Disappearance of ?AgI in (AgI)0.7?(NaPO3)0.3 composite at room temperature

We report crystalline phases in the melt-quenched (AgI)0.8–(NaPO3)0.2 and (AgI)0.7–(NaPO3)0.3 superionic composites at room temperature as studied by VEGA powder neutron diffraction of KEK. (AgI)0.8–(NaPO3)0.2 contains γAgI and βAgI with a 70:30 ratio, which is similar to that found in pure AgI. On the other hand, (AgI)0.7–(NaPO3)0.3 contains AgI and Ag5IP2O7 with a 53:47 ratio, without any indication of βAgI presence. Due to the overall broad line widths and the hexagonal-related orthorhombic unit cell of Ag5IP2O7, VEGA was indispensable to probe its existence in (AgI)0.7–(NaPO3)0.3 at room temperature. The disappearance of βAgI in (AgI)0.7–(NaPO3)0.3 in favour of Ag5IP2O7 containing more oxygens indicating that the phosphate chains have been oxidized to P2O7 pairs of phosphate tetrahedra.