Blue-shift of absorption edge in LaTiO2N by controlling the anion nonstoichiometry

✍ Scribed by Moriga, Toshihiro ;Aoki, Daisuke ;Nishida, Yasuhiro ;Kitaji, Kazuya ;Takahara, Keiko ;Murai, Kei-ichiro ;Nakabayashi, Ichiro

• Book ID: 105364025
• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 274 KB
• Volume: 203
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200669579

✦ Synopsis

Abstract

The perovskite‐type oxynitride LaTiO~2~N was prepared by heating an oxide precursor at 950 °C for 5 hours under NH~3~ atmosphere at a flow rate of 1 dm^3^/min. The precursor was prepared by the polymerized complex method. The oxynitride obtained was almost stoichiometric, LaTi(O~0.68~N~0.32~)~2.9~, with a reddish orange color. The oxynitride was successively annealed at 950 °C for 3 hours under a NH~3~ atmosphere at flow rates of 50 cm^3^/min, 30 cm^3^/min and 10 cm^3^/min, respectively. The color and composition varied from yellow LaTi(O~0.89~N~0.11~)~2.8~ through green‐yellow LaTi(O~0.93~N~0.07~)~2.9~ to light‐blue LaTi(O~0.98~N~0.02~)~2.9~ in accordance with the decreased flow rate. The absorption edges varied from 2.28 eV for the reddish orange, 2.56 eV for the yellow, 3.17 eV for the green‐yellow, to 3.44 eV for the light‐blue oxynitrides. Annealing under NH~3~ is therefore effective in color tuning, mainly resulting in a blue‐shift of the absorption edge. DV‐Xα calculations support the conclusion that the lower flow rate of NH~3~ led to a lower amount of nitrogen and higher oxygen levels in the oxynitrides. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)