Journal of Electroceramics 2:3, 157±162, 1998 # 1998 Kluwer Academic Publishers, Boston. Manufactured in The Netherlands. Sol-gel Synthesis of Lithium Niobate Powder and Thin Films Using Lithium 2,4-Pentanedionate as Lithium Source ALAMANDAV. PRASADA RAO, DONG SOO PAIK & SRIDHAR KOMARNENI Intercollege Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802 Submitted August 22, 1997; Revised April 9, 1998; Accepted April 15, 1998 Abstract. Lithium niobate powder was prepared at 500  C by a sol-gel method using lithium 2,4-pentanedionate as the lithium source. This method offers an advantage over the double alkoxide method as lithium 2,4- pentanedionate is less prone to moisture as compared to lithium ethoxide precursor and also it is easily soluble in 2- methoxyethanol. Microstructural investigation revealed sub- micrometer gel powder heat treated at 600  C. Thin ®lms of lithium niobate with no preferred orientation were obtained at 350  C by spin coating of the above precursor solution onto platinum coated silicon substrates. Keywords: sol-gel synthesis, crystallization, microstructure 1. Introduction Lithium niobate, LiNbO 3 , exhibits a large non-linear optical coef®cient, a large birefringence, a high electro-optic coef®cient, a high Curie temperature, good piezoelectric and excellent acousto-optic prop- erties which makes it suitable for many applications such as optical wave guides, optical modulators, optical switches and SAW (surface acoustic wave) devices [1]. Single crystals of LiNbO 3 are grown by Czochralski method from melts with non-stoichio- metric congruent composition of 48.5 mol% Li 2 O [2]. Polycrystalline powders are generally prepared via solid-state reaction between lithium carbonate and niobium pentoxide [3] which require high tempera- tures that might lead to compositional defects due to volatilization of Li 2 O [4]. Also since several proper- ties such as refractive index and Curie temperature of LiNbO 3 are very sensitive to even slight composi- tional ¯uctuations [5], low temperature chemical processing with a good control over stoichiometry is highly desirable for reproducible properties. Two such chemical processes have been reported in literature for the synthesis of LiNbO 3 powders. Lanfredi et al. [6] described an evaporative method based on thermal decomposition of a precursor salt obtained by coprecipitation, while Hirano and Kato [7], Castings et al. [8] derived LiNbO 3 from metalorganic precursors. In the recent years, in order to produce integrated electro-optic devices, signi®cant efforts have been focused on the fabrication of LiNbO 3 thin ®lms using liquid phase epitaxy, chemical vapor deposition, and rf-sputtering and sol-gel methods. Since sol-gel technique offers low processing temperature and precise control over stoichiometry, epitaxial growth of LiNbO 3 ®lms on sapphire, LiNbO 3 , MgO doped LiNbO 3 and LiTaO 3 substrates in particular have been thoroughly investigated [9± 18]. All the above sol-gel based methods made use of lithium alkoxide as lithium source. Besides lithium alkoxide or lithium acetate was also used as lithium source [19]. Since lithium ethoxide is extremely hygroscopic and since lithium acetate has limited solubility in 2-methoxyethanol (solvent used in sol- gel process), use of lithium 2,4-pentanedionate has been explored. This paper describes the use of lithium 2,4-pentanedionate as lithium precursor for the fabrication of LiNbO 3 powders and thin ®lms.