Non-Hydrolytic Solution-Phase Synthesis of Anisotropic LiNbO 3 and Nb 2 O 5 Nanostructures
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1087-V08-21
Non-Hydrolytic Solution-Phase Synthesis of Anisotropic LiNbO3 and Nb2O5 Nanostructures Bryan D. Wood, and Byron D. Gates Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A1S6, Canada ABSTRACT This paper describes an innovative and simple technique to synthesize anisotropic nanostructures of both lithium niobate (LiNbO3) and niobium oxide (Nb2O5). These materials were obtained using a solution-phase non-hydrolytic decomposition of LiNb(OPri)6 with or without the presence of Nb and Li-chlorides. The stability of LiCl is suggested as an explanation for the lack of LiNbO3 production in the chloride-based reaction. After 2 and 24 hours of reaction crystalline products of Nb2O5 and LiNbO3 are obtained without further thermal treatment. The products of both reactions contained a mixture of spherical and rod-like morphologies. Larger crystals of LiNbO3 and Nb2O5 were predominantly found to be anisotropic with aspect ratios of 7:1 and 3:1, respectively. These structures are believed to result from the natural anisotropy of the unit cell for these materials and from the use of triphenylphosphine oxide (TPPO) as a coordinating solvent. Our solution-phase synthesis is easily scaled-up as a one-pot procedure that offers a promising route to controlling crystal size and morphology. Details of the composition and the growth of our LiNbO3 and Nb2O5 nanostructures will be discussed in addition to the details of our experimental procedure. INTRODUCTION The structural anisotropy of crystalline perovskites and distorted perovskites creates intrinsic properties that are desirable for mechanical, electrical, and optical devices. Lithium niobate, LiNbO3, is one such material that has found widespread application due to a large pyroelectric, piezoelectric, electro-optic and photoelastic susceptibility [1] inherent to specific crystal orientations. These devices rely on an efficient synthetic approach to crystalline materials with well-defined principle axes and composition. For the majority of its present use, commercial crystals of LiNbO3 are typically grown as a boule from melt solutions. These boules are then cut to size and polished to expose the desired crystalline face. Commercial thin-films, used in other applications, are largely produced by vapour deposition methods. These methods are restricted to a growth direction determined by the chosen substrate. Once this film has been deposited, etching is necessary to produce the required feature shape and size. Both the thin-film and boule processes can be foreseen to become more tedious with the continued miniaturization of device components. Herein, we address the need to develop a single synthetic approach to control the size, shape and composition of crystalline LiNbO3. One synthetic strategy to regulate crystal size and shape is by means of a coordinating solution. This technique has been applied in our research because it has been shown to permit an extraordinary level of control over the size and morphology of the
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