Reactions of Lanthanides and Actinides in Molten Alkali Metal/Polychalcogenide Fluxes at Intermediate Temperatures (250-600 °C)

From the reaction of the elemental lanthanides and actinides in molten alkali metal/polychalcogenide salts, several new ternary compounds have been discovered. Specifically, these phases are K4USe8 (I) and ALnQ4 (II), where A = K, Ln = Ce or Tb, and Q = Se or A = Rb, Ln = Ce, Q = Te; and NaLnS3 (III), where Ln = La, Ce. The K4USe8 crystallizes in the orthorhombic space group Fdd2 (No. 43) with a = 17.331(4) A, b = 20.584(3) A, c = 8.811(3) A, Z = 8. The KCeSe4 crystallizes in the tetragonal space group P4/nbm (No. 125) with a = 6.376(2) A, c = 8.327(1) A, Z = 2. The KTbSe4 crystallizes in the tetragonal space group P4/nbm (No. 125) with a = 6.255(2) A, c = 8.227(1) A, Z = 2. The RbCeTe4 crystallizes in the tetragonal space group P4/nbm (No. 125) with a = 6.952(3) A, c = 9.084(4) A, Z = 2. The NaCeS3 crystallizes in the orthorhombic space group Pmmn (No. 59) with a = 5.683(1) A, b = 4.238(2) A, c = 9.802(2) A, Z = 2. The NaLaS3 crystallizes in the orthorhombic space group Pmmn (No. 59) with a = 5.752(4) A,...