Elucidating the role of precursors in synthesizing single crystalline lithium niobate nanomaterials: a study of effects of lithium precursors on nanoparticle quality

Abstract

A number of solution-based procedures have been realized for the synthesis of lithium niobate (LiNbO₃) nanoparticles (NPs). Relatively little is, however, known about the influences of the selection of lithium (Li) precursors on the resulting dimensions, shapes, crystallinity, and purity of the products. A comparative study is provided herein on the role of different Li precursors during the synthesis of LiNbO₃ NPs. To the best of our knowledge, this study provides the first systematic comparison of the effects of various Li reagents on the preparation of LiNbO₃ NPs through solvothermal processes. This solution-phase approach was tuned by the inclusion of Li precursors that either lacked carbon based anions (e.g., F⁻, Cl⁻, Br⁻, I⁻, OH⁻, NO₃⁻, or SO₄²⁻) or contained carbon-based anions (e.g., C₂H₅O⁻, C₂H₃OO⁻, C₅H₇OO⁻, or CO₃²⁻). All other variables were held constant during the synthesis, such as reaction temperature, solvent, niobium precursor, and surfactants. The results of these studies suggest that the type of Li precursor selected plays an important role in nanoparticle formation, such as through controlling the uniformity, crystallinity, and aggregation of LiNbO₃ NPs. The average diameter of the resulting NPs can also vary from ∼30 to ∼830 nm as a function of the Li reagent used in the synthesis. The selection of Li precursors also influences the phase purity of the products. This comparative study on the preparation of crystalline LiNbO₃ NPs represents a critical step forward to understand the influences and roles of precursors in the design of synthetic processes for the preparation of a variety of alkali metal niobates (e.g., including NaNbO₃ and KNbO₃) and crystalline metal oxide-based NPs containing other transition metals (e.g., titanium, tantalum).