Structural and optical properties of perovskite-type LaTiO2N synthesized using urea or thiourea as co-nitriding agents
Structural and optical properties of perovskite-type LaTiO2N synthesized using urea or thiourea as co-nitriding agents
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DOI：
10.1016/j.jeurceramsoc.2015.02.019
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发表时间：
2015-10
影响因子：
5.7
通讯作者：
Narendra G. Sarda;Minami Omune;Takanori Hayashi;A. Chan;S. Kataoka;K. Murai;Geoffrey I N Waterhouse;T. Moriga
中科院分区：
文献类型：
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作者：
Narendra G. Sarda;Minami Omune;Takanori Hayashi;A. Chan;S. Kataoka;K. Murai;Geoffrey I N Waterhouse;T. Moriga
以La 2 Ti 2 O 7为原料，尿素或硫脲为共氮化剂，在950 °C下热氨解合成了钙钛矿型LaTiO 2N粉体。采用SEM、XRD、粒度分布分析、BET、UV-vis、XPS和O/N分析等手段对不同La 2 Ti 2 O 7：尿素和La 2 Ti 2 O 7：硫脲质量比下生成的产物进行了系统的表征。结果表明，尿素的加入是非常有益的LaTiO 2 N合成，产生纯相产品具有更高的氮含量比在没有尿素的情况下制备的LaTiO 2 N粉末。相反，硫脲的加入是有害的结构和光学性能的LaTiO 2 N，由于形成的La 2 O 2 S作为副产物。La 2 O2 S的形成导致在LaTiO 2N产品中的亚化学计量的La：Ti比率，这由于过量的体Ti 3+中心而显著降低了产品粉末在吸收限以上的反射率。尿素或硫脲添加也降低了LaTiO 2 N粉末的中值粒径。
Perovskite-type LaTiO2N powders were successfully synthesized by thermal ammonolysis of La2Ti2O7at 950 °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.