Morphology Control Of Phosphor Particles

This dissertation is focused on the studies of the particle morphology control and the luminescent properties of the luminescent materials. The main results are summarized as follows:1.Y₃Al₅O₁₂:Tb³⁺ and Y₂SiO₅:Ce³⁺ phosphors with fine morphology and good photoluminescence were prepared by using a sol-gel method. Cathodo-luminescence intensity of Y₃Al₅O₁₂:Tb³⁺ is 140% of commercial phosphors at low voltage.2. The process of particle growth of Y₃Al₅O₁₂:Tb³⁺ and Y₂SiO₅:Ce³⁺ phosphors were investigated, and the reasonable mechanisms of particle growth were given: With enhancing the heating temperature, the large particles broke into small ones continually while the grain size slightly increased. The final product has the particle size about 1μm, which is agglomerated by several small grains with tens nanometer size.3. A potential luminescent material was provided: amorphous Y₃Al₅O^<sub>12:Tb³⁺ phosphors, with good photoluminescence were prepared by using a sol-gel method. Photoluminescence intensity of amorphous Y₃Al₅O₁₂:Tb³⁺ sample is about 70% of polycrystalline phosphors at low temperature such as 600℃.4. A unusual bright blue emission in amorphous Y₃Al₅O₁₂:Tb³⁺ system was observed, and a reasonable luminescent mechanism is given as follows: the blue emission may arise from some dangling bonds or unsaturated bonds on the surface of samples. Besides, a series of unique excitation spectra of amorphous Y Y₃Al₅O₁₂:Tb³⁺ were investigated, the dominating peak shifts with variational heating temperature.5. A novel method for improving particle distribution and luminescent properties of Y₂SiO₅:Ce³⁺ phosphors by coating method were provided. And a mechanism for the particle size reduction was proposed: After coating layers are precipitated on the surface of the grains, some stuff is filled in the neck area formed due to grain contact. When the sample is annealed, the thickness of the coated layers shrink and the internal stress formed in the coating layer around the neck area. If the stress is unbalanced and stronger than the contact bonding between the grains, the bonding is broken and the particles become smaller.