Room-temperature synthesis of submicron platinum and palladium powders in glycols
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Room-temperature synthesis of submicron platinum and palladium powders in glycols K. Tekaia-Elhsissen, F. Bonet, S. Grugeon, S. Lambert, and R. Herrera-Urbinaa) Universite´ de Picardie Jules Verne, Laboratoire de Re´activite´ et de Chimie des Solides, UPRES-A 6007, 80039 Amiens, France (Received 1 February 1999; accepted 28 May 1999)
Platinum and palladium powders with average particle sizes in the submicron range have been synthesized at room temperature by hydrazine reduction of PtCl62− and Pd(NH3)2+ 4 , respectively, in glycols. Platinum powders contain spherical particles with a bimodal size distribution. Palladium powders also contain spherical particles, but the size distribution is narrow. The effect of both ammonia and hydrazine concentration on the size distribution and average size of palladium particles was investigated.
I. INTRODUCTION
Platinum and palladium powders with a narrow particle size distribution, uniform particle shape, low degree of agglomeration, and submicron average size are widely used as conductor materials in the electronics industry.1–3 Palladium powders are also used for the production of internal electrodes of multilayer ceramic capacitors (MLCC). Smoother electrodes, formed from powders with better packing characteristics, are needed for increasing the performance of the thinner dielectric layers.3 Better packing of powders is achieved with spherical, monodisperse particles with an average particle size below 0.5 m. Consumption of palladium by the electronics industry accounts for around 47% of the total demand.4 Several methods, both at low and high temperature, are known to yield metallic platinum and palladium in particulate form. The requirements of the electronics industry for these noble metal powders, however, are seldom fulfilled by classical methods of powder metallurgy such as atomizing or grinding. Under strictly controlled conditions, solution chemistry methods allow production of high-quality platinum and palladium powders with tailor-made characteristics for the electronics industry. Platinum powders synthesized from aqueous solutions, for example, are generally extremely fine (average particle size between 0.2 and 0.5 m) and catalytically active.1 As opposed to the synthesis of colloidal platinum and palladium, the synthesis of submicron particles of these
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Present address: Departamento de Ingenierı´a Quı´mica y Metalurgia, Universidad de Sonora, 83000 Hermosillo, Sonora, Mexico. J. Mater. Res., Vol. 14, No. 9, Sep 1999
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metals from solution is not easily accomplished. For example, chemical reduction of aqueous chloroplatinic acid in the presence of a protective agent yields fine platinum particles (≅10 to 100 Å).5 Nakao and Kaeriyama6 have obtained palladium colloids by sodium borohydride reduction of palladium chloride in an aqueous solution containing a protective agent. More recently, Ayyappan et al.7 and Teranishi and Miyake8 prepared palladium nanoparti
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