Fundamental study of LaMg x Cr1−x O3−δ perovskites nano-photocatalysts: Sol-gel synthesis, characterization and humidity sensing

Abstract

Nanocrystalline perovskite oxides, LaMgxCr1−xO3−δ (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1) were prepared by sol-gel method. The samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and nitrogen adsorption/desorption isotherms at 77 K, respectively, to identify the structural phases, surface morphology, vibrational stretching frequencies and BET surface area of the samples. Also, it was investigated the humidity sensing characteristics of the samples. The composites were sintered at 800 °C for 5 h and subjected to dc electrical conductivity studies at room temperature. The resistance measurements as a function of relative humidity (RH) in the range of 5-98% were done and the humidity sensing factors (Sf =R5%/R98%) calculated. The activation energy of the compounds were determined from the temperature-dependent electrical conductance experiments in the temperature range of 120-300 °C. LaMgCr-3 (x=0.4) had the highest humidity sensing factor 21407±431, while LaCr-1 (x=0) the lowest sensitivity factor 27.27±2. The response and recovery characteristics were studied for LaMgCr-3, which exhibited good linearity and a very narrow hysteresis loop. The photocatalytic activity of LaMgxCr1−xO3−δ was investigated by using the photo-decomposition of 4-chlorophenol (4-CP) under UV-visible light. The sample LaMgCr-3 (x=0.4) showed the highest photocatalytic degradation efficiency (93.05%) than other samples, due to their smaller size of particles with higher surface area.