Chemical processes involving volatile elements present an important problem in the synthesis of chemicals. This study proposes a theory-guided approach to the synthesis of solid solutions of Cu2ZnSn(SxSe1-x)(4) (CZTSSe), which contains two volatile elements (S and Se). We used thermodynamic modeling and phase diagram analysis to study the metastable sublimation and vaporization of all constituent elements and their important binary compounds in CZTSSe. Synthesis sequence was designed based on the calculated metastable sublimation and vaporization temperatures. An elemental solvo-thermal method without an autoclave was employed to synthesize single-phase CZTSSe with an average particle size of 500 nm and a band gap of 1.45 eV. The influence of synthesis parameters on the structural and physical properties of CZTSSe was also investigated. This study presents a facile and low-cost method for the synthesis of CZTSSe and, more importantly, outlines a number of general principles and conditions necessary for the synthesis of solid solutions involving volatile constituent elements. These findings contribute to both theoretical and experimental materials science. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.