Nuclear Magnetic Resonance of ⁵¹V in BiVO₄ Single Crystals

Abstract

Nuclear magnetic resonance spectra of 51V (I=7/2) in ferroelastic BiVO4 single crystals grown by the Czochralski method have been investigated by employing a wide-line Varian spectrometer. The seven line structure due to the quadrupole interaction was measured at a fixed frequency of 15 MHz in three mutually perpendicular crystal planes at room temperature and 77 K, well below its ferroelastic Curie temperature of 523 K. From the experimental data the quadrupole coupling constant, e 2 q Q/h, and asymmetry parameter, η, are determined: e 2 q Q/h=4.856 MHz and η=0.380 at room temperature, and 5.062 MHz and 0.459, respectively, at 77 K. The principal axes of the electric field gradient tensor are X=c, Y=a, and Z=b, where a,b, and c are crystal axes with β=90.38°. The twin structure of some of the crystals is also observed.

Orientation of electric field gradient and chemical shift tensors in BiVO4 at room temperature by51V NMR

“…3 Euler angles between principal axis systems of the two interactions (0^16¡, 66^9¡, 169^14¡) were determined and satisfy the crystallographic symmetries. However, this orientation is only consistent with the results of Choh et al 4 if the b angle is regarded as 90¡.…”

“…The lineshape is mainly governed by the CSA, whose parameters can thus be extracted with good reliability. The measured span of the CSA is slightly greater than the result reported by Lapina et al 3 The reÐnement exe- (6,8,4) cuted with the previously reported quadrupolar parameters (s \ 4.8 MHz and gives the same result g Q \ 0.38) for the CSA parameters. Even when the quadrupolar interaction is set to zero, the CSA parameters remain unchanged.…”

Low-Symmetry Aspects in EPR Spectra of Mn2+at Bi3+Sites in BiVO4Single Crystal

“…Recently, a number of experiments, e.g. X-ray and neutron diffraction [5], Raman scattering [6][7][8], NMR [9][10][11][12], and EPR [13][14][15][16] have been carried out to investigate structural changes, phase transitions, and optical properties of BiVO4. EPR is a powerful technique in studies of local site symmetry around paramagnetic impurities in crystals.…”