Consequences of Bi3+ introduction for Pr3+ in PrAlO3

Abstract

With the intent to comprehend the structure and hence the property changes in the PrAlO3 system, the substitution of Bi3+ for Pr3+ has been attempted. The samples were synthesized by solution combustion synthesis and characterized extensively. X-ray diffraction studies revealed that the rhombohedral perovskite structure was preserved up to 20 mol% substitution of bismuth, beyond which diffraction peaks of the secondary phase of α-Bi2O3emerged. The structural refinements indicated the increment of both a and c lattice dimensions with an increase in bismuth content. The samples had porous morphology, and a mean pore diameter of 22.4 nm, along with a surface area of 100 m2/g, was deduced from BET measurements for the 20 mol% bismuth-substituted sample. FTIR, Raman spectroscopic and electron microscopic analysis reinforced the perovskite structure adopted by the bismuth-substituted samples. Both Pr and Bi in Pr0.80Bi0.20AlO3 existed in the + 3 oxidation state as established from the XPS analysis. The inclusion of bismuth introduced intermediate energy levels within the bandgap, as suggested by the redshift of the absorption edge for the bismuth-substituted samples. As the optical bandgap values were in the semiconductor regime, the application of bismuth-replaced samples as a catalyst for the photodegradation of crystal violet dye solution was demonstrated. The amount of dye degraded increased with an increase in the amount of bismuth in the sample. Additionally, Pr0.80Bi0.20AlO3 catalyzed the reduction of nitroaromatics promoted possibly by the Bi3+/Bi(0) redox couple.