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A “Green Chemistry” Approach to the Synthesis of Rare‐Earth Aluminates: Perovskite‐Type LaAlO 3 Nanoparticles in Molten Nitrates
Author(s) -
MendozaMendoza Esmeralda,
Montemayor Sagrario M.,
EscalanteGarcía José I.,
Fuentes Antonio F.
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2011.05043.x
Subject(s) - eutectic system , alkali metal , lanthanum , nanoparticle , perovskite (structure) , chemical engineering , inorganic chemistry , phase (matter) , alkaline earth metal , lanthanide , molten salt , chemistry , crystallite , materials science , metal , mineralogy , nanotechnology , microstructure , metallurgy , crystallography , organic chemistry , engineering , ion
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.