Synthese und Kristallstrukturen von α‐ und β‐Ba3(PS4)2 sowie von Ba3(PSe4)2

Synthesis and Crystal Structures of α‐, β‐Ba3(PS4)2 and Ba3(PSe4)2 Ba3(PS4)2 and Ba3(PSe4)2 were prepared by heating mixtures of the elements at 800 °C for 25 h. Both compounds were investigated by single crystal X‐ray methods. The thiophosphate is dimorphic and undergoes a displacive phase transition at about 75 °C. Both modifications crystallize in new structure types. In the room temperature phase (α‐Ba3(PS4)2: P21/a; a = 11.649(3), b = 6.610(1), c = 17.299(2) Å, β = 90.26(3)°; Z = 4) three crystallographically independent Ba atoms are surrounded by ten sulfur atoms forming distorted polyhedra. The arrangement of the PS4 tetrahedra, isolated from each other, is comparable with the formation of the SO42− ions of β‐K2SO4. In β‐Ba3(PS4)2 (C2/m; a = 11.597(2), b = 6.727(1), c = 8.704(2) Å; β = 90.00(3)°; Z = 2) the PS4 tetrahedra are no more tilted along [001], but oriented parallel to each other inducing less distorted tetrahedra and polyhedra around the Ba atoms, respectively. Ba3(PSe4)2 (P21/a; a = 12.282(2), b = 6.906(1), c = 18.061(4) Å; β = 90.23(3)°; Z = 4) is isotypic to α‐Ba3(PS4)2 and no phase transition could be detected up to about 550 °C.