Preparation of columbite MgNb2O6 and ZnNb2O6 ceramics by reaction-sintering

Columbite MgNb2O6 (MN) and ZnNb2O6 (ZN) ceramics produced by the reaction-sintering process were investigated. Secondary phases Mg0.652Nb0.598O2.25 and Mg0.66Nb11.33O29 were found in MgNb2O6 pellets. After 1250 °C sintering for 2 h, a density 4.85 g/cm3 (97.1% of the theoretical value) was obtained in MgNb2O6 pellets. In ZnNb2O6 pellets, no secondary phase formed. The maximum density 5.55 g/cm3 (98.7% of the theoretical value) occurs at 1200 and 1180 °C sintering for 2 and 4 h, respectively.