Ni2As2O7 pyrochlore nanomaterial: Solid state synthesis, crystal structure determination, crystal phase growth study and physical properties

Nanostructured Ni2As2O7 semiconductor samples were synthesized by a solid state method among As2O3 and Ni(NO3)2.6H2O raw materials at 650 °C (S1) and 750 °C (S2) as reaction temperatures. The synthesized nanomaterials were characterized by powder X-ray diffraction (PXRD) technique and Fourier-transform infrared (FTIR) spectroscopy. The Rietveld analysis showed that the obtained materials were crystallized well in the triclinic crystal structure with the space group P1. The data of Rietveld analysis showed that the purity of the synthesized nanomaterials was increased by increasing the reaction temperature. The morphologies of the synthesized materials were studied by field emission scanning electron microscope (FESEM). It was found that the morphology of the obtained materials was changed from homogeneous sponge to particles and somewhat porous structure, by increasing the reaction temperature. Besides, the average particle sizes were increased considerably by increasing the reaction temperature. Ultraviolet-visible spectra analysis showed that the synthesized Ni2As2O7 nanomaterials had strong light absorption in the ultraviolet light region. The direct optical band gap energies were 3.20, 3.90, 4.80 eV and 2.9, 3.40, 4.70 eV for S1 and S2, respectively. The data showed that the band gaps were decreased by increasing the reaction temperature that can be due to the increasing the crystallite sizes of the targets.