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

• Published in: Physica status solidi. A, Applications and materials science Vol. 203; no. 11; pp. 2818 - 2822
• Main Authors: Moriga, Toshihiro, Aoki, Daisuke, Nishida, Yasuhiro, Kitaji, Kazuya, Takahara, Keiko, Murai, Kei-ichiro, Nakabayashi, Ichiro
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.09.2006; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: 72.80.Ga; 81.40.Tv; Exact sciences and technology; Physics; Annealing; Spectral line shift; Heat treatments; Nonstoichiometry; Color; Absorption edge
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.200669579

The perovskite‐type oxynitride LaTiO2N was prepared by heating an oxide precursor at 950 °C for 5 hours under NH3 atmosphere at a flow rate of 1 dm3/min. The precursor was prepared by the polymerized complex method. The oxynitride obtained was almost stoichiometric, LaTi(O0.68N0.32)2.9, with a reddish orange color. The oxynitride was successively annealed at 950 °C for 3 hours under a NH3 atmosphere at flow rates of 50 cm3/min, 30 cm3/min and 10 cm3/min, respectively. The color and composition varied from yellow LaTi(O0.89N0.11)2.8 through green‐yellow LaTi(O0.93N0.07)2.9 to light‐blue LaTi(O0.98N0.02)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 NH3 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 NH3 led to a lower amount of nitrogen and higher oxygen levels in the oxynitrides. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)