Partial nitrogen loss in SrTaO2N and LaTiO2N oxynitride perovskites

• Published in: Solid state sciences Vol. 54; pp. 2 - 6
• Main Authors: Chen, Daixi, Habu, Daiki, Masubuchi, Yuji, Torii, Shuki, Kamiyama, Takashi, Kikkawa, Shinichi
• Format: Journal Article
• Language: English
• Published: Elsevier Masson SAS 01-04-2016
• Subjects: Atmospheres; Color; Crystal structure; Decomposition; Lattices; N-type semiconductors; Oxynitride; Oxynitrides; Perovskite; Perovskites; Thermal stability; Titanium dioxide; Perovskite; Thermal stability; Oxynitride; Crystal structure
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2015.08.018

SrTaO2N heated in a helium atmosphere began to release nitrogen of approximately 30 at% at 950 °C while maintaining the perovskite structure and its color changed from orange to dark green. Then it decomposed above 1200 °C to a black mixture of Sr1.4Ta0.6O2.73, Ta2N, and Sr5Ta4O15. The second decomposition was not clearly observed when SrTaO2N was heated in a nitrogen atmosphere below 1550 °C. After heating at 1500 °C for 3 h under a 0.2 MPa nitrogen atmosphere, the perovskite product became dark green and conductive. Structure refinement results suggested that the product was a mixture of tetragonal and cubic perovskites with a decreased ordering of N3−/O2−. The sintered body was changed to an n-type semiconductor after a partial loss of nitrogen to be reduced from the originally insulating SrTaO2N perovskite lattice. LaTiO2N was confirmed to have a similar cis-configuration of the TiO4N2 octahedron as that of TaO4N2 in SrTaO2N. It also released some of its nitrogen at 800 °C changing its color from brown to black and then decomposed to a mixture of LaTiO3, La2O3, and TiN at 1100 °C. These temperatures are lower than those in SrTaO2N.
Orange SrTaO2N and dark green SrTaO2N0.7 powder samples. [Display omitted]
•Thermal behavior was studied on SrTaO2N and LaTiO2N oxynitrides in helium flow.•Partially nitrogen lost perovskites were found during their decomposition.•Crystal structure and electrical property were studied on the SrTaO2N0.7 intermediate.•Cis-configuration was found in the TiO4N2 octahedron of LaTiO2N.