SBIR-STTR Award

This STTR Phase I project is aimed at producing high-value phosphor powders for field emissive displays (FEDs) by spray pyrolysis. The next generation flat panel displays (FPDs) are called FEDs and create displays images of comparable quality to the cathode ray tubes (CRTs) found in television sets or desktop computer monitors. FEDs allow for ultra-thin, lightweight, lower power packages by eliminating the size, weight, and power consumption problems of CRTs. In order to successfully develop FEDs, it is necessary to make significant improvements in the properties of phosphor powders. Exist in solid-state synthetic routes to phosphor powders are limited in their ability to control these properties. Spray pyrolysis is a materials synthesis technique which under carefully controlled conditions can be used to form high-purity , controlled stoichiometry, chemically homogeneous powders with controlled particle size, particle size distribution and crystallinity that can be scaled to commercial manufacturing quantities. We believe thatthis technique will result in formation of phosphor powders with much ad of size distribution), better improved efficiency (through better control over particle size and spre controlled emission spectrum (through better control over chemical homogeneity and stoichiometry) and improved persistence (through control of crystallinity) as a result of the better control over powder properties that spray pyrolysis permits. The Phase I effort will prove the feasibility of spray pyrolysis as a method to produce phosphor powders by preparing three types of phosphors: Type 1, copper and silver doped metal sulfides; Type 2, rare earth doped yttria and Type 3, rare earth doped perovskites such as CaTiO3.

Keywords:
Spray Pyrolysis Phosphor Powders Displays

It is generally agreed that for a significant advance to be made in the development of devices that rely on luminescent properties the development of higher efficient phosphor powders with controlled emission characteristics is the key factor. The ONR funded Phase I Research awarded to Nanochem Research, Inc. addressed this problem by demonstrating the feasibility of producing high quality phosphor powders by spray pyrolysis. Nanochem Research, Inc. demonstrated the ability to produce a variety of phosphor powders including binary and ternary oxides, group 2 (e.g. CaS, SrS) and (e.g. ZnS, CdS) sulfides and (e.g. yttrium) fluorides. The powders produced have luminescence intensities comparable to commercial powders and have several distinct advantages including spherical morphology, controllable crystallinity and particle size, control of spread of particle size distribution, homogeneous particle formation and production of non-agglomerated particles without milling. These powders have attracted commercial interest for use in field emissive displays, optical storage devices and powder electroluminescent backlights. In order to better demonstrate the market potential of these materials the Phase II proposal is focused on scale-up of the powder synthesis process to produce phosphor powder on a commercial scale. A plan for designing, building, testing and refining a pre-production prototype spray pyrolysis reactor capable of producing coated phosphor powders is described. The powders will be characterized by standard materials characterization techniques through a collaboration with the Center for Micro-Engineered Materials at the University of New Mexico. The luminescent properties of the powders will be tested through the ability to make sufficient quantities to incorporate into luminescent devices through partnerships with potential customers.

Keywords:
Phosphors Spray Pyrolysis Powders Aerosol Decomposition Luminescent Display Storage