Raman spectroscopy of B-site order–disorder in CaTiO3-based microwave ceramics

x CaTiO3–(1−x) Sr(Mg1/3Nb2/3)O3 (CTSMN) and y CaTiO3–(1−y) NdAlO3 (CTNA) were studied by Raman spectroscopy. A sharp Raman band at 825 cm−1 was observed in SrMg1/3Nb2/3O3, consistent with 1:2 long-range ordering of cations on the B-site. The intensity of this band decreased and its width increased with increasing x implying that the degree of order was reduced. A broad Raman band around 800 cm−1, absent in both pure CaTiO3 and NdAlO3, was found in CTNA solid solutions with the strongest intensity at x=0.5. The position and intensity of this band suggested that its origin was similar in nature to that observed in CTSMN. The occurrence of a band at ∼800 cm−1 in CTNA suggested a non-random distribution of Ti4+ and Al3+ on the B cation sites.