La2O2MQ2 phases: Stability and synthetic challenges

Oxychalcogenides containing transition metal or p block cations have potential for thermoelectric, photocatalytic and magnetic applications but the synthetic pathways to these quaternary phases are not fully understood. This presents a challenge to the design and preparation of new functional materials. Our combined experimental and computational study of La 2 O 2 MQ 2 ( M = +2 cation; Q = sulfide, selenide anion) systems explores the thermodynamic constraints on synthesis and highlights the subtle balance in stabilities of phases formed via competing reaction pathways. • Experimental and computational work to explore oxychalcogenide synthesis; • Successful synthesis requires a subtle balance of stabilities; • M2+ mobility may be a challenge for bulk synthesis by topochemical reaction.