Citation: Mangstl, Martin; Wied, Jan Konrad; Weber, Johannes; Pritzel, Christian; Trettin, Reinhard; Schmedt auf der G\"unne, J\"orn (2019). Synthesis and characterization of methylammonium phosphates as crystalline approximants for anhydrous, low melting phosphate glasses. RSC Advances, 9, pp. 1822-1830.