期刊
PHYSICAL REVIEW B
卷 86, 期 5, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.86.054112
关键词
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资金
- Czech Science Foundation [P204/12/1163]
- MSMT [MP0904, LD12026, LD11035]
- Project Praemium Academiae of ASCR
- Austrian Science Found (FWF) [P23982-N20]
- Austrian Science Fund (FWF) [P23982] Funding Source: Austrian Science Fund (FWF)
- Austrian Science Fund (FWF) [P 23982] Funding Source: researchfish
X-ray diffraction, dynamical mechanical analysis, and infrared reflectivity studies revealed an antiferrodistortive phase transition in EuTiO3 ceramics. Near 300 K, the perovskite structure changes from cubic Pm (3) over barm to tetragonal I4/mcm due to antiphase tilting of oxygen octahedra along the c axis (a(0)a(0)c(-) in Glazer notation). The phase transition is analogous to SrTiO3. However, some ceramics as well as single crystals of EuTiO3 show different infrared reflectivity spectra bringing evidence of a different crystal structure. In such samples, electron diffraction revealed an incommensurate tetragonal structure with modulation wave vector q similar or equal to 0.38 a*. Extra phonons in samples with modulated structure are activated in the IR spectra due to folding of the Brillouin zone. We propose that defects such as Eu3+ and oxygen vacancies strongly influence the temperature of the phase transition to antiferrodistortive phase as well as the tendency to incommensurate modulation in EuTiO3.
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