LAUSR

In the present work, a third form, the so-called HP-BiNbO4 synthesized at high pressure and high temperature is investigated with the in-situ angle-dispersive x-ray diffraction (ADXRD) measurements under high pressure. We explore the compression behavior and phase stability of HP-BiNbO4. The structure of HP-BiNbO4 is first determined. The x-ray diffraction data reveal that the structure HP-BiNbO4 is stable under pressures up to 24.1 GPa. The ADXRD data yield a bulk modulus K o = 185(7) GPa with a pressure derivative K o' = 2.9(0.8). Furthermore, the data are compared with those of other ABO4 compounds. The results show that the bulk modulus of HP-BiNbO4 (about 185 GPa) is slightly higher than that of tetragonal BiVO4 and significantly greater than those of the tungstates and molybdates.