CRYSTAL-STRUCTURE AND HYDROGEN OCCUPATION IN HXV2O5(X=0.0-3.9)

Changes in the crystal structure and the lattice constants of powdered crystalline V2O5 after absorption of hydrogen were measured, as a fun ction of the concentration, by X-ray diffractometry. The diffraction s pectra obtained showed that three kinds of phases, alpha (x < 0.4 in H xV2O5), beta (co-existing with either terminal phase in the range of 0 .4 less-than-or-equal-to x < 3.2) and gamma (3.2 less-than-or-equal-to x less-than-or-equal-to 3.9), appear up to x = 3.9, which was found t o be the upper limit of the absorption at 70-degrees-C under a hydroge n pressure of 5 M Pa. The crystal system of the three phases was deter mined to be orthorhombic, although the lattice constants differed. The diffraction lines were broadened, and the background of the X-ray spe ctra grew with hydrogenation, especially in the gamma-region, which in dicates the growth of the lattice distortion and a quasi-amorphous sta te. The occupation of hydrogen atoms in each phase is discussed on the basis of the experimental results.