TY - JOUR
T1 - Raman Spectroscopy and Microwave Properties of CaTiO3-Based Ceramics
AU - Zheng, H.
AU - Bagshaw, H.
AU - Csete de Györgyfalva, G. D.C.
AU - Reaney, I. M.
AU - Ubic, Rick
AU - Yarwood, J.
PY - 2003/9/1
Y1 - 2003/9/1
N2 - x CaTiO 3 –(1– x )Sr(Mg 1/3 Nb 2/3 )O 3 (CTSMN) and y CaTiO 3 –(1– y )NdAlO 3 (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 NdAlO 3 end member, which had the R ¯3 c space group, consistent with an a – a – a – tilt configuration. Sr(Mg 1/3 Nb 2/3 )O 3 (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.
AB - x CaTiO 3 –(1– x )Sr(Mg 1/3 Nb 2/3 )O 3 (CTSMN) and y CaTiO 3 –(1– y )NdAlO 3 (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 NdAlO 3 end member, which had the R ¯3 c space group, consistent with an a – a – a – tilt configuration. Sr(Mg 1/3 Nb 2/3 )O 3 (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.
UR - http://dx.doi.org/10.1063/1.1598271
UR - http://www.scopus.com/inward/record.url?scp=0141608049&partnerID=8YFLogxK
U2 - 10.1063/1.1598271
DO - 10.1063/1.1598271
M3 - Article
VL - 94
SP - 2948
EP - 2956
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 5
ER -