Synthesis, crystal and electronic structure, and physical properties of the new lanthanum copper telluride La3Cu5Te7

The new lanthanum copper telluride La3Cu5−xTe7 has been obtained by annealing the elements at 1073 K. Single-crystal X-ray diffraction studies revealed that the title compound crystallizes in a new structure type, space group Pnma (no. 62) with lattice dimensions of a=8.2326(3) Å, b=25.9466(9) Å, c=7.3402(3) Å, V=1567.9(1) Å3, Z=4 for La3Cu4.86(4)Te7. The structure of La3Cu5−xTe7 is remarkably complex. The Cu and Te atoms build up a three-dimensional covalent network. The coordination polyhedra include trigonal LaTe6 prisms, capped trigonal LaTe7 prisms, CuTe4 tetrahedra, and CuTe3 pyramids. All Cu sites exhibit deficiencies of various extents. Electrical property measurements on a sintered pellet of La3Cu4.86Te7 indicate that it is a p-type semiconductor in accordance with the electronic structure calculations.