Thermal induced structural properties of silver(I) sulphate (Ag sub(2)SO sub(4))

The crystal structures of silver(I) sulphate, Ag sub(2)SO sub(4), have been investigated as a function of temperature. A main feature is the phase transition from the low-temperature ordered phase, F ddd, to the high-temperature disordered phase, [Formulaomitted]. In particular, the high-temperature structure is solved from single crystal synchrotron X-ray measurements. In this phase the title compound undergoes a colossal (anisotropic) thermal expansion of [Formulaomitted]. This is presumably owing to a high anisotropic vibration state of one of the two crystallographically independent Ag-atoms. Simultaneously occurring high ionic conductivity may be associated with silver ions moving along the [Formulaomitted]-axis using a "paddle-wheel" assisted percolative mechanism. Onset of metallic silver in the single crystals is documented, seemingly dependent on thermal pre-history, mosaic structure and chemical synthesis. Possible mechanisms explaining this effect, comprising disproportionation or photo-decomposition, are suggested. Silver (I) sulphate, Ag sub(2)SO sub(4), is a common chemical compound used in many contexts. Surprisingly, its high temperature structure and the corresponding properties have not been elucidated until now. By use of synchrotron radiation diffraction techniques, the (disordered) structure is here reported and an anisotropic colossal thermal expansion effect is documented. The spatial arrangements of the silver-atoms explain this behavior, and also the known high thermal conductivity.