Effect of terbium doping on structural, optical and gas sensing properties of In2O3 nanoparticles

In this work, the effect of terbium (Tb3+) as dopant on the structural, optical, electrical and gas sensing properties of In2O3 (indium oxide) nanoparticles has been discussed. In2O3 and Tb3+-doped In2O3 nanoparticles were synthesized by a facile and cost effective co-precipitation method. XRD analysis revealed the formation of bixbyite-type cubic phase for In2O3 and Tb3+-doped In2O3 nanoparticles which was further supported by Raman studies. It was observed that the crystallite size of In2O3 nanoparticles decreased, while structural disorder increased with increase in Tb3+ concentration. SEM micrographs showed that particles were spherical in shape and EDS corroborated the presence of Tb3+ in doped In2O3 nanoparticles. A broadening and shifting of Raman peaks with increase in Tb3+ content was also observed. For gas sensing characteristics, the nanoparticles were applied as thick film onto the alumina substrate and tested at different operating temperatures for various volatile organic compounds (such as methanol, ethanol, acetone) and ammonia. The results indicated that the sensor based on 5%Tb3+-doped In2O3 nanoparticles presented much higher sensor response to 50ppm ethanol at 300 °C temperature than the pure In2O3 sensor. The enhancement of the response may be attributed to high surface basicity, small size and large lattice distortion of doped In2O3 sensor.