Highly crystalline nanoscale phosphor particles and composite materials incorporating the particles

Abstract

Collections of phosphor particles have achieved improved performance based on improved material properties, such as crystallinity. Display devices can be formed with these improved submicron phosphor particles. Improved processing methods contribute to the improved phosphor particles, which can have high crystallinity and a high degree of particle size uniformity. Dispersions and composites can be effectively formed from the powders of the submicron particle collections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, sectional view of an embodiment of a laser pyrolysis apparatus, where the cross section is taken through the middle of a radiation path. The upper insert is a bottom view of a collection nozzle, and the lower insert is a top view of an injection nozzle.

FIG. 2 is a schematic, side view of an embodiment of a reactant delivery apparatus for the delivery of vapor reactants to the laser pyrolysis apparatus of FIG. 1.

FIG. 3A is a schematic, sectional view of an alternative embodiment of the reactant delivery apparatus for the delivery of an aerosol reactant to the laser pyrolysis apparatus of FIG. 1, the cross section being taken through the center of the apparatus.

FIG. 3B is a schematic, sectional view of a reactant delivery apparatus with two aerosol generators within a single reactant inlet nozzle.

FIG. 4 is a schematic sectional view of an inlet nozzle of a reactant delivery system for the delivery of both vapor and aerosol reactants in which the vapor and aerosol reactants combine within the nozzle.

FIG. 5 is a perspective view of an alternative embodiment of a laser pyrolysis apparatus.

FIG. 6 is a sectional view of an inlet nozzle of the alternative laser pyrolysis apparatus of FIG. 4, the cross section being taken along the length of the nozzle through its center.

FIG. 7 is a sectional view of an inlet nozzle of the alternative laser pyrolysis apparatus of FIG. 4, the cross section being taken along the width of the nozzle through its center.

FIG. 8 is a perspective view of an embodiment of an elongated reaction chamber for performing laser pyrolysis.

FIG. 9 is a perspective view of an embodiment of an elongated reaction chamber for performing laser pyrolysis.

FIG. 10 is a cut away, side view of the reaction chamber of FIG. 9.

FIG. 11 is a partially sectional, side view of the reaction chamber of FIG. 10, taken along line 11-11 of FIG. 9.

FIG. 12 is a fragmentary, perspective view of an embodiment of a reactant nozzle for use with the chamber of FIG. 9.

FIG. 13 is a schematic, sectional view of an apparatus for heat treating nanoparticles, in which the section is taken through the center of the apparatus.

FIG. 14 is a schematic, sectional view of an oven for heating nanoparticles, in which the section is taken through the center of a tube.

FIG. 15 is a sectional view of an embodiment of display device incorporating a phosphor layer.

FIG. 16 is a sectional view of an embodiment of a liquid crystal display incorporating a phosphor for illumination.

FIG. 17 is a sectional view of an electroluminescent display.

FIG. 18 is a sectional view of an embodiment of a flat panel display incorporating field emission display devices.

FIG. 19 is a sectional view of elements of a plasma display panel.

FIG. 20 is an x-ray diffractogram of a representative as-synthesized sample of YAlO₃ perovskite phase from laser pyrolysis.

FIG. 21 is a scanning electron micrograph of an as-synthesized sample with YAlO₃ perovskite phase from laser pyrolysis.

FIG. 22 is an x-ray diffractogram of a representative sample of Y₃Al₅O₁₂:Ce garnet (YAG) after a three step heat treatment.

FIG. 23 is an x-ray diffractogram of a representative sample of Y₃Al₅O₁₂:Ce garnet (YAG) after a three step heat treatment.

Claims

1. A collection of particles comprising a crystalline phosphor composition, the collection of particles having a number average primary particle size of no more than about 100 nm, a weight average secondary particle size of no more than about 250 nm and an crystallinity of at least about 90%.

2. The collection of particles of claim 1 wherein the number average primary particle size is no more than about 50 nm.

3. The collection of particles of claim 1 wherein the weight average secondary particle size is from about 50 nm to about 150 nm.

4. The collection of particles of claim 1 wherein effectively no primary particles have a diameter greater than about 5 times the average primary particle diameter.

5. The collection of particles of claim 1 wherein the primary particles have a diameter distribution such that at least about 95 percent of the particles have a diameter greater than about 40 percent of the average diameter and less than about 225 percent of the average diameter.

6. The collection of particles of claim 1 wherein the crystalline phosphor composition comprises a host lattice and a dopant from about 0.1 mole percent to about 20 mole percent.

7. The collection of particles of claim 6 wherein the dopant comprises a rare earth metal.

8. The collection of particles of claim 6 wherein the host lattice comprises a metal oxide or a metalloid oxide.

9. The collection of particles of claim 6 wherein the host lattice comprises yttrium aluminum garnet.

10. The collection of particles of claim 1 further comprising a surface modifier chemically bonded to the surface of the particle.

11. A liquid dispersion comprising the collection of particles of claim 1.

12. A composition comprising a monomer or a polymer, and the collection of particles of claim 1.

13. A method for the production of particles in a flowing reactor, the method comprises reacting a reactant flow to generate product particles within the flow in which the reactant flow comprises a heated aerosol wherein the heated aerosol is heated to a temperature at least about 10° C. greater than ambient temperature.

14. The method of claim 13 wherein the reaction is driven by a light beam that intersects the reactant flow, which comprises compositions that absorb light from the beam.

15. The method of claim 13 wherein the product particles have an average particle size of no more than about 500 nm.

16. A method for processing a collection of inorganic phosphor particles having an average particle size no more than about 250 nm, the method comprising heating the particle collection at a first temperature from about 250° C. to about 600° C. for 5 minutes to about five hours in an oxidizing atmosphere and a heating the particle collection in a reducing atmosphere for about 5 minutes to about 48 hours at a second temperature above the first temperature and sufficient to anneal the crystal structure of the particles while being at least above the transformation onset temperature of a desired phase and at least 100° C. below the melting temperature of the particles.

17. The method of claim 16 further comprising heating the particle collection at a third temperature below the third temperature and above the first temperature for five hours to 24 hours in a reducing atmosphere without causing significant sintering of the particles while increasing the crystallinity of the particles as determined by x-ray scattering.