Structural, elastic, thermophysical and dielectric properties of zinc aluminate (ZnAl2O4)

Abstract

Dense zinc aluminate (gahnite) ceramics have been prepared at different sinter temperatures ranging from 1200 to 1600 °C from zinc aluminate powder prepared via the solid-state synthesis. A maximum achieved relative density of 93% was achieved. Several bulk properties like Young's modulus, heat capacity, thermal diffusivity and conductivity have been determined and estimations of the bulk properties at 100% density are made. Furthermore, in spinel-type materials like zinc aluminate the process of cation inversion occurs, which is in general not taken into account in computer simulations for the prediction of bulk properties. In order to determine whether the amount of cation inversion can be influenced by the preparation method resulting in different bulk properties, zinc aluminate powders were synthesised using solid-state synthesis, co-precipitation and a sol-gel method at different temperatures. The resulting powders were zinc deficient due to the volatile nature of zinc at the calcining temperatures. The cation inversion of these powders was investigated using solid-state MAS 27A1 NMR indicating that the cation inversion is very small for pure zinc aluminate irrespective of the preparation method.