Synthesis of BaTaO₂N Powders Utilizing NH₃ Decomposition

Abstract

The current methodology for perovskite oxynitride synthesis is a gas-solid reaction with ammonia. However, a competing reaction exists, where ammonia dissociates to inert N 2 , rather than a nascent, active nitriding species. Therefore, oxynitride synthesis is controlled by the composition of the gas phase. Control of key processing variables (temperature, flow velocity, sample placement, temperature distribution, furnace configuration) determines the gas-phase components (NH 3 , N 2 , and H 2 ) and subsequently, the reaction rate and purity of BaTaO 2 N powders.E. Suvaci-contributing editor

Synthesis of Nanostructured BaTaO2N Thin Films as Photoanodes for Solar Water Splitting

“…In addition, Ta 2 N was observed as a result of a phase transformation from Ta 4 N 5 via Ta 5 N 6 and ε-TaN and diffusion of metallic Ta from the substrate. The interaction of abundant NH and NH 2 radicals with planar Ba 5 Ta 4 O 15 and Ta metal could complicate the nitridation process, although the quality of BaTaO 2 N powder was reported to increase with NH 3 flow rate . Therefore, it is important to carefully optimize the nitridation conditions for Ba 5 Ta 4 O 15 nanosheet films on Ta substrates to synthesize high-purity BaTaO 2 N films.…”

A review of metal oxynitrides for photocatalysis

“…22 The key parameters for the ammonolysis reaction are temperature, nitrogen flow rate; reaction time and sample placement in the reaction tube and the gas composition (NH 3 , N 2 and H 2 ) around the sample should be considered to optimize the purity of the oxynitride phase. 23 Ammonia acts as a reducing and an oxidizing (nitriding) agent, this dual behavior nitriding and reducing is essential for the ammonolysis reaction.…”

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“…Ammonolysis reactions are used starting with precursor oxides or mixtures of binary oxides, nitrides and carbonates. 11 The reducing power of NH 3 together with the presence of H 2 makes more difficult the stabilization of ionocovalent oxynitrides of the metals more electronegative (e.g. 2a).…”

“…The key parameters of temperature, flow rate, time and sample placement in the reaction tube among other factors determine the gas composition (NH 3 , N 2 and H 2 ) around the sample and should be considered to optimize the purity of the oxynitride phase. 11 The reducing power of NH 3 together with the presence of H 2 makes more difficult the stabilization of ionocovalent oxynitrides of the metals more electronegative (e.g. late transition metals) which form interstitial nitrides with the cations in low oxidation states.…”