Phosphor Development

The Materials & Processes group at SRI has extensive experience in the use of fluidized-bed reactor chemical vapor deposition (FBRCVD) and other deposition techniques, to coat phosphor powders for enhanced performance. In particular, we have shown that the operating lifetime of normal cathodoluminescent phosphors, such as ZnO, ZnS, YVO3, and ZnSiO3-based phosphors, can be significantly increased (under electron bombardment from Spindt cathodes) when coated with a thin layer of a dielectric, such as silica, using FBRCVD.

This technique has also been used to coat upconverting phosphors (oxides and fluorides) in order to tailor the surface chemistry for processing needs; for example, with respect to rheology, inertness to liquids, and specific chemical interactions (in particular, antigen attachment). Furthermore, a variety of phosphor substrates have been coated using FBRCVD in attempts to enhance luminosity.

We have an extensive range of fluidized-bed reactors and can custom-manufacture if necessary from laboratory-scale reactors, coating a few grams of material, to pilot-scale reactors, which can coat several kilograms of powder. Several aspects of our FBRCVD approach are held to be proprietary by SRI, or have been patented (See, for example, U.S. Patents 5,149,514; 5,171,734; 5,227,195; 5,855,678).

One important feature of our experimental approach to particle coating is the use of temperature programmed reaction/desorption studies (TPR/TPD) to determine or define the particle surface chemistry before deposition to ensure that the particle coating reaction is heterogeneous, confined to the surface, thereby producing a conformal coating.

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Technical Contact:
Steven Crouch-Baker
(650) 859-2964
steven.crouch-baker@sri.com