Synthesis of MnSb₂O₆ powders through a simple low-temperature method and their test as a gas sensor

In this work, a simple and economical chemical method was used to synthesize MnSb₂O₆ nanoparticles for their potential application as a gas sensor. The nanoparticles of the oxide were analyzed by powder X-ray diffraction, finding the crystalline phase at 600 °C. The crystallized oxide presented a hexagonal crystalline structure with spatial group P321. The microstructure of the material was analyzed by field-emission scanning electron microscopy, finding surface morphologies such as micro-plates, microspheres (diameter ~ 0.69 μm), and other particles without apparent shape. The average size of the nanoparticles was estimated at ~ 32.0 nm, according to images obtained by transmission electron microscopy (TEM). Oxidation states of the atomic elements forming the MnSb₂O₆ nanoparticles were found by X-ray photoelectron spectroscopy measurements. In the case of Mn, two oxidation states Mn²⁺ and Mn³⁺ corresponding to the Mn 2p_3/2 state were observed at 641.26 and 642.7 eV, respectively. For Sb, the Sb³⁺ oxidation state, associated with the Sb 3d_3/2 state, was located at 539.82 eV. The peak assigned to O at 530.82 eV overlaps the Sb 3d_5/2. The secondary ion mass spectrometry depth profiling showed a good distribution of the atomic elements in the nanoparticles, without additional elements or impurities. The optical properties were also studied by photoacoustic spectroscopy, revealing a direct transition of the MnSb₂O₆ nanoparticles with a band gap energy of 1.78 eV. The gas detection tests were performed in C₃H₈ and CO atmospheres at different concentrations and operating temperatures. The oxide showed an interesting behavior as the concentrations of the testing gases and the operating temperature increased. The high response presented by the MnSb₂O₆ suggests that this material can be used as a gas sensor.