Abstract
Considering the absence of reports dealing with the perovskite-structured orthochromites containing two A-site magnetic rare-earth ions, GdCrO3 and progressively Dy3+-substituted samples of the series Gd1-x Dy x CrO3 have been synthesized employing the epoxide-mediated sol-gel procedure. The samples were characterized extensively using high-resolution powder X-ray diffraction, thermal analysis, Fourier transform infrared, Raman, and UV-visible spectroscopies, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) measurements. Monophasic samples possessing an orthorhombic perovskite structure emerged by calcining the xerogels formed by the reaction of rare-earth nitrates, chromium(III)chloride, and propylene oxide at 800 °C for 2 h. Uniform presence of wormlike morphology was observed in both the field emission SEM (FE-SEM) and TEM images of the samples. Zero-field and field-cooled magnetic measurements using a SQUID magnetometer down to 4 K showed that the Neel temperature of Gd0.5Dy0.5CrO3 was 155 K, more or less midway between the values observed for GdCrO3(169 K) and DyCrO3 (146 K). For the Gd0.5Dy0.5CrO3 sample, a spin reorientation was observed at ∼38 K when measured under an applied field. Because the optical band gap, determined by Kubelka-Munk function, of these chromites was around 3 eV, their application as a catalyst for the photodegradation of the aqueous rhodamine-6G dye solution was demonstrated, in which the percentage of the total dye that was degraded varied with the average ionic radius of A-site ions. A similar systematic trend was observed even for the catalytic oxidation of the XO dye in the presence of H2O2, with DyCrO3 influencing the reaction to a greater extent followed by Gd0.5Dy0.5CrO3 and GdCrO3. Both the photocatalytic and catalytic reactions followed pseudo-first-order kinetics.