Antiferrodistortive phase transition in EuTiO3

Antiferrodistortive phase transition in EuTiO3

Článek WoS

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 Pm3m to tetragonal I4/mcm due to antiphase tilting of oxygen octahedra along the c axis. 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 =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.

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 Pm3m to tetragonal I4/mcm due to antiphase tilting of oxygen octahedra along the c axis. 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 =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.

EuTiO3; phase transition; X-ray diffraction; infrared reflectivity

EuTiO3; phase transition; X-ray diffraction; infrared reflectivity

GOIAN, V.; KAMBA, S.; PACHEROVÁ, O.; DRAHOKOUPIL, J.; PALATINUS, L.; DUŠEK, M.; ROHLÍČEK, J.; SAVINOV, M.; LAUFEK, F.; SCHRANZ, W.; FUITH, A.; KACHLÍK, M.; MACA, K.; SHKABKO, A.; SAGARNA, L.; WEIDENKAFF, A.; BELIK, A.

2013

25.08.2012

AMER PHYSICAL SOC

ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844

1098-0121

PHYSICAL REVIEW B

86

054112

Spojené státy americké

054112-1

054112-9

9