Consequences of Bi 3+ introduction for Pr 3+ in PrAlO 3
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Consequences of Bi3+ introduction for Pr3+ in PrAlO3 Vipul Shrivastava1 and Rajamani Nagarajan1,* 1
Materials Chemistry Group, Department of Chemistry, University of Delhi, New Delhi 110007, India
Received: 22 June 2020
ABSTRACT
Accepted: 12 August 2020
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 a-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.
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https://doi.org/10.1007/s10853-020-05106-3
J Mater Sci
GRAPHIC ABSTRACT
Introduction The technological significance of perovskite-structured oxides with the general formula of ABO3 invites the attention of researchers of diverse fields [1–6]. Rare earth orthoaluminates (REAlO3) are recognized as next-generation scintillator materials in addition to their useful applications as neutron absorbers, flux suppressors and container materials involving high-temperature processes [2, 7–21]. PrAlO3 stands out from the rest of the rare earth aluminates in terms of temperature-dependent structural phase transitions as well as the magnetic field-induced reorientation of the crystallographic axes [9, 14, 22]. PrAlO3 crystallizes in a hexagonal crystal system with rhombohedral symmetry (R-3c space group) at ambient conditions. It transforms into other phases involving the rotation or tilting of AlO6 octahedra coupled with the magnetic ordering of the Pr-ion at high and low temperatures [18, 22]. The narrowband 4f–4f and broadband 5d–4f emission present in Pr3? qualifies PrA
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