A Combined Theoretical and Experimental Raman Scattering Study of BaZrS3-BaHfS3 Solid Solutions.

Ba(Zr,Hf)S3 solid solutions are proposed for photovoltaic applications and a fast non-destructive measurement of the composition of these solutions and the identification of any possible secondary phases is a prerequisite for understanding their opto-electronic properties. Here we calculate the non-resonant one-phonon Raman spectra of pure BaHfS3 and BaZrS3, which show only subtle differences between them. To test this experimentally, a solution series of BaZr1-xHfxS3 (0≤x≤1) powders was synthesised and free of a secondary phase, HfS3 identified by 633 nm excitation Raman spectroscopy. The veracity of the synthesis method was confirmed by comparing X-ray diffractograms and optical absorption spectra of the BaZr0.5Hf0.5S3 solid solution to a 50:50 mixture of the pure ternary compounds. Experimental non-resonant Raman measurements on the solid solution powders confirm that only slight variations in the spectra are visible, making a solid solution composition determination difficult. However, exciting the solid solutions resonantly, leads to the appearance of new two-phonon modes in the Raman spectrum, which change significantly across the solid solution series. We consequently suggest that a rapid solid solution composition measurement can be made unambiguously by measuring the ratio of the intensities of the 825 cm-1 and 625 cm-1 Raman features.

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