Amorphous titanate nanospheres fabricated using a contactless phase change process

Abstract

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

Upconversion 32Nb2O5–10La2O3–16ZrO2 glass activated with Er3+/Yb3+ and dye sensitized solar cell application

“…After the laser power was turned off, the homogeneous melts of NLZ1-4 and NLZ6-9 were quenched into transparent solid spherical glasses with a diameter size of ~3 mm at an approximate cooling rate of 250 ℃/s. The details about ADL furnace have been introduced elsewhere [24,25]. A video camera with high-resolution charge-coupled device was applied to realize the magnified in situ observation of the samples.…”

An amorphous barium titanate thin film improves light trapping in Si solar cells

“…Shift current is yet another dominant mechanism in bulk BTO as photocurrent does not only depend on the magnitude of material polarization, but also on electronic states with delocalized, covalent 4 bonding that is highly asymmetric along the current direction [13]. However, nanometer-sized BTO glass has wider transmittance window 250 nm -11,000 nm and high refractive index ~ 2.15 which offers lower reflectance to the Si based photovoltaic devices [14]. Amorphous BTO thin films of 140 nm thick deposited using metalorganic chemical vapor deposition was reported to show high optical transmittance of 80 % with optical band gap of 4.71 eV in the visible wavelength range [15].…”

An Upconversion Niobium Pentoxide Bulk Glass Codoped with Er3+/Yb3+ Fabricated by Aerodynamic Levitation Method

“…Under these circumstances, the melt can transform into glass. In our previous works, TiO 2 ‐ and Nb 2 O 5 ‐based glasses with high index of refraction have been successfully fabricated by a containerless method, and exhibit excellent optical properties from the network former‐free glasses. According to the reference, it is found that TiO 2 ‐based bulk glasses doped with different rare‐earth elements can emit intense upconversion luminescence …”