Synchrotron-radiation X-ray powder diffraction study of /spl alpha/- and /spl beta/-Zn/sub 4/Sb/sub 3/ compounds

The crystal structures of the /spl alpha/- and /spl beta/-Zn/sub 4/Sb/sub 3/ have been investigated by the synchrotron-radiation X-ray powder diffraction at temperatures of 180 to 295 K. The Rietveld analysis indicates that the /spl alpha/-Zn/sub 4/Sb/sub 3/ possesses a rhombohedral structure with R-3c as the /spl beta/-Zn/sub 4/Sb/sub 3/ does. The /spl beta/- to /spl alpha/-phase structural transition is of 2nd order and accompanies the reduction in the c/a and increase in volume (/spl Delta/a/a>0 and /spl Delta/c/c<0). The atomic displacement parameters and bond distance are calculated.