抄録
Solid-state reaction between niobium (V) oxide and amorphous boron powders was carried out in a vacuum of 10−1 Pa at temperatures of 773K to 1773K for 1h. In the reaction at B/Nb2O5 molar ratios of 5.2 to 11.0 and 1773K, three kinds of niobium borides NbB, Nb3B4 and NbB2 were obtained. Single phases of NaB and NbB2 were obtained at the molar ratios of 5.7 and 8.2 to 10.6, respectively. However, when starting materials with the molar ratio of 7.0 were used, the Nb3B4 phase shows strongest relative X-ray intensities among NbB and NbB2 at 1773K. The lattice parameters of NbB and Nb3B4 are as follows: NbB (orthorhombic): a=0.3295 nm, b=0.8721 nm, c=0.3166 nm, Nb3B4 (orthorhombic): a=0.3302 nm, b=1.4076 nm, c=0.3142 nm. At the molar ratios of 8.2 to 10.6, lattice parameter of NbB2 (hexagonal) changed a=0.3111 nm∼0.3309 nm and c=0.3264 nm∼0.3308 nm.
