We present the structural, electronic, vibrational, and photoluminescence properties of polycrystalline LaV1−xNbxO4 (x= 0--0.2) samples at room temperature. The substitution of Nb at the V site shows the fascinating structural and optical behavior due to their isoelectronic character and larger ionic radii of Nb5+ as compared to the V5+. The Rietveld refinement of x-ray diffraction patterns demonstrate that the x= 0 sample exist in a monoclinic (P21/n) phase, whereas for the x> 0, both monoclinic and scheelite-tetragonal (I41/a) phases co-exist in a certain proportion. Interestingly, a monotonous enhancement in the Raman spectral intensity with Nb substitution is correlated with the substitution induced increase in the scheelite-tetragonal phase. The x-ray absorption measurements reveal that the La ions exist in a trivalent oxidation state, while V and Nb cations possess 5+ oxidation state in tetrahedral coordination. Moreover, the Fourier-transform infrared (FTIR) spectra indicate that the Nb substitution give origin to some additional IR modes owing to the deformation of the VO43− tetrahedra and mixing of monoclinic and tetragonal phases. The photoluminescence measurements on these samples exhibit broadband spectra and their deconvolution designate the availability of more than one electron-hole pairs recombination center.
@article{arxiv.2102.02442,
title = {Structural phase transition and its consequences on optical behavior of LaV$_{1-x}$Nb$_x$O$_4$},
author = {Hemanshu Dua and Rishabh Shukla and R. S. Dhaka},
journal= {arXiv preprint arXiv:2102.02442},
year = {2021}
}