1307Sb2Te3 and Sb2Te2Se crystallize in the Bi2Se2S structure. The space group is R3m. The lattice constants for the hexagonal cell at 29°C are: a= 4.264_ 0.001 and c= 30.458 __ 0-007/~ for Sb2Te3, and a= 4.188 _+ 0.001 and c= 29.937 +_ 0.006 ~ for Sb2Te2Se. The fractional atom parameters were determined by a one-dimensional Fourier summation and by successive least-squares refinement of the 00l reflections, after intensity correction for Lorentz and polarization factors. The parameters for Sb2Te3 are: USb= -2-_0"3988, and ua'e1= ___0"7869; those for SbzTe2Se are" USb = +--0"3942 and U-re~=0"7854. The Te 2 or the Se respectively are in 0,0,0. The interatomic distances in Sb2Te3 are" Sb-Te1=2.979, Tel-Te 1= 3.736 and Sb-Te 2= 3.168 A. The corresponding distances for Sb2Te2Se are: Sb-Tel = 2-975, Tel-Tea= 3.753 and Sb-Se = 3-028 A. C lattice constant measurements on the Sb2Te3_ySey series show two regions with almost linear changes represented by the equations c = -0.529y + 30.465 for y_< 1 and c = -0.407y + 30.341 for 1 _

No abstract

No abstract

No abstract

Selected-area electron-diffraction patterns and x-ray diffraction powder patterns were taken of crushed single crystals of Pb