A simple synthetic approach to BaZrS3, BaHfS3, and their solid solutions

A simple synthetic approach to BaZrS3, BaHfS3, and their solid solutions is presented and discussed here. The synthesis is performed under relatively mild conditions (T = 500°C) and is complete in a few hours. The reactants are powdered BaS, Me (Me: Zr, Hf) and S in a ratio 1:1:3, mixed and sealed under vacuum in borosilicate glass ampoules. No purification is usually required, and the yield is quantitative. The low synthesis temperature allows for the use of borosilicate glass as container material instead of silica glass, thus lowering the costs and simplifying the sealing of the reaction vessel; furthermore, the use of expensive ZrS2 and HfS2 is avoided. The same procedure was successfully used for the synthesis of solid solutions BaHf1-xZrxS3 that were always obtained as crystalline single-phase materials. The solid solutions display optical and structural properties that vary in a linear fashion with the composition and are intermediate between those of BaZrS3 and BaHfS3. The possibility of varying the band gap of the material between 1.78 (BaZrS3) and 2.11 eV (BaHfS3) in a continuous way by simply adjusting the Hf/Zr ratio is very intriguing for potential applications in multi-junction and in-door photovoltaic applications and light emitting devices.