Abstract:We show that fully dense nanocrystalline titanate ceramic could be obtained by full crystallization from glass which was prepared by a novel contactless solidification process. Through annealing above glass transition temperature T g for prescribed duration, BaTi 2 O 5 ceramic with grain size of 20-130 nm was successfully fabricated. The dependence of the nanoceramic's dielectric constant and dissipation on frequency was investigated. The results show clearly that the dielectric constant of BaTi 2 O 5 nanoceramic depends on average grain size in nanometer scale, and an optimal range of the grain size is found which exhibits greater dielectric constant than conventional microcrystalline ceramics. The as-fabricated ceramic also possesses lower dielectric dissipation, which can be mainly attributed to the presence of nanometer-sized grains.

Nanometre-sized spherical glasses without conventional networkforming oxides were fabricated for the first time using a novel contactless phase change process. The as-fabricated titanate nanomaterials possess perfect spherical shape and superior optical properties such as high refractive index and wide-banded transmittance from 250 nm to 11 mm. We believe that these unique nanospheres may find significant applications such as antireflective coatings for photovoltaic devices, and the synthesis approach can be extended to a wide range of metastable nanomaterials.Conventional glasses contain sufficient network-forming oxides such as silicates and borates, which result in a disordered three-dimensional network over a long range consisting of interconnected polyhedral structural elements. In recent years, glasses lacking networkformer (LNF) have attracted extensive attention owing to their significance in fundamental research (Mg 2 SiO 4 ) 1 and large potential in applied optics (Al 2 O 3 -Y 2 O 3 , La 2 O 3 -Nb 2 O 5 , etc.), 2-5 microelectronics (BaO-TiO 2 ), 6 and mechanics (Al 2 O 3 -Re 2 O 3 ). 7 Because of their deficient glass-forming ability, LNF glasses cannot be obtained through conventional industrial techniques (e.g. float process). The alternative approaches must be able to kinetically freeze the melt to an amorphous solid state. Yu and coworkers 3,5,9 fabricated a BaTi 2 O 5 (BTO) glass in $2 mm ellipsoidal bulk form without adding any network-forming oxides. Their method involved a containerless solidification process using an aerodynamic levitator (ADL), which enables deep undercooling of molten materials because it suppresses inhomogeneous nucleation from the container wall. The structural analysis revealed that the BTO glass obtained in this way has unusual features, consisting of distorted Ti-O polyhedra with an average coordination number of approximately 5. [8][9][10][11] As a result, BTO glass