Investigation of factors affecting the stability of compounds formed by isovalent substitution in layered oxychalcogenides, leading to identification of Ba<sub>3</sub>Sc<sub>2</sub>O<sub>5</sub>Cu<sub>2</sub>Se<sub>2</sub>, Ba<sub>3</sub>Y<sub>2</sub>O<sub>5</sub>Cu<sub>2</sub>S<sub>2</sub>, Ba<sub>3</sub>Sc<sub>2</sub>O<sub>5</sub>Ag<sub>2</sub>Se<sub>2</sub> and Ba<sub>3</sub>In<sub>2</sub>O<sub>5</sub>Ag<sub>2</sub>Se<sub>2</sub>
Journal of materials chemistry. C