Yttrium Aluminum Garnet Nanopowders Produced by Liquid-Feed Flame Spray Pyrolysis (LF-FSP) of Metalloorganic Precursors

Abstract

We report here the synthesis of yttrium-aluminum garnet oxide (Y 3 Al 5 O 12 ) nanopowders by liquid-feed flame spray pyrolysis (LF-FSP) of combinations of yttrium and aluminum precursors dissolved in EtOH, n BuOH, and/or THF. These include solutions of the following: yttrium and aluminum nitrates in EtOH or n BuOH; yttrium 2-ethylhexanoate and alumatrane [N(CH 2 CH 2 O) 3 Al] in THF or EtOH; yttrium methoxyacetate and alumatrane in EtOH; yttrium acetylacetonate and alumatrane in EtOH, and yttrium propionate and aluminum acetylacetonate in EtOH or THF. Each precursor system was aerosolized with O 2 and subsequently ignited. Following combustion, the resulting powders were collected by electrostatic precipitation at rates of 50 g/h. Surprisingly, the precursor choice strongly influences both the initial phase composition and morphology of the LF-FSP powder, as well as the phase changes that occur during annealing. As-collected LF-FSP nanopowders, average particle size (APS) e100 nm, had the YAG composition of the precursor feed; but XRD shows an apparent mixture of hexagonal YAlO 3 I and some Y 4 Al 2 O 9 (YAM). The remaining Al 2 O 3 exists either as nanosegregated, amorphous alumina or in defect structures. However, the most homogeneous powders exhibit FTIR, TGA/DTA, TEM, and XRD data that suggest a new phase with a modified YAlO 3 I crystal structure and a YAG composition. Powders annealed at 900-1000 °C (7-10 d) transform without grain growth or necking to free-flowing YAG phase powders. The activation energy for this phase transformation was ≈100 kJ/mol, much lower than values reported for amorphous Y 3 Al 5 O 12 .

A New Y3Al5O12 Phase Produced by Liquid‐Feed Flame Spray Pyrolysis (LF‐FSP)

“…The resulting nanopowder was found to form a new hexagonal Y 3 Al 5 O 12 phase, which we describe here. In studies reported in detail elsewhere, [13] we found that 3:5 mixtures of Y(O 2 CCH 2 CH 3 ) 2 OH and Al(Acac) 3 (Acac = acetylacetonate) dissolved in ethanol gave nanopowders with average particle sizes (APS) below 50 nm (Fig. 1a).…”

“…(LF-FSP). [13] In this process, metallo-organic precursors (e.g., metal carboxylates) with the exact composition of the metals desired in the final oxide nanopowders are dissolved in an alcohol (typically ethanol) and the solutions aerosolized with oxygen. The aerosol mist is ignited to produce flame temperatures exceeding 1500 C. Rapid quenching of the gas-phase species produces nanosized oxide ªsootº with the exact metal composition of the starting solution, including any impurities or dopants.…”

Energy Consumption During Nanoparticle Production: How Economic is Dry Synthesis?

“…Amongst others, nanoparticles of ceria, yttrium stabilized zirconia (YSZ), ceria-zirconia (CeZrO 4 ) or other mixed-oxides (Backman et al, 2004;Marchal et al, 2004;Makela et al, 2004) in general are produced next to optical components or polishing additives (Madler et al, 2002b). Milling has been suggested as a possible route to nanoparticles and has successfully be implemented in YSZ production (Michel et al, 1993).…”

Flame-spray pyrolysis preparation of perovskites for methane catalytic combustion

“…Formerly, the main limitation was due to the availability of volatile precursors to be fed to the flame. More recently, aerosol or liquid-feed flame pyrolysis (FP) allowed to overcome the low productivity problem, hence widely extending the application field of flame synthesis [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Among the methods proposed, the spray FP seems the most interesting for the production of perovskitic oxides, since it does not require volatile precursors.…”