Copper (I) oxide powder generation by spray pyrolysis
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Copper (I) oxide powder generation by spray pyrolysis D. Majumdar, T. A. Shefelbine, and T. T. Kodasa) Center for Micro-engineered Ceramics, Department of Chemical Engineering, University of New Mexico, Albuquerque, New Mexico 87131
H. D. Glicksman DuPont Electronics, DuPont Company, Experimental Station Building E334, P.O. Box 80334, Wilmington, Delaware 19880 (Received 24 August 1995; accepted 20 May 1996)
Copper oxide powders were prepared by the spray pyrolysis of copper nitrate solutions over a range of temperatures (400–1300 ±C) and residence times (3–7 s). Phase-pure [by x-ray diffraction (XRD)] copper (I) oxide was obtained at 800 –1300 ±C in an inert (nitrogen) atmosphere. The particles varied from smooth, solid spheres at 1300 ±C to irregularly shaped and hollow particles at 800 ±C with dense particles of Cu2 O being made only at 1000 ±C or higher. The particles were polycrystalline with an average crystallite size of 42 nm at 800 ±C, while at 1000–1200 ±C, the particles were single crystals. Spray pyrolysis in forming gas (7% H2 –N2 ) atmosphere at 500 –700 ±C gave Cu while spray pyrolysis in air yielded CuO over 800–1000 ±C and a mixture of Cu2 OyCuO at 1200 ±C. These results show that solid, phase-pure Cu2 O particles can be produced by aerosol-phase densification at temperatures below its melting point (1235 ±C).
I. INTRODUCTION
Copper oxides are finding applications in a growing number of fields. Copper (I) oxide is a p-type semiconductor and exhibits luminescence.1 Thin-film oxygen pressure sensors have been made from copper (I) oxide.2 In powder form, copper (I) oxide has applications as a binder in pastes for thick-film microelectronic circuits.3 The addition of copper (I) oxide to thick-film copper pastes can greatly reduce the maximum firing temperature.4 This addition also ensures good adhesion and conductivity of the baked paste and good brazing and contacting capacity without the risk of migration of copper to the brazing alloy and vice versa. This type of paste can also be used in cases where specific electrical (high-frequency or low-noise) or physical and chemical (compatibility of the copper paste with dielectric and resistor pastes) properties are required. The binder particles should be spherical and unagglomerated to facilitate paste formation and exhibit good sintering behavior during firing of thick-film patterns.5 With increasing circuit complexity and decreasing feature sizes, thickfilm pastes must meet the above requirements and also be composed of dense, submicron-sized, pure, chemically uniform particles with controlled phase composition for optimal properties. Numerous solution techniques are available for the preparation of metal and ceramic powders for pastes. a)
Author to whom correspondence should be addressed. J. Mater. Res., Vol. 11, No. 11, Nov 1996
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Most ceramic powders made by precipitation from solutions have to be calcined and milled after drying, thereby negatin
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