Preparation of NiNb₂O₆ Columbite Ceramics by a Reaction-Sintering Process

Abstract

Preparation of NiNb₂O₆ columbite ceramics by a reaction-sintering process has been investigated. The mixture of raw materials was pressed and sintered into ceramics without any calcination stage involved. Columbite NiNb₂O₆ ceramics were obtained after being sintered at 1250–1450°C for 2 h and 4 h from mixture of Nb₂O₅ and 50%Ni(NO₃)₂-50%NiO (NN1). In pellets from mixture of Nb₂O₅ and NiO (NN2), columbite NiNb₂O₆ ceramics were obtained after being sintered at 1150–1350°C for 2 h and 4 h. A density of 4.47 g/cm³ was obtained in NN1 for 2 h sintering at 1400°C. For NN2, a higher density 5.62 g/cm³ (99.8% of the theoretical value) was obtained for 2 h sintering at 1300°C. The reaction-sintering process has proven to be a simple and effective method in preparing columbite NiNb₂O₆ ceramics. A higher density could be obtained at lower sintering temperature by using NiO instead of 50%Ni(NO₃)₂-50%NiO in the reaction with Nb₂O₅.