Structural investigation on a spinel-related Zn/Cr = 1 mixed-oxide system

Abstract

A Zn–Cr mixed oxide of 1/1 composition has been characterized by powder X-ray diffraction infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, differential thermal analysis–thermal gravimetry, surface-area determination and chemical analysis. The behaviour of the system has been studied over a large temperature range and under different activation atmospheres. In addition to the model involving a single non-stoichiometric spinel phase, already proposed in the literature, a model involving a shell rich in ZnCrO₄ and a core constituted by ZnCr₂O₄ and ZnO is discussed and shown to be consistent with the experimental evidence.