The Seeding Effect of Lanthanum Nickel Oxide Ceramic/Ceramic Nanocomposite Thin Films Prepared by the MOD Method
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Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong China ABSTRCT Lanthanum nickel oxide (LNO) is a conducting ceramic which has potential to be used as electrodes in multilayer ceramic actuators. Thick LNO films have been formed by incorporating nanosized LNO powder (annealed at 700"C, with diameter around 100 nm) into a LNO solution prepared by a metal-organic decomposed ( MOD ) method. Three different weight percents, 2%, 4%, and 10% of LNO powder have been added. The structural variation of the ceramic/ceramic composite film with annealing temperature was studied by X-ray diffraction and differential thermal analysis. The crystallization temperature of the film is found to decrease from -590'C to -5 10°C due to the seeding effect introduced by the nano-powder. Key words: seeding effect, metallic organic decomposition ( MOD ), Lanthanum Nickel Oxide INTRODUCTION Nanosized particles are of interest in fundamental as well as applied research because many material- properties change drastically when the crystallite size reaches the nano/submicrometer range [1]. Since nano-scaled particles have relatively larger surface areas, they tend to agglomerate to minimize the total surface energy. Agglomeration adversely affects their properties [2,3], for example: different reaction temperature, faster grain growth speed, closer and more uniform film quality, etc. Recently, it has been reported that the formation of PZT thin film may be controlled by seeding with PZT powder [I]. Applying the seeding effect in order to enhance the transformation kinetics and to control the development of a desired phase has been successfully investigated. Lanthanum nickel oxide (LNO) is a conductive ceramic material that can be used in fabricating interleaving electrodes in PZT multilayer devices[2,3,4]. In this work, new investigation of using seeding effect to reduce the annealing temperature of LNO films is presented. Various weight percentage of nano-sized lanthanum nickel oxide (LNO) powder fabricated by MOD method were added into a 0.5M LNO solution [4,6] as seeds. Then the LNO film was spin-coated onto a Pt/Ti/SiO 2 /Si multilayer substrate. Using rapid thermal annealing process (RTA) and by changing the annealing temperature and annealing time, samples with different properties were obtained. EXPERIMENTS Lanthanum nickel oxide (LNO) powder has been produced by using a metal-organic decomposed (MOD) method [4,5] and annealed at 700'C for 60 minutes. The crystallization process of LNO was studied by X-ray diffraction (XRD, Philips x'pert XRD system), and differential thermal analysis (DTA, Perkin-Elmer 1700). The LNO metal-organic decomposed solution was produced by combining the La(N0 3 )3 and Ni(NO 3 )3 solutions in a molar ratio of 1: 1. The concentration of the final solution was about 0.5 M. Polyvinyl alcohol (PVA) with a weight percentage of about 5% was added as a binder. A 389 Mat. Res. Soc. Symp. Proc. Vol. 623 © 2000 Materials Research Society
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