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Abstract: The glass composition 92.5 Li2B4O7–7.5Nb2O5 (mol%) was prepared by the conventional melt quenching technique. The as-quenched sample, blue and transparent, was heat-treated at 550 and 650°C (HT). The glassy nature of the as-quenched sample was established by Differential scanning calorimetry (DSC). Lithium niobate LiNbO3 and Li2B4O7 nanocrystals were produced within the glass by heat-treating it at 550 and 650°C/3. The amorphous nature of the as-quenched glasses and crystallinity of glass nanocrystal composites were confirmed by X-ray powder diffraction studies. Various optical parameters such as optical band gap (E opt) and Urbach energy (ΔE) of these transparent glass–ceramics have been found to be crystallite size dependent. The volume ratio of the particles increases with increase in heat-treatment temperature. The behavior of the σ ac, with the increase in the heat-treatment (HT) temperature, was related with the decrease in the free ions number in the glass matrix and consequent increase in the fraction of the crystallites LiNbO3 phase to the crystallites Li2B4O7 phase and the glass matrix. The dielectric constants of the glass–ceramics decrease with increase in the HT temperature and with increase in frequency (0.12–100kHz). [Copyright &y& Elsevier]

Phase-pure, highly crystalline sub-50 nm LiNbO3 nanocrystals were prepared from a non-aqueous solvothermal process for 72 h at 230 °C and a commercial precursor solution of mixed lithium niobium ethoxide in its parent alcohol. A systematic variation of the reaction medium composition with the addition of different amounts of co-solvent including butanol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol resulted in the formation of nanocrystals of adjustable mean size and shape anisotropy, as demonstrated from XRD measurements and TEM imaging. Colloidal stability of ethanol- and water-based suspensions was evaluated from dynamic light scattering (DLS)/zeta potential studies and correlated with FTIR data. Thanks to the evolution in the nanocrystal size and shape distribution we observed, as well as to the available literature on the alkoxide chemistry, the reaction pathways and growth mechanisms were finally discussed with a special attention on the monomer formation rate, leading to the nucleation step. The polar, non-perovskite crystalline structure of LiNbO3 was also evidenced to play a major role in the nanocrystal shape anisotropy. [ABSTRACT FROM AUTHOR]