Molten nitrate eutectics: The reaction of four lanthanide chlorides

Habboush, D.A.; Kerridge, D.H.; Tariq, S.A.

doi:10.1016/0040-6031(83)80007-0

Cited by 16 publications

(8 citation statements)

References 11 publications

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“…A survey of the literature published on previous attempts to synthesize either of the two oxides, La 2 O 3 and Al 2 O 3 , LAP or similar aluminates by using MSS was not very encouraging. Thus, La(III) is a weak Lux‐Flood acid apparently existing in molten nitrates as a very stable lanthanyl cation LaO + (or La(OH) 2 + ) which is fairly inert and insoluble reacting only at high temperatures, or as La 2 O 3 which according to the Lux‐Flood theory is itself a base . Hence, lanthanum (III) chloride or hydrated lanthanum nitrate dissolves slowly in contact with molten nitrates to yield first a lanthanum oxide nitrate LaONO 3 and then on further heating at higher temperatures (~650°C) and almost simultaneously with the thermal decomposition of the nitrate flux, the corresponding La 2 O 3 oxide.…”

Section: Discussionmentioning

confidence: 99%

A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO₃ Nanoparticles in Molten Nitrates

et al. 2012

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Perovskite-type LaAlO 3 nanoparticles have been prepared by a facile, rapid, and environmentally friendly molten salts method using alkali metal nitrates as low-temperature fluxes. Starting from hydrated lanthanum and aluminum nitrates and alkali metal hydroxides, the proposed methodology consists briefly of two steps: a mechanically induced metathesis reaction followed by short firing at temperatures above nitrates melting points. The purpose of the first is twofold: on the one hand to generate in situ the alkali metal nitrate flux and on the other hand, to obtain a La and Al-containing precursor material suitable for the synthesis of bulk LaAlO 3 nanoparticles in molten nitrates. Different alkali metal nitrates and eutectic mixtures were used to analyze the influence of melt basicity in the reaction outcome. Single phase LaAlO 3 was obtained directly, without any purification step when using three molten media: LiNO 3 , NaNO 3 , and their mixture; using KNO 3 as flux either alone or as part of eutectic compositions, prevents complete conversion, and the title material is obtained mixed with additional crystalline phases such as lanthanum hydroxinitrates and carbonates. As-prepared LaAlO 3 powders are composed of loosely agglomerated nanoparticles with very fine crystallite size (32-45 nm). The present method reduces considerably previously reported synthesis time/temperatures for this material. D. Lupas-contributing editor Manuscript No. 30188.J ournal might well be useful to prepare other perovskite and garnettype complex oxides based on Ln 2 O 3 -Al 2 O 3 combinations (Ln: lanthanides and yttrium) for optical, electronic, and structural applications.

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Section: Discussionmentioning

confidence: 99%

A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO₃ Nanoparticles in Molten Nitrates

et al. 2012

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“…It has been reported6 that the solid product when cobalt(I1) chloride is heated up to 600 "C with the eutectic is tricobalt tetraoxide, equation (2). However the simpler Lux-Flood acidbase l 7 reaction (3) presumably took place at lower temperatures, CoCl, + C03,-+ COO + CO, + 2Cl- (3) with progressive oxidation of the cobalt(I1) oxide as the temperature increased, becoming complete by 600 "C. The dilute lilac solution gave a spectrum with a band at 17 000 cm-' ( E = 85 f 10 dm3 mol-' cm-') and a shoulder at 19 000 cm-' (E = 73.5 k 8.5 dm3 mol-' cm-'). Reflectance spectra of the lilac solids obtained by quenching the lilac solutions also showed a band at ca.…”

Section: Resultsmentioning

confidence: 99%

“…The surprising fact that first-row transition metal compounds generally can form stable coloured solutions in a molten ternary carbonate eutectic has however not been apparent from the literature, as until now the only reference has been to nickel(I1) solutions. 6 Indeed until now it was generally presumed that transition metal cations would be too acidic to have more than a transitory existence in the highly basic carbonate melt.…”

mentioning

confidence: 99%

Molten lithium carbonate–sodium carbonate–potassium carbonate eutectic: electronic spectroscopy of first-row transition metal compounds

Carthey¹,

Kerridge²

1987

J. Chem. Soc., Dalton Trans.

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Stable solutions containing chromate(vi), cobalt(ii), nickel(ii), and copper(ii) have been obtained at 420 "C in a molten lithium carbonate-sodium carbonate-potassium carbonate eutectic. Electronic spectroscopy has demonstrated the existence of the tetrahedral chromate(vi) in the melt while nickel(i1) and copper(ii) exhibited six-fold co-ordination by oxygen, the nickel(ii) species appearing to change to a more symmetrical octahedral co-ordination on solidification. The cobalt( ii) geometry can be interpreted as octahedral or dodecahedral. While chromate(vi) dissolved readily in the melt without apparent decomposition, attempts to prepare more concentrated solutions ( >0.01 mol kg-l) of the acidic cobalt(ii), nickel(ii), or copper(ii) cations resulted in the precipitation of the respective metal oxide due to acid-base reactions with the carbonate ion.

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“…(or La(OH) 2 ? ) [19,33,34], aluminium is as a very strong L-F acid which depending on the nature of the precursor salt and basicity of the melt, might precipitate as Al 2 O 3 or remain dissolved as an oxonanion AlO 2 - [35,36]. There are two prevailing mechanisms shaping multicomponent phase formation in molten salts which are generally known as ''template formation'' and ''dissolution-precipitation''; in the first one, the more soluble reactant dissolves in the flux, diffuses to the surface of the less-soluble component and reacts to give a mixed compound.…”

Section: Reaction Mechanismmentioning

confidence: 98%

Molten salts synthesis and electrical properties of Sr- and/or Mg-doped perovskite-type LaAlO3 powders

et al. 2012

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Lanthanum-based LaBO 3 oxides adopting the very stable perovskite structure are currently considered attractive materials for a growing number of applications in the field of solid-state ionics. In particular, LaAlO 3 -based perovskites are promising electrolyte materials for solid oxide fuel cells because they show almost pure oxygen ion conductivity at low oxygen partial pressures and high temperatures as well as excellent thermal and chemical stability under the standard operating conditions. This article describes a low-temperature synthesis of pure and acceptordoped perovskite-type LaAlO 3 nanopowders via a facile and environmental-friendly molten salts method. Using hydrated metal nitrates and sodium hydroxide as raw materials, the proposed methodology consists of two steps: a mechanically induced metathesis reaction and short firing above NaNO 3 's melting point. The purpose of the first is twofold: i.e., to generate in situ the NaNO 3 flux and to obtain a suitable precursor for the synthesis of the target materials in molten nitrates. Accordingly, pure and Mg-and/or Sr-doped LaAlO 3 powders were obtained directly without using any purification step at temperatures B500°C. When preparing the Mg-containing samples, NaNO 2 was also added to the reaction mixture to increase melt reactivity. The formation of the target series in the molten salt is thought to proceed through a ''dissolution-precipitation'' mechanism with LaAlO 3 particles precipitating during cooling from a solution oversaturated with reactants. Electrical properties of the as-prepared materials were measured as a function of temperature and frequency by means of impedance spectroscopy and found comparable to those shown by similar materials prepared using more complicated routes.

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Molten nitrate eutectics: The reaction of four lanthanide chlorides

Cited by 16 publications

References 11 publications

A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO₃ Nanoparticles in Molten Nitrates

A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO₃ Nanoparticles in Molten Nitrates

Molten lithium carbonate–sodium carbonate–potassium carbonate eutectic: electronic spectroscopy of first-row transition metal compounds

Molten salts synthesis and electrical properties of Sr- and/or Mg-doped perovskite-type LaAlO3 powders

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Molten nitrate eutectics: The reaction of four lanthanide chlorides

Cited by 16 publications

References 11 publications

A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO3 Nanoparticles in Molten Nitrates

A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO3 Nanoparticles in Molten Nitrates

Molten lithium carbonate–sodium carbonate–potassium carbonate eutectic: electronic spectroscopy of first-row transition metal compounds

Molten salts synthesis and electrical properties of Sr- and/or Mg-doped perovskite-type LaAlO3 powders

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A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO₃ Nanoparticles in Molten Nitrates

A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO₃ Nanoparticles in Molten Nitrates