Oxygen-containing phosphor powders, methods for making phosphor powders and devices incorporating same

• US 6,180,029 B1
• Filed: 02/24/1998
• Issued: 01/30/2001
• Est. Priority Date: 02/24/1997
• Status: Expired due to Term

• Current Assignee: Sicpa Holding SA
• Original Assignee: Superior Micropowders LLC (Cabot Corporation)
• Inventors: Hampden-Smith, Mark J., Caruso, James, Kodas, Toivo T., Powell, Quint H., Skamser, Daniel J.
• Primary Examiner(s): KOSLOW, CAROL M
• Application Number:
  US09/028,603
• Time in Patent Office: 1,071 Days
• Field of Search: 423/592, 423/593, 423/263, 428/403, 902/7, 313/422, 313/467, 313/496, 313/503, 313/495, 313/582, 313/584, 283/92, 252/301.4 R, 252/301.4 S, 252/301.4 P, 252/301.6 R, 252/301.6 S, 252/301.6 P
• US Class Current: 252/301.40R
• CPC Class Codes: B01J 2/003 followed by coating of the granules to prevent the granules sticking together B01J2/30
• CPC Class Codes: B01J 2/006 Coating of the granules without description of the process or the device by which the granules are obtained to prevent the granules sticking together B01J2/30
• CPC Class Codes: B01J 2/02 by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
• CPC Class Codes: B01J 2/04 in a gaseous medium if combined with suspending the material in a gas, e.g. fluidised beds B01J2/16
• CPC Class Codes: B24B 37/044 characterised by the composition of the lapping agent
• CPC Class Codes: B42D 25/29 Securities; Bank notes
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 13/185 Preparing mixtures of oxides
• CPC Class Codes: C01B 17/20 Methods for preparing sulfides or polysulfides, in general ammonium sulfides or polysulfides C01C; sulfides or polysulfides of metals, other than alkali metals, magnesium, calcium, strontium and barium, see the relevant groups of subclasses C01F or C01G, according to the metal
• CPC Class Codes: C01G 15/006 Compounds containing, besides gallium, indium, or thallium, two or more other elements, with the exception of oxygen or hydrogen
• CPC Class Codes: C01G 23/003 Titanates C01G23/001 takes precedence
• CPC Class Codes: C01G 23/006 Alkaline earth titanates
• CPC Class Codes: C01G 25/00 Compounds of zirconium
• CPC Class Codes: C01P 2002/60 Compounds characterised by their crystallite size
• CPC Class Codes: C01P 2002/70 defined by measured X-ray, neutron or electron diffraction data
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/32 Spheres
• CPC Class Codes: C01P 2004/34 hollow
• CPC Class Codes: C01P 2004/50 Agglomerated particles
• CPC Class Codes: C01P 2004/52 highly monodisperse size distribution
• CPC Class Codes: C01P 2004/61 : Micrometer sized, i.e. from 1-100 micrometer
• CPC Class Codes: C01P 2004/62 : Submicrometer sized, i.e. from 0.1-1 micrometer
• CPC Class Codes: C01P 2004/80 : Particles consisting of a mixture of two or more inorganic phases
• CPC Class Codes: C01P 2006/10 : Solid density
• CPC Class Codes: C01P 2006/60 : Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: C01P 2006/80 : Compositional purity
• CPC Class Codes: C09D 11/03 : characterised by features other than the chemical nature of the binder
• CPC Class Codes: C09D 11/38 : characterised by non-macromolecular additives other than solvents, pigments or dyes
• CPC Class Codes: C09G 1/02 : containing abrasives or grinding agents abrasives as such C09K3/14; polishing of semi-conductors H01L
• CPC Class Codes: C09K 11/025 : non-luminescent particle coatings or suspension media
• CPC Class Codes: C09K 11/0805 : Chalcogenides
• CPC Class Codes: C09K 11/0877 : Borates
• CPC Class Codes: C09K 11/54 : containing zinc or cadmium
• CPC Class Codes: C09K 11/562 : Chalcogenides
• CPC Class Codes: C09K 11/565 : with zinc cadmium
• CPC Class Codes: C09K 11/567 : with alkaline earth metals
• CPC Class Codes: C09K 11/576 : with alkaline earth metals
• CPC Class Codes: C09K 11/584 : with zinc or cadmium
• CPC Class Codes: C09K 11/595 : with zinc or cadmium
• CPC Class Codes: C09K 11/623 : with zinc or cadmium
• CPC Class Codes: C09K 11/625 : with alkaline earth metals
• CPC Class Codes: C09K 11/642 : with zinc or cadmium
• CPC Class Codes: C09K 11/643 : with alkaline earth metals
• CPC Class Codes: C09K 11/644 : Halogenides C09K11/641 takes precedence
• CPC Class Codes: C09K 11/662 : with zinc or cadmium
• CPC Class Codes: C09K 11/666 : Aluminates; Silicates
• CPC Class Codes: C09K 11/671 : Chalcogenides
• CPC Class Codes: C09K 11/672 : with zinc or cadmium
• CPC Class Codes: C09K 11/7701 : Chalogenides
• CPC Class Codes: C09K 11/7708 : Vanadates; Chromates; Molybdates; Tungstates
• CPC Class Codes: C09K 11/7718 : with alkaline earth metals
• CPC Class Codes: C09K 11/7729 : Chalcogenides
• CPC Class Codes: C09K 11/7731 : with alkaline earth metals
• CPC Class Codes: C09K 11/7734 : Aluminates
• CPC Class Codes: C09K 11/77342 : Silicates
• CPC Class Codes: C09K 11/7746 : with alkaline earth metals
• CPC Class Codes: C09K 11/7769 : Oxides C09K11/7768 takes precedence
• CPC Class Codes: C09K 11/7771 : Oxysulfides
• CPC Class Codes: C09K 11/7774 : Aluminates
• CPC Class Codes: C09K 11/77742 : Silicates
• CPC Class Codes: C09K 11/7776 : Vanadates; Chromates; Molybdates; Tungstates
• CPC Class Codes: C09K 11/7784 : Chalcogenides
• CPC Class Codes: C09K 11/7786 : with alkaline earth metals
• CPC Class Codes: C09K 11/7787 : Oxides C09K11/7785 takes precedence
• CPC Class Codes: C09K 11/7789 : Oxysulfides
• CPC Class Codes: C09K 11/7797 : Borates
• CPC Class Codes: C09K 3/1436 : Composite particles, e.g. coated particles
• CPC Class Codes: C09K 3/1463 : Aqueous liquid suspensions
• CPC Class Codes: G21K 2004/06 : with a phosphor layer
• CPC Class Codes: G21K 4/00 : Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens photographic processes using X-ray intensifiers G03C5/17; discharge tubes comprising luminescent screens H01J1/62; cathode ray tubes for X-ray conversion with optical output H01J31/50
• CPC Class Codes: H01G 4/0085 : Fried electrodes
• CPC Class Codes: H01J 2211/42 : Fluorescent layers
• CPC Class Codes: H01J 29/085 : Anode plates, e.g. for screens of flat panel displays
• CPC Class Codes: H01J 29/20 : characterised by the luminescent material
• CPC Class Codes: H01L 21/3212 : by chemical mechanical polishing [CMP]
• CPC Class Codes: H01L 23/49883 : the conductive materials containing organic materials or pastes, e.g. for thick films for printed circuits H05K1/092
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 : Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/12044 : OLED
• CPC Class Codes: H01L 2924/3011 : Impedance
• CPC Class Codes: H05B 33/14 : characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: H05B 33/20 : characterised by the chemical or physical composition or the arrangement of the material in which the electroluminescent material is embedded
• CPC Class Codes: Y10S 462/903 : Security
• CPC Class Codes: Y10T 428/2991 : Coated
• CPC Class Codes: Y10T 428/2993 : Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]

Abstract

Phosphor powders and a method for making phosphor powders. The powders are oxygen-containing, such as metal oxides, silicates, borates or titanates and have a small particle size, narrow particle size distribution and are substantially spherical. The method of the invention advantageously permits the continuous production of such powders. The invention also relates to improved devices, such as display devices, incorporating the phosphor powders.

Claims

1. A powder batch comprising oxygen-containing phosphor particles, wherein said phosphor particles have a weight average particle size of from about 0.3 μ

m to about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size wherein said phosphor particles are substantially spherical and wherein said phosphor particles comprise a silicate host-material selected from the group consisting of zinc silicate, calcium silicate, barium silicate, gadolinium silicate and yttrium silicate.

2. A powder batch as recited in claim 1, wherein at least about 95 weight percent of said phosphor particles are not larger than twice said average particle size.

3. A powder batch as recited in claim 1, wherein at least about 90 weight percent of said phosphor particles are not larger than 1.5 times said average particle size.

4. A powder batch as recited in claim 1, wherein said average particle size is from about 0.3 μ

m to about 3 μ

m.

5. A powder batch as recited in claim 1, wherein said phosphor particles comprise at least a first activator ion.

6. A powder batch as recited in claim 1, wherein said phosphor particles comprise from about 0.02 to about 15 atomic percent of an activator ion.

7. A powder batch as recited in claim 1, wherein said phosphor particles have an average crystallite size of at least about 25 nanometers.

8. A powder batch as recited in claim 1, wherein said phosphor particles have an average crystallite size of at least about 40 nanometers.

9. A powder batch as recited in claim 1, wherein no greater than about 1 weight percent of said phosphor particles are in the form of hard agglomerates.

10. A powder batch as recited in claim 1, wherein said phosphor particles are coated particles comprising a coating on an outer surface thereof.

11. A powder batch comprising metal silicate phosphor particles, wherein said phosphor particles have a weight average particle size of from about 0.3 μ

m to about 5 μ

m.

12. A powder batch as recited in claim 11, wherein said metal silicates are selected from the group consisting of zinc silicate, calcium silicate, barium silicate, gadolinium silicate and yttrium silicate.

13. A powder batch as recited in claim 11, wherein said phosphor particles further comprise an activator ion selected from the group consisting of rare-earth elements and Mn.

14. A powder batch as recited in claim 11, wherein said phosphor particles have an average crystallite size of at least about 25 nanometers.

15. A powder batch as recited in claim 11, wherein said phosphor particles have an average crystallite size of at least about 40 nanometers.

16. A powder batch as recited in claim 11, wherein said phosphor particles are substantially spherical.

17. A powder batch as recited in claim 11, wherein said phosphor particles comprise an activator ion homogeneously distributed throghout said particles.

18. A powder batch as recited in claim 11, wherein said average particle size is from about 0.3 to about 3 μ

m.

19. A powder batch as recited in claim 11, wherein said phosphor particles further comprise an activator ion.

20. A powder batch as recited in claim 11, wherein said particles have a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size.

21. A powder batch comprising zinc oxide phosphor particles, wherein said zinc oxide phosphor particles have a weight average particle size of not greater than about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said phosphor particles are not larger than twice said average particle size.

22. A powder batch as recited in claim 21, wherein said phosphor particles further comprise Zn as an activator ion.

23. A powder batch as recited in claim 21, wherein said phosphor particles comprise crystallites having an average crystallite size of at least about 25 nanometers.

24. A powder batch as recited in claim 21, wherein said phosphor particles have an average crystallite size of at least about 40 nanometers.

25. A powder batch as recited in claim 21 wherein said phosphor particles are substantially spherical.

26. A powder batch as recited in claim 21, wherein said average particle size is from about 0.3 to about 3 μ

m.

27. A powder batch as recited in claim 21, wherein said phosphor particles further comprise an activator ion.

28. A powder batch comprising yttrium oxide phosphor particles, wherein said phosphor particles have a weight average particle size of from about 0.3 μ

m to about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size wherein said phosphor particles are substantially spherical and wherein said phosphor particles comprise an activator ion homogeneously distributed throughout said particles.

29. A powder batch as recited in claim 28, wherein said phosphor particles further comprise Eu as an activator ion.

30. A powder batch as recited in claim 28, wherein said phosphor particles have an average crystallite size of at least about 25 nanometers.

31. A powder batch as recited in claim 28, wherein said phosphor particles have an average crystallite size of at least about 40 nanometers.

32. A powder batch as recited in claim 28, wherein said average particle size is from about 0.3 to about 3 μ

m.

33. A powder batch as recited in claim 28, wherein said phosphor particles further comprise an activator ion.

34. A powder batch comprising barium aluminate phosphor particles, wherein said phosphor particles have a weight average particle size of from about 0.3 μ

m to about 5 μ

m.

35. A powder batch as recited in claim 34, wherein said phosphor particles comprise BaMgAl₁₄O₂₃.

36. A powder batch as recited in claim 34, wherein said phosphor particles further comprise Eu as an activator ion.

37. A powder batch as recited in claim 34, wherein said phosphor particles have an average crystallite size of at least about 25 nanometers.

38. A powder batch as recited in claim 34, wherein said phosphor particles have an average crystallite size of at least about 40 nanometers.

39. A powder batch as recited in claim 34, wherein said phosphor particles are substantially spherical.

40. A powder batch as recited in claim 34, wherein said phosphor particles comprise an activator ion homogeneously distributed throghout said particles.

41. A powder batch as recited in claim 34, wherein said average particle size is from about 0.3 to about 3 μ

m.

42. A powder batch as recited in claim 34, wherein said phosphor particles further comprise an activator ion.

43. A powder batch as recited in claim 34, wherein said particles have a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size.

44. A powder batch comprising oxygen-containing phosphor particles, wherein said phosphor particles have a weight average particle size of from about 0.3 μ

m to about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size and wherein said phosphor particles comprise at least a first coating consisting essentially of a metal on an outer surface thereof, and wherein said phosphor particles are substantially spherical.

45. A powder batch as recited in claim 44, wherein said average particle size is from about 0.3 μ

m to about 3 μ

m.

46. A powder batch as recited in claim 44, wherein said coating substantially encapsulates said phosphor particles.

47. A powder batch as recited in claim 44, wherein said coating is a substantially uniform non-particulate coating.

48. A powder batch as recited in claim 44, wherein said coating is a substantially uniform particulate coating.

49. A powder batch as recited in claim 44, wherein said coating has an average thickness of not greater than about 100 nanometers.

50. A powder batch as recited in claim 44, wherein said coating has an average thickness of from about 2 nanometers to about 10 nanometers.

51. A powder batch as recited in claim 44, wherein said phosphor particles further comprise a second coating substantially encapsulating said first coating.

52. A powder batch as recited in claim 44, wherein said phosphor particles comprise crystallites having an average crystallite size of at least about 25 nanometers.

53. A powder batch comprising composite oxygen-containing phosphor particles, wherein said composite phosphor particles have a weight average particle size of not greater than about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said particles are smaller than twice said average particle size and wherein said phosphor particles comprise at least a first oxygen-containing phosphor compound phase and at least a second phase dispersed throughout said first oxygen-containing phosphor compound.

54. A powder batch as recited in claim 53, wherein said second phase comprises a second oxygen-containing phosphor compound.

55. A powder batch as recited in claim 53, wherein said second phase comprises a metal sulfide phosphor compound.

56. A powder batch as recited in claim 53, wherein said particles are substantially spherical.

61. A method as recited in claim 55, wherein said heating step comprises passing said droplets through a heating zone having a temperature of from about 125°

C. to about 1500°

C.

57. A powder batch comprising yttrium gadolinium borate phosphor particles, wherein said phosphor particles have a weight average particle size of not greater than about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size.

58. A powder batch comprising phosphor particles having a titanate host material, wherein said phosphor particles have a weight average particle size of not greater than about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size.

59. A method for the production of oxygen-containing phosphor particles, comprising the steps of:

a) generating an aerosol of droplets from a liquid wherein said liquid comprises a oxygen-containing phosphor precursor and wherein said droplets have a size distribution such that at least about 70 weight percent of said droplets have a size of from about 1 μ

m to about 10 μ

m;

b) moving said droplets in a carrier gas; and

c) heating said droplets to remove liquid therefrom and form oxygen-containing phosphor particles.

60. A method as recited in claim 59, wherein said carrier gas comprises air.

62. A method as recited in claim 59, wherein said droplets have a size distribution such that no greater than about 20 weight percent of the droplets in said aerosol are larger than about twice the weight average droplet size.

63. A method as recited in claim 59, further comprising the step of removing a portion of droplets from said aerosol, said removed droplets having aerodynamic diameter greater than a preselected maximum diameter.

64. A method as recited in claim 59, further comprising the step of removing a second portion of said droplets from said aerosol, wherein said second portion of droplets have an aerodynamic diameter less than a preselected minimum diameter.

65. A method as recited in claim 59, wherein said liquid is a solution comprising a oxygen-containing phosphor precursor comprising a metal nitrate.

66. A method as recited in claim 59, further comprising the step of coating an outer surface of said oxygen-containing phosphor particles.

67. A method as recited in claim 66, wherein said coating is a metal oxide coating.

68. A method as recited in claim 66, wherein said coating is an organic coating.

69. A method as recited in claim 59, wherein said method further comprises the step of annealing said phosphor particles to increase the crystallinity of said particles.

70. A method for the production of coated oxygen-containing phosphor particles, comprising the steps of:

a) forming a liquid solution comprising an oxygen-containing phosphor precursor;

b) generating an aerosol of droplets from said liquid solution;

c) moving said droplets in a carrier gas;

d) removing at least a first portion of droplets from said aerosol wherein said droplets in said removed first portion have an aerodynamic diameter greater than a preselected maximum diameter;

e) heating said droplets to remove liquid therefrom and form particles comprising a oxygen-containing phosphor; and

f) coating an outer surface of said oxygen-containing phosphor particles by contacting said oxygen-containing phosphor particles with a volatile coating precursor.

71. A method as recited in claim 70, wherein said coating step comprises contacting said phosphor particles with a volatile coating precursor selected from the group consisting of metal chlorides, metal acetates and metal alkoxides.

72. A method as recited in claim 70, wherein said coating step comprises contacting said phosphor particles with a volatile coating precursor selected from the group consisting of silicon tetrachloride and aluminum trichloride.

73. A method as recited in claim 70, wherein said heating step comprises passing said droplets through a heating zone having a temperature of from about 125°

C. to about 1500°

C.

74. A method as recited in claim 70, wherein said phosphor particles have a particle density of at least about 80 percent of the theoretical density for said phosphor particles.

75. A method as recited in claim 70, wherein said aerosol droplets have an average size of from about 1 μ

m to about 5 μ

m and wherein not greater than about 20 weight percent of said droplets have a size greater than about twice said average droplet size.

76. A method as recited in claim 70, further comprising the step of removing a second portion of said droplets from said aerosol, wherein said droplets in said removed second portion have an aerodynamic diameter less than a preselected minimum diameter.

77. A method as recited in claim 70, wherein said oxygen-containing phosphor precursor is a metal nitrate.

78. A method as recited in claim 70, wherein said oxygen-containing phosphor precursor comprises a suspension of particulates.

79. A method as recited in claim 70, wherein said coating is a metal oxide.

80. A method as recited in claim 70, wherein said coating has an average thickness of not greater than about 100 nanometers.

81. A method as recited in claim 70, wherein said coating comprises a metal oxide.

83. A method as recited in claim 81, wherein said second phase comprises a second phosphor compound.

84. A method as recited in claim 81, wherein said second phase comprises a metal sulfide phosphor compound.

85. A method as recited in claim 81, wherein said second phase precursor comprises a particulate suspension.

97. A display device as recited in claim 76, wherein said weight average particle size is from about 0.3 μ

m to about 3 μ

m.

98. A display device as recited in claim 76, wherein said powder has a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size.

99. A display device as recited in claim 76, wherein said phosphor powder layers have an average thickness of not greater than about 3 times said average particle size.

100. A display device as recited in claim 76, wherein said phosphor powder layers have an average thickness of not greater than about 2 times said average particle size.

82. A method for the production of composite oxygen-containing phosphor particles, comprising of steps of:

a) forming a liquid solution comprising an oxygen-containing phosphor precursor and a second phase precursor;

b) generating an aerosol of droplets from said liquid solution;

c) moving said droplets in a carrier gas; and

d) heating said droplets to remove liquid therefrom and form composite oxygen-containing phosphor particles comprising an oxygen-containing phosphor compound and a second phase.

86. A method for the production of an oxygen-containing phosphor powder, comprising the steps of:

a) forming an aqueous-based solution comprising soluble precursors of an oxygen-containing phosphor;

b) generating an aerosol of droplets from said aqueous-based solution;

c) heating said droplets to form particles of an intermediate compound that is capable of being post-treated to form said oxygen-containing phosphor compound wherein said particles have a weight average particle size of not greater than about 5 μ

m; and

d) treating said intermediate compound to form said oxygen-containing phosphor powder.

87. A method as recited in claim 86, wherein said method further comprises the step of milling said phosphor powder.

88. A method as recited in claim 86, wherein said method further comprises the step of annealing said phosphor powder.

89. A method as recited in claim 86, wherein said method further comprises the step of annealing said phosphor powder in contact with an oxygen source.

90. A method as recited in claim 86, wherein said method further comprises the step of annealing said phosphor powder in contact with an oxygen-containing gas at a temperature and for a time sufficient to form said oxygen-containing phosphor powder.

91. A method as recited in claim 86, wherein said oxygen-containing phosphor is a ternary metal oxide.

92. A method as recited in claim 86, wherein said oxygen-containing phosphor is selected from the group consisting of yttrium aluminate and barium magnesium aluminate.

93. A method as recited in claim 86, wherein said oxygen-containing phosphor is a silicate.

94. A method for the production of an oxygen-containing phosphor powder selected from the group consisting of yttrium aluminate and barium magnesium aluminate, comprising the steps of:

a) forming an aqueous-based solution comprising soluble precursors of a said oxygen-containing phosphor;

b) generating an aerosol of droplets from said aqueous-based solution;

c) heating said droplets to form an intermediate compound that is capable of being post-treated to form said oxygen-containing phosphor compound; and

d) treating said intermediate compound to form said oxygen-containing phosphor powder.

95. A method for the production of an oxygen-containing phosphor powder comprising a silicate host material, comprising the steps of:

a) forming an aqueous-based solution comprising soluble precursors of a said oxygen-containing phosphor;

b) generating an aerosol of droplets from said aqueous-based solution;

c) heating said droplets to form an intermediate compound that is capable of being post-treated to form said oxygen-containing phosphor compound; and

d) treating said intermediate compound to form said oxygen-containing phosphor powder comprising a silicate host material.

96. A display device for conveying visual graphics and information, comprising:

a) a plurality of pixel regions comprising phosphor powder layers; and

b) an excitation source adapted to stimulate said phosphor powder to emit light to be viewed by a viewer;

wherein said phosphor powder comprises oxygen-containing phosphor particles consisting essentially of zinc oxide that are substantially spherical and have a weight average particle size of not greater than about 5 μ

m.

101. A display device for conveying visual graphics and information, comprising:

a) a plurality of pixel regions comprising phosphor powder layers; and

b) an excitation source adapted to stimulate said phosphor powder to emit light to be viewed by a viewer;

wherein said phosphor powder comprises silicate phosphor particles that are substantially spherical and have a weight average particle size of not greater than about 5 μ

m.

102. A display device for conveying visual graphics and information, comprising:

a) a plurality of pixel regions comprising phosphor powder layers; and

b) an excitation source adapted to stimulate said phosphor powder to emit light to be viewed by a viewer;

wherein said phosphor powder comprises borate phosphor particles that are substantially spherical and have a weight average particle size of not greater than about 5 μ

m.

103. A flat panel display, comprising:

a) an excitation source adapted to stimulate a phosphor; and

b) a viewing panel proximate to said excitation source, comprising a transparent substrate having disposed thereon an oxygen-containing phosphor powder defining pixels, wherein said phosphor powder comprises substantially spherical particles having a weight average particle size of not greater than about 10 μ

m and wherein said phosphor particles comprise a silicate host material selected from the group consisting of zinc silicate, calcium silicate, barium silicate, gadolinium silicate and yttrium silicate.

104. A flat panel display as recited in claim 103, wherein said weight average particle size is not greater than about 5 μ

m.

105. A flat panel display as recited in claim 103, wherein said weight average particle size is from about 0.3 μ

m to about 3 μ

m.

106. A flat panel display as recited in claim 103, wherein said powder has a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size.

107. A flat panel display as recited in claim 103, wherein said pixels comprise a phosphor powder layer having an average thickness of not greater than about 3 times said average particle size.

108. A flat panel display as recited in claim 103, wherein said pixels comprise a phosphor powder layer having an average thickness of not greater than about 2 times said average particle size.

109. A flat panel display as recited in claim 103, wherein said flat panel display is a field emission display.

110. A flat panel display as recited in claim 103, wherein said flat panel display is a plasma display.

111. A flat panel display, comprising:

a) an excitation source adapted to stimulate a phosphor;

b) a viewing panel proximate to said exitation source, comprising a transparent substrate having disposed thereon an oxygen-containing phosphor powder defining pixels,

wherein said phosphor powder comprises zinc oxide phosphor particles that are substantially spherical and have a weight average particle size of not greater than about 10 μ

m.

112. A field emission display, comprising:

a) a back plate portion comprising a plurality of electron tip emitters;

b) a transparent front plate portion comprising a layer of phosphor powder comprising oxygen-containing phosphor particles, wherein said phosphor particles have a weight average particle size of not greater than about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size wherein said particles are substantially spherical and wherein said phosphor particles comprise zinc oxide as a host material.

113. A field emission display as recited in claim 112, wherein said phosphor particles comprise crystallites having an average crystallite size of at least about 25 nanometers.

114. A field emission display as recited in claim 112, wherein said average particle size is from about 0.3 μ

m to about 3 μ

m.

115. A field emission display as recited in claim 112, wherein said phosphor particles are coated phosphor particles.

116. A field emission display as recited in claim 112, wherein said phosphor particles are coated phosphor particles comprising a metal oxide coating having a thickness of from about 1 to about 10 nanometers.

117. A field emission display as recited in claim 112, wherein said phosphor particles are coated phosphor particles comprising a metal oxide coating selected from the group consisting of aluminum oxide, silica, zinc oxide, tin oxide and indium oxide.

118. A field emission display as recited in claim 117, wherein said phosphor particles form a pixel layer having an average thickness of not greater than about 3 times said average particle size.

119. An electroluminescent device, comprising an electrically insulative substrate, a first electrode supported on said substrate, a phosphor layer disposed over said first electrode, a second electrode disposed over said phosphor layer, and means for applying an electric field between said first and second electrodes, wherein said phosphor layer comprises phosphor powder comprising oxygen-containing phosphor particles, wherein said phosphor particles are substantially spherical and have a weight average particle size of not greater than about 5 μ

m.

120. An electroluminescent device as recited in claim 119, wherein at least about 90 weight percent of said phosphor particles are not larger than twice said average particle size.

121. An electroluminescent device as recited in claim 119, wherein said average particle size is from about 0.3 to about 3 μ

m.

122. An electroluminescent device as recited in claim 119, wherein said phosphor particles comprise crystallites having an average crystallite size of at least about 25 nanometers.

123. An electroluminescent device as recited in claim 119, wherein said phosphor particles are composite particles.

124. A plasma display panel, comprising:

a) a rear panel comprising a plurality of row electrodes;

b) a front panel comprising a plurality of column electrodes, wherein said row electrodes and said column electrodes are in perpendicular relation to form a plurality of addressable x-y coordinates;

c) a phosphor powder dispersed on a substrate disposed between said electrodes, wherein said phosphor powder comprises particles having a weight average particle size of not greater than about 5 μ

m and a particle size distribution wherein at least about 90 weight percent of said particles are not larger than twice said average particle size wherein said particles are substantially spherical and wherein said phosphor particles comprise an oxygen-containing host material selected from the group consisting of yttrium gadolinium borate and zinc silicate.

125. A plasma display panel as recited in claim 124, wherein said average particle size is from about 0.3 μ

m to about 3 μ

m.

126. A plasma display panel as recited in claim 124, wherein said phosphor particles comprise crystallites having an average crystallite size of at least about 25 nanometers.

127. A plasma display panel as recited in claim 124, wherein said phosphor powder is dispersed in a layer having an average thickness of not greater than about three times said average particle size.