Phase and morphology evolution of corundum-type Ni_4Nb_2O_9 powders synthesized by solid-state reaction

摘要

The solid-state mixed oxide method via a rapid vibro-milling technique is explored in the preparation of single-phase nickel diniobate (Ni_4Nb_2O_9) powders. The formation of the Ni_4Nb_2O_9 phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. It has been found that minor phases of unreacted NiO and Nb_2O_5 precursors and NiNb_2O_6 phase tend to form together with the Ni_4Nb_2O_9 phase, depending on calcination conditions. It is seen that optimization of calcination conditions can lead to a single-phase Ni_4Nb_2O_9 in an orthorhombic phase.