NUCLEAR-MAGNETIC-RESONANCE OF BI-209 IN A BIVO4 SINGLE-CRYSTAL

Nuclear magnetic resonance spectra of Bi-209 (I = 9/2) in the ferroelastic BiVO4 single crystal has been investigated by employing a wide-line Varian spectrometer. Only three lines due to a large quadrupole interaction were measured at a fixed frequency of 6 MHz in the principal planes at room temperature. From the experimental data the quadrupole coupling constant e2qQ/h = 79.2 +/- 0.1 MHz and asymmetry parameter eta = 0.70 +/- 0.01 are determined; however, these values turn out to be quite different from the previous report obtained with a ceramic sample at liquid-nitrogen temperature. The principal axes of the electric field gradient tensor are determined for the first time, the x. y and z axes being the crystallographic c + 25-degrees, a + 25-degrees, and b axes. respectively. These directions are discussed in terms of the Bi-O bonds in the Bi-O polyhedra.