Thiophosphate phase diagrams developed in conjunction with the synthesis of the new compounds KLaP2S6, K2La(P2S6)(1/2)(PS4), K3La(PS4)(2), K4La0.67(PS4)(2), K9-xLa1+x/3(PS4)(4) (x = 0.5), K4Eu(PS4)(2), and KEuPS4

An alkali-metal sulfur reactive flux has been used to synthesize a series o f quaternary rare-earth metal compounds. These include KLaP2S6 (I), K2La(P2 S6)(1/2)(PS4) (II), K3La(PS4)(2) (III), K4La0.67(PS4)(2) (IV), K9-xLa1-x/3( PS4)(4) (x = 0.5) (V), K4Eu(PS4)(2) (VI), and KEuPS4 (VII). Compound I crys tallizes in the monoclinic space group P2(1)/c with the cell parameters a = 11.963(12) Angstrom, b = 7.525(10) Angstrom, c = 11.389(14) Angstrom, beta = 109.88(4)degrees and Z = 4. Compound II crystallizes in the monoclinic s pace group P2(1)/n with a = 9.066(6) Angstrom, b = 6.793(3) Angstrom c 20.1 12(7) Angstrom, P = 97.54(3)degrees, and Z = 4. Compound III crystallizes i n the monoclinic space group P2(1)/e with a = 9.141(2) Angstrom, b = 17.056 (4) Angstrom, c = 9.470(2) Angstrom, beta = 90.29(2)degrees, and Z = 4. Com pound IV crystallizes in the orthorhombic space group Ibam with a = 18.202( 2) Angstrom, b = 8.7596(7) Angstrom, c = 9.7699(8) Angstrom, and Z = 4. Com pound V crystallizes in the orthorhombic space group Ccca with a = 17.529(9 ) Angstrom, b = 36.43(3) Angstrom, c = 9.782(4) Angstrom, and Z = 8. Compou nd VI crystallizes in the orthorhombic space group Ibam with a 18.29(5) Ang strom, b = 8.81(2) Angstrom, c = 9.741(10) Angstrom, and Z = 4. Compound VI I crystallizes in the orthorhombic space group Pnma with a 16.782(2)Angstro m, b = 6.6141(6) Angstrom, c = 6.5142(6) Angstrom, and Z = 4. The sulfur co mpounds are in most cases isostructural to their selenium counterparts. By controlling experimental conditions, these structures can be placed in quas i-quaternary phase diagrams, which show the reaction conditions necessary t o obtain a particular thiophosphate anionic unit in the crystalline product . These structures have been characterized by Raman and IR spectroscopy and UV-vis diffuse reflectance optical band gap analysis.