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A study on the thermal conversion of scheelite-type ABO4 into perovskite-type AB(O,N)3

Li, Wenjie and Li, Duan and Gao, Xin and Gurlo, Aleksander and Zander, Stefan and Jones, Philip and Navrotsky, Alexandra and Shen, Zhijian and Riedel, Ralf and Ionescu, Emanuel (2015):
A study on the thermal conversion of scheelite-type ABO4 into perovskite-type AB(O,N)3.
In: Dalton Trans., 44 (17), pp. 8238-8246. The Royal Society of Chemistry, ISSN 1477-9226,
[Article]

Abstract

Phase-pure scheelite AMoO(4) and AWO(4) (A = Ba, Sr, Ca) were thermally treated under an ammonia atmosphere at 400 to 900 degrees C. SrMoO4 and SrWO4 were shown to convert into cubic perovskite SrMoO2N and SrWO1.5N1.5, at 700 degrees C and 900 degrees C respectively, and to form metastable intermediate phases (scheelite SrMoO4-xNx and SrWO4-xNx), as revealed by X-ray diffraction (XRD), elemental analysis and FTIR spectroscopy. High-temperature oxide melt solution calorimetry reveals that the enthalpy of formation for SrM(O,N)(3) (M = Mo, W) perovskites is less negative than that of the corresponding scheelite oxides, though the conversion of the scheelite oxides into perovskite oxynitrides is thermodynamically favorable at moderate temperatures. The reaction of BaMO4 with ammonia leads to the formation of rhombohedral Ba3M2(O,N)(8) and the corresponding binary metal nitrides Mo3N2 and W4.6N4; similar behavior was observed for CaMO4, which converted upon ammonolysis into individual oxides and nitrides. Thus, BaMO4 and CaMO4 were shown to not provide access to perovskite oxynitrides. The influence of the starting scheelite oxide precursor, the structure distortion and the degree of covalency of the B-site-N bond are discussed within the context of the formability of perovskite oxynitrides.

Item Type: Article
Erschienen: 2015
Creators: Li, Wenjie and Li, Duan and Gao, Xin and Gurlo, Aleksander and Zander, Stefan and Jones, Philip and Navrotsky, Alexandra and Shen, Zhijian and Riedel, Ralf and Ionescu, Emanuel
Title: A study on the thermal conversion of scheelite-type ABO4 into perovskite-type AB(O,N)3
Language: English
Abstract:

Phase-pure scheelite AMoO(4) and AWO(4) (A = Ba, Sr, Ca) were thermally treated under an ammonia atmosphere at 400 to 900 degrees C. SrMoO4 and SrWO4 were shown to convert into cubic perovskite SrMoO2N and SrWO1.5N1.5, at 700 degrees C and 900 degrees C respectively, and to form metastable intermediate phases (scheelite SrMoO4-xNx and SrWO4-xNx), as revealed by X-ray diffraction (XRD), elemental analysis and FTIR spectroscopy. High-temperature oxide melt solution calorimetry reveals that the enthalpy of formation for SrM(O,N)(3) (M = Mo, W) perovskites is less negative than that of the corresponding scheelite oxides, though the conversion of the scheelite oxides into perovskite oxynitrides is thermodynamically favorable at moderate temperatures. The reaction of BaMO4 with ammonia leads to the formation of rhombohedral Ba3M2(O,N)(8) and the corresponding binary metal nitrides Mo3N2 and W4.6N4; similar behavior was observed for CaMO4, which converted upon ammonolysis into individual oxides and nitrides. Thus, BaMO4 and CaMO4 were shown to not provide access to perovskite oxynitrides. The influence of the starting scheelite oxide precursor, the structure distortion and the degree of covalency of the B-site-N bond are discussed within the context of the formability of perovskite oxynitrides.

Journal or Publication Title: Dalton Trans.
Journal volume: 44
Number: 17
Publisher: The Royal Society of Chemistry
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
Date Deposited: 22 Feb 2016 11:57
Official URL: http://dx.doi.org/10.1039/c5dt00711a
Identification Number: doi:10.1039/c5dt00711a
Funders: This research was funded by the European Union Seventh Framework Programme (FP7/2007-2013) under the grant agreement FUNEA - Functional Nitrides for Energy Applications., The calorimetry at UC Davis was supported by the U.S. Dept. of Energy, Office of Basic Energy Sciences, grant DE-FG02-03ER46053.
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