Preparation of NiNb₂O₆ Columbite Ceramics by a Reaction-Sintering Process

Abstract

Preparation of NiNb 2 O 6 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 NiNb 2 O 6 ceramics were obtained after being sintered at 1250-1450 o C for 2 h and 4 h from mixture of Nb 2 O 5 and 50%Ni(NO 3 ) 2 -50%NiO (NN1). In pellets from mixture of Nb 2 O 5 and NiO (NN2), columbite NiNb 2 O 6 ceramics were obtained after being sintered at 1150-1350 o C for 2 h and 4 h. A density of 4.47 g/cm 3 was obtained in NN1 for 2 h sintering at 1400 o C. For NN2, a higher density 5.62 g/cm 3 (99.8% of the theoretical value) was obtained for 2 h sintering at 1300 o C. The reaction-sintering process has proven to be a simple and effective method in preparing columbite NiNb 2 O 6 ceramics. A higher density could be obtained at lower sintering temperature by using NiO instead of 50%Ni(NO 3 ) 2 -50%NiO in the reaction with Nb 2 O 5 .

Synthesis of temperature-stable microwave dielectric ceramics NiNb2O6 with TiO2 addition

“…Grains with a size of 1 m at 1200 • C and those with a size of 3.4 m at 1270 • C could be found in the NNT8 ceramics. In our study of the NiNb 2 O 6 ceramics prepared via the reaction-sintering process, grains with a size of 1-3.2 m at 1200-1300 • C could be found [16]. The addition of 8 mol% TiO 2 facilitated the grain growth process.…”

Effect of CuO on CaTiO3 perovskite ceramics prepared using a direct sintering process

“…Raw materials PbO and Nb 2 O 5 were mixed with Mg(NO 3 ) 2 or Fe(NO 3 ) 3 then pressed and sintered directly into PMN and PFN ceramics. These are the first successful synthesis of perovskite relaxor ferroelectric ceramics without having to go through the calcination step in the conventional solid-state route or in the columbite/wolframite route (two calcination steps were 6 were also prepared successfully via this reaction-sintering process [33][34][35][36][37]. In the present study, synthesis of CaTiO 3 ceramics by a reaction-sintering process and the effect of CuO addition were investigated.…”

Non-calcining process for CuAlO2 and CuAl0.9Ca0.1O2 ceramics

“…Other Pb-based complex perovskite ceramics were also produced by this reaction-sintering process successfully. In recent studies, some microwave dielectric ceramics such as BaTi 4 and NiNb 2 O 6 were also prepared successfully via this reactionsintering process [20][21][22][23][24]. In this study, synthesis of CuAlO 2 and CuAl 0.9 Ca 0.1 O 2 ceramics using a reaction-sintering process were investigated.…”