New luminescent materials and high-performance solution-processed oxide thin films

Graduation date: 2011Crystals of an incongruent-melting compound, Ba₃MgSi₂O₈, were grown by the flux method and its structure was determined by single crystal X-ray diffraction methods. Ba₃MgSi₂O₈ crystallizes in trigonal space group P-3[bar]m1 with a = 5.6123(3) Å, c = 7.2667(9) Å and Z = 1. Eu²⁺ ions prefer one crystallographic Ba site in the structure and exhibit strong blue emissions at 440 nm. A new series of compounds RE₄Zn₄(SiO₄)₅ (RE=Y, La, Eu, Gd, Tb, Dy, Ho, Er), adopting an unprecedented new structure type, was discovered. Crystals of Y₄Zn₄(SiO₄)₅ were grown from a silica-rich eutectic melt and its structure was determined by single-crystal diffraction methods. It crystallizes in tetragonal space group P4₂/n with cell dimensions a = 9.3289(10) Å, c = 9.0509(18) Å and Z = 2. Selected photo-luminescence properties of lanthanide ions doped Y₄Zn₄(SiO₄)₅ are presented. High-purity MgS:Eu phosphors, exhibiting distinct cubic morphology, high luminescence efficacy, and stability against moisture, were synthesized. Thin films of early transition metal oxides (TiO₂, HfO₂, Nb₂O₅, and V₂O₅) have been deposited from peroxo-assisted aqueous solutions. The facile decomposition of peroxo ligands upon annealing allows smooth and efficient transformation of the precursors into high-quality films. Therefore, the films exhibit extraordinary performance in advanced optical and electrical devices, such as dielectric mirrors, microcavities, capacitors, and thin-film transistors (TFTs). The control over film thickness to a single-digit nm thickness is also demonstrated through the fabrication of TiO₂−AlPO nanolaminates using simple beaker chemistry