X-ray diffraction on (AgI)0.7- (NaPO3)0.3 and (AgI)0.8- (NaPO3)0.2 composites

We have identified the crystallographic phases of the melt-quenched superionic composites (AgI)0.7- (NaPO3)0.3 and (AgI)0.8- (NaPO3)0.2 by X-ray diffraction. Measurements were made in a temperature range from 300 to 630 K. The materials have a glass phase and one or more crystalline phases. At 300 K and at 350 K, the crystalline phase contains a 30:70 mixture of \betaAgI and \gammaAgI. Above 350 K, the fraction of \betaAgI increases and at 403 K it is the dominant phase with a \beta- \gamma ratio of about 70:30 (slightly less in (AgI)0.8- (NaPO3)0.2). At 453, 523 and 623 K the crystalline material is mainly \alphaAgI. Crystalline 16-silver dodecaiodide diphosphate (Ag16I12P2O7) is also present between 373 and 523 K at a 5-10% level. It disappears at 623 K because the crystal melts.