X-ray diffraction on ${(\text{AgI})}_{0.7}$– ${({\text{NaPO}}_3)}_{0.3}$ and ${(\text{AgI})}_{0.8}$– ${({\text{NaPO}}_3)}_{0.2}$ composites

Abstract

We have identified the crystallographic phases of the melt-quenched superionic composites ${(\text{AgI})}_{0.7}$– ${({\text{NaPO}}_3)}_{0.3}$ and ${(\text{AgI})}_{0.8}$– ${({\text{NaPO}}_3)}_{0.2}$ 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 $\text{beta}$AgI and $\text{gamma}$AgI. Above 350 K, the fraction of $\text{beta}$AgI increases and at 403 K it is the dominant phase with a $\text{beta}$– $\text{gamma}$ ratio of about 70:30 (slightly less in ${(\text{AgI})}_{0.8}$– ${({\text{NaPO}}_3)}_{0.2}$). At 453, 523 and 623 K the crystalline material is mainly $\text{alpha}$AgI. Crystalline 16-silver dodecaiodide diphosphate (${\text{Ag}}_{16}{\text{I}}_{12}{\text{P}}_2{\text{O}}_7$) is also present between 373 and 523 K at a 5–10% level. It disappears at 623 K because the crystal melts.