March 1998 Ž . Materials Letters 34 1998 188–195 A novel reductive nitrogenation approach for synthesizing aluminum nitride powders Jin Yong Kim, Prashant N. Kumta ) Department of Materials Science and Engineering, Carnegie Mellon UniÕersity, Pittsburgh, PA 15213, USA Received 15 May 1997; revised 1 June 1997; accepted 6 June 1997 Abstract A novel low temperature chemical approach has been developed for synthesizing aluminum nitride powders. The process Ž . Ž . involves the reaction of aluminum trichloride AlCl with anhydrous hydrazine NH in an acetonitrile solution in the 3 2 4 presence of metallic lithium to induce a reductive precipitation reaction. Results of the XRD analyses conducted on the pyrolyzed powders obtained after heat-treatment at 8008C in either UHP-Ar or NH indicate the formation of a mixture of 3 Ž . hexagonal AlN and lithium chloride LiCl . LiCl can be removed either by washing with acetone or by subsequent heat-treatment of the precursors in UHP-Ar or NH beyond 10008C, resulting in single-phase hexagonal AlN powders. This 3 new approach therefore demonstrates the potential for synthesizing precursors at room temperature for the subsequent generation of AlN powders at temperatures as low as 8008C. q 1998 Elsevier Science B.V. PACS: 81.05.Ea; 81.06.Je; 81.05.Rn; 81.10.Dn; 81.20.Ka Ž . Ž . Keywords: Aluminum nitride AlN ; Synthesis; Aluminum trichloride; Hydrazine; Reductive nitrogenation; X-ray diffraction XRD ; Ž . Scanning electron microscopy SEM 1. Introduction Aluminum nitride has received considerable atten- tion as a substrate material in electronic packaging due to its high thermal conductivity, high electrical resistivity, low density and good thermal expansion w x match with silicon 1–6 . It is well known that impurities, especially oxygen, has a deleterious ef- wx fect on the thermal conductivity of AlN 1 . There- fore, the synthesis of high-purity AlN is very critical ) Corresponding author. Tel.: q1-412-2688739; fax: q1-412- 2687596; e-mail: kumta@cmu.edu. for processing high-thermal-conductivity substrates for packaging. Carbothermal reduction of alumina and direct nitridation of aluminum metal are typi- cally the two common approaches used to synthesize w x AlN powders 7–9 . Even though these processes are carried out at high temperatures, they still require prolonged exposure for completion of the reaction. Furthermore, carbothermal reduction requires a sub- sequent oxidation step in controlled atmospheres to ensure the removal of residual carbon, that can con- tribute to oxygen contamination of the AlN powders. In recent years, there have been a number of chemical based alternate approaches developed to synthesize AlN utilizing organometallic precursors 00167-577Xr98r$19.00 q 1998 Elsevier Science B.V. All rights reserved. Ž . PII S0167-577X 97 00169-9