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Abstract
Powder-absorption infrared (IR) spectra of perovskites CaFexTi1−x O3−x/2 (0≤x≤1) annealed at different temperatures were investigated at room temperature in the range 135–2000 cm−1. The spectra change as a function of composition, annealing temperature and structural state (order-disorder of oxygen vacancies). Autocorrelation analysis has been used to determine variations of average line widths of groups of peaks in the primary IR spectra. The band widths increase on increasing Fe content in the region of the structures with disordered oxygen vacancies and they decrease on going through the order-disorder boundary. High degrees of local structural heterogeneity are suggested by the effective line widths of the phases at intermediate compositions. The intensity of bands at ∼150 and ∼443 cm−1 decreases with increasing Fe content in the compositional range of the disordered structures. Finally, for every annealing temperature, the frequency of the band at ∼600cm−1 systematically shifts to higher values on increasing Fe content, these values decreasing again for the fully ordered structures.