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 Zn4Sb3 have been characterized using single-crystal X-ray diffraction, electrical resistance, and thermal conductivity measurements. Room-temperature stable, disordered beta-Zn4Sb3 undergoes a phase transition at 254 K to ordered alpha-Zn4Sb3, which has an ideal composition Zn13Sb10. Below 235 K, a second low-temperature phase (alpha'-Zn4Sb3) can be detected. The sequence of phase transitions beta-alpha-alpha' is reversible. The alpha-alpha' transformation originates from a slight Zn deficiency with respect to Zn13Sb10. The actual composition of Zn4Sb3 is Zn13-delta Sb10.