Preparation of LaTiO₂N Using Hydrothermally Synthesized La₂Ti₂O₇ as a Precursor and Urea as a Nitriding Agent

Abstract

A facile method was successfully developed to prepare perovskite-type metal oxynitrides, LaTiO 2 N, from La 2 Ti 2 O 7 as a precursor in an atmosphere of N 2 . Urea was employed as a solid-state nitriding agent, instead of gaseous NH 3 , to increase the safety of the reaction. The hydrothermally prepared La 2 Ti 2 O 7 precursor had a nanosheet morphology and contained La(OH) 3 as a by-product. Through the optimization of reaction conditions including heat-treatment temperature and content [a]

Thermodynamic Stability and Anion Ordering of Perovskite Oxynitrides

“…Note that even plasma-cracked atomic nitrogen yields a N chemical potential of only Δμ N ≈ 1 eV/atom, which means it is highly improbable that an aqueous nitrogen precursor can attain the necessary N chemical potential required to form solid CaReO 2 N or CaReON 2 . However, solid LaTaON 2 might be synthesized in an aqueous environment, as Figure c indicates the stability of the solid PON at a N chemical potential of only Δμ N = −1 eV/atom, suggesting that the solid oxynitride might be synthesizable in the aqueous state using nitrogen-rich precursors such as urea, ammonia, hydrazine, or melamine. , Indeed, multiple experimental studies report successful laboratory synthesis of LaTaON 2 and LaTaO 2 N and confirm that this oxynitride does crystallize in a perovskite structure. , Despite the lack of established benchmarking for their aqueous chemical potentials, such precursors have demonstrated efficacy in the synthesis of other nitrides and oxynitrides, , suggesting their potential utility as precursors for the synthesis of PONs.…”

Thermodynamic Stability and Anion Ordering of Perovskite Oxynitrides

“…Figure 6a shows that the formation of CaReNO 2 is likely impossible in water, as CaReNO 2 can be stabilized only under conditions where the N chemical potential exceeds ≈ 3.2 eV/atom. Note that even plasma-cracked atomic nitrogen yields a N chemical potential of only +1 eV/atom, 52 which means it is highly improbable that an aqueous nitrogen precursor can attain the necessary N chemical potential required to form solid CaReO 2 N. However, solid LaTaON 2 might be synthesized in an aqueous environment, as Figure 6c indicates stability of the solid PON at a N chemical potential of only −1 eV/atom, suggesting that the solid oxynitride might be stable in the aqueous state using nitrogen-rich precursors such as urea, 53 ammonia, 54 hydrazine, 55 or melamine. 56,57 Indeed, multiple experimental studies report successful laboratory synthesis of LaTaON 2 or LaTaO 2 N and confirm that this oxynitride does crystallize in a perovskite structure.…”

Non-ammonolysis synthesis and characterisation of environmentally benign yellow pigments based on calcium–tantalum perovskite oxynitrides

“…This is presumably because of reduction of Ta 5+ in CaTa(O,N) 3 to Ta 4+ by urea, which also acts as a reducing agent. 40,41 In other words, the dull colour arose from a tantalum species, which was reduced during the urea-nitriding process. The Commission Internationale de l'Eclairage (CIE) L*a*b*Ch1 colour coordinate parameters of CaTa(O,N) 3 prepared using CaCO 3 (Ca : Ta : urea = 2 : 1 : 5) and Ca(OH) 2 (Ca : Ta : urea = 1.5 : 1 : 3) are summarised in Table 1.…”

“…[31][32][33][34][35][36][37][38] We recently developed a urea-nitriding method for synthesizing metal oxynitrides, namely GaN : ZnO and LaTiO 2 N, and the nitriding mechanisms were elucidated. 39,40 The shorter heat-treatment duration compared with those in processes that involve ammonolysis achieved a reduction in energy consumption and enabled the formation of finer sample powders. More recently, the strontium-tantalum oxynitride, SrTaO 2 N, and its solid solutions with Sr 1.4 Ta 0.6 O 2.9 have also been prepared by the urea-nitriding method using SrCO 3 and Ta 2 O 5 gel as precursors.…”