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Raman Spectroscopy and Microwave Properties of CaTiO3-Based Ceramics
Journal of Applied Physics (2003)
  • H. Zheng
  • H. Bagshaw
  • G. D.C. Csete de Györgyfalva
  • I. M. Reaney
  • Rick Ubic, Boise State University
  • J. Yarwood, Sheffield Hallam University

xCaTiO3–(1–x)Sr(Mg1/3Nb2/3)O3 (CTSMN) and yCaTiO3–(1–y)NdAlO3 (CTNA) microwave ceramics have been studied by x-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. TEM and XRD revealed that all compositions underwent octahedral tilt transitions on cooling, generally resulting in an a–a–c+ tilt system. The exception was the NdAlO3 end member, which had the R¯3c space group, consistent with an a–a–a– tilt configuration. Sr(Mg1/3Nb2/3)O3 (SMN), (x = 0) also exhibited +/–1/3{hkl} reflections in x-ray and electron diffraction patterns associated with 1:2 long-range ordering of the B-site cations. For x≥ 0.2, no 1:2 ordered reflections were observed. The long-range B-site ordering in SMN gave rise to sharp Raman bands at 391 and 825 cm–1. The 391 cm–1 band disappeared for x≥ 0.2 and the width of the 825 cm–1 band became broader as x increased. It was concluded that for samples with x≥ 0.2, only short-range ordering remained which decreased in correlation length as x increased. In CTNA solid solutions, a broad Raman band occurred at ~800 cm–1 (absent for y = 0 and 1 and strongest for y = 0.5). The position of this band suggested that its origin was similar in nature to the ~825 cm–1 band observed in CTSMN and therefore related to local short-range cation ordering. A relation between the presence of strong local order and poor Q in zero-temperature coefficient of the resonant frequency CTSMN (x ≈ 0.2) is postulated.

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Citation Information
H. Zheng, H. Bagshaw, G. D.C. Csete de Györgyfalva, I. M. Reaney, et al.. "Raman Spectroscopy and Microwave Properties of CaTiO3-Based Ceramics" Journal of Applied Physics Vol. 94 Iss. 5 (2003)
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