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Perovskite-type oxynitride dielectrics

Lookup NU author(s): Jeng Ahchawarattaworn, Dr Alasdair Charles, Emeritus Professor Derek Thompson


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The rare earth oxynitrides LaTiO2N and NdTiO2N have been synthesised by ammonolysis of complex oxide precursors, prepared by solid-state reaction between appropriate binary oxide powders. La 2Ti2O7 and Nd2Ti2O 7 were prepared by reaction of La2O3 and TiO2, and Nd2O3 and TiO2, respectively in a 1:2 molar ratio. The products were heated in ammonia gas at 950°C for several hours, with intermediate regrinding. By XRD, it was found that almost pure LaTiO2N had been obtained after 24 hours reaction time with less than 5% TiN as the only impurity, while NdTiO2N needed more than 24 hours to obtain the pure phase. To densify the samples, they were hot-pressed in graphite dies at 1250°C, 25 bars for 1 hour and whereas LaTiO2N remained unchanged, the NdTiO2N sample decomposed. Dielectric property investigations showed that the LaTiO2N sample showed metallic rather than dielectric behaviour due to the conductivity of TiN. To further improve the purity, La2Ti2O7 was again treated by ammonolysis at 950°C for 16 hours with 10 wt% carbon powder added to the mix. XRD showed that pure LaTiO2N had been obtained. Further work is in progress to determine dielectric properties of this and related oxynitride materials as a function of voltage, temperature and frequency so that the values can be compared with those of equivalent oxide materials. Dense samples of other Ti - and Ta-based perovskite oxynitrides are also currently being developed.

Publication metadata

Author(s): Ahchawarattaworn J, Charles E, Thompson D, Freer R

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: The Minerals, Metals and Materials Society: 3rd International Conference on Processing Materials for Properties (PMP III)

Year of Conference: 2009

Pages: 980-985

Publisher: The Minerals, Metals & Materials Society (TMS)

Library holdings: Search Newcastle University Library for this item

ISBN: 9781615674237