Vanadate Inclusion Leading to Red-Ox-Rich Zircon PrCrO4: Synthesis, Magnetic, and Catalytic Properties

Abstract

Rare-earth-based ternary compounds with the formula REBO₄ (B = V, Cr, P, As) exhibit rich structural chemistry and associated technologically significant properties. Among the rare-earth chromates, realizing PrCrO₄ in a single polymorphic modification has been challenging. Herein, we report the successful stabilization of the zircon polymorph of PrCrO₄ by introducing 10 mol % of VO₄^3– instead of CrO₄^3– following a solution combustion method. Compositions with progressively higher amounts of vanadate have been synthesized and characterized extensively. XPS analysis of 10 and 50 mol % VO₄^3– substituted PrCrO₄ samples ascertained the existence of Pr^3+/4+, Cr^4+,5+, and V⁵⁺ in them, making it a red-ox-rich system. The tetragonal symmetry of PrCr_0.50V_0.50O₄ was confirmed from the HRTEM images and SAED patterns. FTIR and Raman spectral analyses indicated distorted tetrahedral (Cr/VO₄) units with a local site symmetry below D_2d. Both d-d and f-f transitions of Cr⁴⁺ and Pr³⁺, respectively, were observed in the absorption spectra. Field and temperature-dependent magnetic measurements of PrCr_0.50V_0.50O₄ confirmed its predominant paramagnetic behavior. The samples possessed porous morphology with a reasonable surface area. PrCr_1–xV_xO₄ (x = 0.00–0.50) samples catalyzed the oxidation of phenol. This study demonstrated B-site tuning in ABO₄ systems to select a desired polymorph preferentially.