Preparation of Copper Aluminium Oxide by Spray Pyrolysis
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Preparation of Copper Aluminium Oxide by Spray Pyrolysis Ji Youn Rim, Shin Ae Song and Seung Bin Park Korea Advanced Institute of Science and Technology, Dept. of Chemical Engineering, 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701, Republic of Korea ABSTRACT Copper aluminium oxide(CuAlO2) particles, a promissing p-type TCO(transparent conducting oxide), were prepared by spray pyrolysis. Delafossite phase of CuAlO2 was obtained when copper nitrate, copper acetate and copper sulfate, divalent copper precursors, were used as copper precursor and aluminium nitrate as aluminium precursors. However, when copper chloride (CuCl, a monovalent copper precursor) was used, the delafossite phase was not obtained regardless of the type of aluminium precursor. The O2-doped CuAlO2 was obtained by using oxygen as carrier gas.
INTRODUCTION The CuAlO2 particles are prepared by solid-state reactions of Cu2O and Al2O3.[1] Solid-state reaction method is cheap and oxide precursors are readily available. But this method needs repeated milling and calcination, and the prepared particles have irregular morphology and large size. The spray pyrolysis has some advantages in comparison to the solid-state reaction method. Spray pyrolysis is simple and has the ability to produce chemically homogeneous multi-metal oxides[2]. A wide variety of reactants can be used as long as they have proper solvent. This flexibility allows the use of inexpensive reactants such as metal nitrates, chlorides, fluorides, etc. In this work, copper aluminium oxide particles with delafossite were prepared by the spray pyrolysis for the first time. Various metal salts were used as precursors, and their effects on the crystal structure were investigated. The bulk conductivity of CuAlO2 is known to be 1.7×10-3 S/cm [3] and the origin of positive hole in CuAlO2 is not clear but may be excess oxygen[4]. To obtain higher conductivity, M. S. Lee et al. annealed CuAlO2 pellet at 943 K under O2 atmosphere for O2 doping to CuAlO2. However, the doping process decomposed CuAlO2 into CuO and CuAl2O4[5]. Therefore, the particles were prepared by using oxygen as carrier gas to prepare O2 doped CuAlO2
EXPERIMENTAL DETAILS The spray pyrolysis system consisted of an ultrasonic nebulizer and a reaction furnace. The stock solution was atomized with a sonicator equipped with 1.7 MHz resonator. Copper nitrate, copper acetate, copper sulfate ( divalent copper precursors) and copper chloride (a monovlent copper precursor) were tested as copper precursors and aluminium nitrate, aluminium chloride and aluminium sulfate were tested as aluminium precursors. Stock solutions of 0.5 M were prepared by dissolving copper and aluminium precursors into two different solvents. Copper chloride was dissolved into 15 wt.% HCl because of its low solubility in pure water and the other precursors were dissolved in distilled water. The reactor temperature was fixed at 973 K. The flow rate of carrier gas was 4 L/min. Air, N2 and O2 were used as carrier gas. The as-prepared V6.9.1
particles were annealed at
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