The domain structure of the ferroelastic BiVO 4 single crystal has been investigated using the nuclear magnetic resonance (NMR) of 51 V and by the electron paramagnetic resonance (EPR) of the Mn 2+ ions contained in the crystal as an impurity. The 14 resonance lines of 51 V (I= 7 / 2 ) in a BiVO 4 crystal with the twin domain were measured in the crystallographic a-b (or c-b) and c-a (or a-c) planes with an FT NMR spectrometer. Two sets of Mn 2 + EPR signals were also obtained in the c-a plane. These two sets of NMR and EPR signals originate from the twin-domain structure. From these two sets of experimental data from 51 V NMR and Mn 2+ EPR, it is confirmed that the BiVO 4 single crystal has the prominent (W-plane) domain wall reported previously. The investigated domain structure is found to be stable with time in contrast with a previous report by Baran et al. The previous model of the twinning mechanism derived from NMR and X-ray diffraction data has been improved by employing the EPR results. The observed W plane of the domain wall in BiVO 4 can be explained by the ferroelastic species 4/mmm F 2/m instead of 4/m F 2/m.
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Yeom et al. (1994) studied this question.