Zn₂BO₄:N (B = Ti, Sn) spinels obtained by the Pechini method, with N-doping by plasma processing

Full text: Oxides with spinel structure may be applied as humidity sensors, gas sensors, anodes for lithium battery, ceramic pigments, photoluminescent materials and photocatalysts. In this work, Zn₂Sn_1-xTi_xO₄ (x = 0,0; 1,0) spinels were synthesized by the Pechini method, doped with N by nitridation using plasma at different temperatures and times. Catalysts were characterized by X-ray diffraction, UV-vis spectroscopy and infrared spectroscopy. Single phase zinc stannate (Zn₂SnO₄) was obtained after nitridation, while ZnO with wurtzite structure was found after zinc titanate (Zn₂TiO₄) nitridation. Moreover, a small shift of the peaks was observed after nitridation. When nitridation of amorphous materials was performed at 400 oC, low intensity peaks were observed indicating that a low crystallinity was attained. The band gap energies of the Zn₂SnO₄ and Zn₂TiO₄ after calcination at 900°C and after nitridation were 3.32 - 3.45 eV and 3.45 - 3.69 eV, respectively. Different behaviors were observed for the two spinels, while Zn₂SnO₄ presented a decrease of the band gap after nitridation, Zn₂TiO₄ presented an increase. Moreover both materials presented electronic transitions at the low energy part of the spectra. IR spectra showed bands assigned to metal-oxygen bond in octahedral (SnO₆ and/or TiO₆ and ZnO₆) and tetrahedral sites [ZnO₄], besides very weak bands assigned to nitrogen bonds, after nitridation. (author)