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Synthesis and Dielectric Properties of Thin-Layered (La,Nd)TiO2N Perovskites
J. Ahchawarattaworn1, D.P. Thompson1, F. Azough2, R. Freer2
1 School of Chemical Engineering and Advanced Materials, University of Newcastle, Newcastle upon Tyne, NE1 7RU, U.K.
2 School of Materials, University of Manchester, Manchester M13 9PL, U.K.
received June 3, 2015, received in revised form August 28, 2015, accepted October 5, 2015
Vol. 7, No. 1, Pages 39-46 DOI: 10.4416/JCST2015-00022
Abstract
Dielectric measurements made on thin layers of oxynitride of composition (La,Nd)TiO2N deposited on substrates of the equivalent pure oxides gave high and variables values for the relative permittivity, and very high values of dielectric loss, showing that the samples were significantly conducting. This is believed to be due to reduction taking place during the nitridation step, the use of ammonia (by far the most convenient and effective nitriding agent for this purpose) resulting in the simultaneous production of active atomic hydrogen which easily diffuses through both the surface oxide and the simultaneously forming layer of oxynitride to give compositions of the type (La,Nd)2TiIV2-xTiIIIxO7-x/2 and LaxNd1-xTi4+1-yTi3+yO2-y/2N respectively. It is well established that the presence of Ti3+ in titanium oxides and oxynitrides readily promotes conductivity. These results explain the diverse dielectric property measurements reported by previous researchers working on oxynitride materials, and show that alternative nitridation methods are needed in order to determine correct values of dielectric properties of pure oxynitride materials.
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Keywords
Oxynitrides, perovskites, XRD characterisation, dielectric properties.
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