Synthesis, characterization of NdCoO3 perovskite and its uses as humidity sensor

The perovskite NdCoO3 nanoparticles were prepared by the citrate auto combustion method. The synthesized powders were characterized by XRD, HRTEM, EDAX, and AFM analyses. The XRD pattern of NdCoO3 confirms the orthorhombic perovskite structure with an average crystallite size of 14.46 nm. The EDAX data indicate that the precursors have fully undergone the chemical reaction to form the predictable composition of the investigated sample. The magnetic hysteresis properties were carried out at room temperature and 100 K. At low temperature, the coericivity of the investigated samples is approximately equal to 22.644 G which is approximately 2.5 greater than its value at room temperature. The investigated sample shows paramagnetic behavior at both temperatures. This behavior can be attributed to the change of electron configurations and ligand field states. The ferroelectric nature was identified by taking the P-E loops at various applied voltages. The spin state of cobalt ions plays an important role in the magnetic properties and humidity-sensing behavior. The humidity-sensing behavior of the prepared sample was studied in a wide range of working humidity (11-97% RH) and testing frequency (100 Hz-100 kHz). The proposed humidity sensor was evaluated in terms of hysteresis, repeatability, and recovery time. Based on the obtained data the optimum testing frequency was chosen to be 100 Hz. The proposed sensor shows a very fast response of 3 s for low humidity. The humidity sensor exhibits good sensitivity over a middle RH range (11-43%).