Low-Temperature Structural Transitions in the Phonon-Glass Thermoelectric Material β-Zn₄Sb₃:  Ordering of Zn Interstitials and Defects

The low-temperature phase transitions of thermoelectric Zn 4 Sb 3 have been characterized using single-crystal X-ray diffraction, electrical resistance, and thermal conductivity measurements. Room-temperature stable, disordered β-Zn 4 Sb 3 undergoes a phase transition at 254 K to ordered α-Zn 4 Sb 3, which has an ideal composition Zn 13 Sb 10 . Below 235 K, a second low-temperature phase (α‘-Zn 4 Sb 3 ) can be detected. The sequence of phase transitions β−α−α‘ is reversible. The α−α‘ transformation originates from a slight Zn deficiency with respect to Zn 13 Sb 10 . The actual composition of Zn 4 Sb 3 is Zn 13 - δ Sb 10 .