Bi(x)La(1-x)VO4 solid solutions: tuning of electronic properties via stoichiometry modifications

• Published in: Nanoscale 2014-02, Vol.6 (4), p.2244-2254
• Main Authors: Kwolek, Przemysław, Pilarczyk, Kacper, Tokarski, Tomasz, Lewandowska, Kornelia, Szaciłowski, Konrad
• Format: Article
• Language: English
• Subjects: Bismuth - chemistry; Lanthanum - chemistry; Vanadates - chemistry
• ISSN: 2040-3372
• DOI: 10.1039/c3nr05871a

BixLa1-xVO4 solid solutions were obtained in the form of fine powder via a microwave-assisted hydrothermal route. The presence of a solid solution in the studied system was confirmed using X-ray diffraction (XRD) and optical spectroscopy techniques. Pure BiVO4 and LaVO4 were obtained in the monoclinic form, whereas solid solutions in the tetragonal, zircon-type structure. The optical band gap dependence on the composition of the solid solution is parabolic, thus there is a possibility to tune this parameter in a wide concentration range, from 2.4 to 4.0 eV. An absorption coefficient maximum is also concentration-dependent, possibly, due to the structural disorder of the samples. Solid solutions with Bi(3+) concentration between 11.94 and 32.57 at.% exhibit intense, green luminescence. This indicates the presence of Bi-originated electronic states within the band gap. The value of the conduction band edge potential, measured by both electrochemical impedance spectroscopy and work function measurements, is concentration-independent. Moreover, solid solutions exhibit a photoelectrochemical photocurrent switching effect, thus they may be promising materials for molecular electronics and as dioxygen activators.