On cooling (AgI)0.7(AgPO3)0.3 forms a glass which is a superionic conductor. We report neutron diffraction measurements that show the precipitate in the glass is crystalline β-AgI at room temperature. On heating, the precipitate shows a phase transformation to α-AgI at 435 K while pure AgI shows this transformation at 438 K. On cooling the reverse transformation takes place at 415 and 410 K, respectively.
