Structural and optical properties of perovskite-type LaTiO2N synthesized using urea or thiourea as co-nitriding agents

摘要

Perovskite-type LaTiO2N powders were successfully synthesized by thermal ammonolysis of La2Ti2O7 at 950 degrees C in the presence of urea or thiourea as co-nitriding agents. The products formed at different La2Ti2O7:urea or La2Ti2O7:thiourea mass ratios were systematically characterized by SEM, XRD, particle size distribution analysis, BET, UV vis, XPS and O/N analysis. Results show that the addition of urea is highly beneficial for LaTiO2N synthesis, yielding pure phase products with a higher nitrogen content than LaTiO2N powders prepared in the absence of urea. Conversely, the addition of thiourea was detrimental to the structural and optical properties of LaTiO2N, due to the formation of La2O2S as a side-product. La2O2S formation resulted in a sub-stoichiometric La:Ti ratio in the LaTiO2N products, which dramatically lowered the reflectivity of the product powders above the absorption edge due to excess bulk Ti3+ centres. Urea or thiourea addition also decreased the median particle size of the LaTiO2N powders. (C) 2015 Elsevier Ltd. All rights reserved.