Comparison of Solid‐State and Spray‐Pyrolysis Synthesis of Yttrium Aluminate Powders

Abstract

rather conditions on the formation of yttrium aluminum garnet, Y 3 Al 5 O 12 (YAG), was investigated using "single-source" pre-than YAG when reacting a mixture of precursors with 3:5 cursors (cohydrolyzed yttrium and aluminum alkoxides Y:Al molar ratio. 11-14 Second, the stiffness of YAG (Young's and yttrium aluminum glycolates) and "multiple-source"modulus, E, of 333 GPa) creates a dichotomy in refractory precursors (mixtures of metal nitrates and mixtures of sepaceramic applications, because a high temperature is necessary rately hydrolyzed yttrium and aluminum alkoxides). Phasefor sintering, which can result in increased grain size and consepure YAG was formed only in the solid-state thermal quential loss of structural integrity. The latter problem may be decomposition experiments. The lack of formation of YAG addressed by using powder synthesis techniques, such as spray in all the spray-pyrolysis experiments was ascribed to the pyrolysis, that produce highly dispersed powders that can, in short heating times and fast heating rates, which resulted in many cases, be sintered at lower temperatures. However, the the formation of kinetic products. In the case of the metal high heating rates and short heating times inherent to the spraynitrates, an additional factor that influenced product forpyrolysis process 15 may lead to the formation of kinetically mation was the difference in thermal reactivity of the prestable phases such as YAlO 3 and YAM, rather than the target cursors. It was concluded that the formation of complex thermodynamically stable phase. In fact, despite some attempts, metal oxide materials by conventional or aerosol routes is YAG has never been produced by spray-pyrolysis techniques. 14 not necessarily achieved by the use of a chemically homoge-We have investigated the potential of forming phase-pure neous precursor, such as a single-source precursor. It also YAG powders via the following set of experiments: was necessary to ensure that the precursors and intermedi-(1) Yttrium aluminate powders are synthesized by the ates have similar thermal decomposition temperatures to solid-state thermal decomposition of several 3:5 Y:Al precursor avoid phase segregation in the initial stages of thermal systems, to determine the influence of precursor homogeneity decomposition.on the phase content of metal oxide powders that are obtained by the thermal decomposition of "single-source" and "multiplesource" precursors. A single-source precursor for a heterometal I. Introduction oxide, A x B y O z , is a single molecule that contains metals A and D. W. Johnson Jr.-contributing editor zation suppressant. The error in all AA measurements was approximately Ϯ5 at.%. Electron microprobe analysis (EMPA) of the powder samples was conducted using an electron micro-Manuscript No. 192526.

Design of particles by spray pyrolysis and recent progress in its application

“…A dimensionless number, Weber number, is a measure of the magnitude of relative strength of these two forces. Metal-organic compounds Improve volatility for application in AACVD and in gas-to-particle conversion Acetate [4], Oxalate [5], Butoxide [6], Alkoxide [7], Cu(hfac) 2 [8] Organometallic compounds Improve volatility for application in AACVD and in gas-to-particle conversion Sn(CH 3 ) 4 [9], Al(i-Bu) 3 [10] Colloid Control porosity of particles Particulate sol [11], Polymeric sol [12], November, 2010…”

Synthesis of Cerium‐Activated Yttrium Aluminate Based Fine Phosphors by an Aerosol Route

“…The yttria-alumina phase diagram, [12,13] in which the ratio of 2:1 refers to the formation of monoclinic Y 4 Al 2 O 9 and 3:5 refers to the formation of garnet Y 3 Al 5 O 12 , evidences that the structures of the compositions are not straightforward and that the equilibrium reaction [Equation (1)] leads rather to dissociation than to the formation of the multiphase system.…”

“…[21,22] There are certain process parameters, such as high heating and cooling rates, short residence times, and an additional thermal treatment, which may affect the yield of either thermodynamically (YAG, YAM) or kinetically (YAP) stable phases. [12] The introduction of organic components into the solution is becoming increasingly popular, since these components provide the retention of the proper stoichiometry during the process, and the reaction that occurs in the solution leads to volume precipitation and the formation of dense particles. A pure YAP phase can already be synthesised through a classical sol-gel route, but the obtained particles are of irregular shape and size, which is due to extensive agglomeration.…”

Synthesis of cubic yttrium aluminum garnet (YAG) powders by co-precipitation and two-step calcinations

“…Various wet-chemical methods have been developed and successfully used to synthesize pure and / or doped YAG. These involve precipitation [1,4,7,9,[14][15][16][17][18][19][20][21][22][23][24][25] , sol-gel [1,17,[26][27][28] , citrate gel [29] , hydrothermal [30] , solvothermal [6,31] , supercritical water [32,33] , combustion [34,35] , spray-pyrolysis [36,37] , microemulsion [38] , microwave irradiation [39] and modified Pechini routes [40] . Among them, precipitation method is one of the most commonly used techniques, because homogeneous multi-element compounds from which can be prepared effectively on a large scale and final products with improving phase purity can be formed at the temperature below 1000 °C.…”