocations — •Felix Drechsler1, Cameliu Himcinschi1, Oliver Preuß2, Xufei Fang2, and Jens Kortus1 — 1TU Bergakademie Freiberg, Institute of Theoretical Physics, D-09596 Freiberg, Germany — 2TU Darmstadt, Department of Materials and Earth Sciences, Division Nonmetallic-Inorganic Materials, D-64287 Darmstadt, Germany
We investigated a KNbO3 single crystal with Raman spectroscopy regarding phase transitions, ferroelastic domains and mechanically imprinted dislocations. In a temperature range between 150 K and 550 K the material passes two phase transitions from the rhombohedral crystal structure (C3v) at low temperatures to orthorhombic (C2v) at room temperature and to tetragonal (C4v) at high temperatures. A thermal hysteresis could be observed. Due to the changes in crystal structure, Raman spectroscopy is a suitable method to investigate phase transitions. With the help of 1D and 2D Raman mappings it was possible to determine the size of strip-like ferroelastic domains. We carried out extensive Raman investigations on mechanically imprinted dislocations in the ceramic KNbO3. There were clear differences in the Raman spectra between the dislocation areas and the pristine material. These were also observed in the temperature-dependent Raman measurements during the transition from rhombohedral to orthorhombic phase, which remained until the second phase transition. A correlation between dislocation density and peak position was also found.
Keywords: Ferroelectric Material; Dislocation; Ferroelastic Domain; Phase transition; Raman spectroscopy