Hydrothermal crystallization of a Ln2(OH)4SO4·nH2O layered compound for a wide range of Ln (Ln = La–Dy), thermolysis, and facile transformation into oxysulfate and oxysulfide phosphors (Hydrothermal crystallization of a Ln2(OH)4SO4∙nH2O layered compound for a wide range of Ln (Ln=La-Dy), thermolysis, and facile transformation into oxysulfate and oxysulfide phosphors)