GASEOUS REACTION PROCESS FOR THE PRODUCTION OF RARE EARTH OXYHALIDE AND OXIDE LUMINESCENT MATERIALS

• US 3,607,770 A
• Filed: 10/23/1968
• Issued: 09/21/1971
• Est. Priority Date: 10/23/1968
• Status: Expired due to Term

• Current Assignee: Jacob G. Rabatin
• Original Assignee: Jacob G. Rabatin
• Inventors: Rabatin, Jacob G.
• Primary Examiner(s): Edmonds, Robert D.
• Application Number:
  US04/780,928
• Time in Patent Office: 1,063 Days
• Field of Search: 252/301.4 23/87,15,19,21
• US Class Current: 252/301.40H
• CPC Class Codes: C01F 17/218 Yttrium oxides or hydroxides
• CPC Class Codes: C01F 17/224 Oxides or hydroxides of lanthanides
• CPC Class Codes: C01F 17/229 Lanthanum oxides or hydroxides
• CPC Class Codes: C01F 17/241 containing two or more rare earth metals, e.g. NdPrO3 or LaNdPrO3
• CPC Class Codes: C01P 2004/61 Micrometer sized, i.e. from 1-100 micrometer
• CPC Class Codes: C01P 2006/60 Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: C09K 11/777 Oxyhalogenides

Abstract

A method for the production of well-formed crystals of oxyhalides including oxychlorides, oxybromides, and oxyiodides, and oxides, of yttrium and the rare earth metals, i.e., elements having atomic numbers 39 and 57 through 71. Particles of the oxide of the selected element are heated in an atmosphere containing enough of the selected hydrogen halide to cause conversion of the oxide to the oxyhalide and recrystallization of the oxyhalide. This recrystallized oxyhalide can be converted to the corresponding oxide as large, well-crystallized particles by pyrohydrolysis. Alternatively, the oxyhalide can be formed by initially firing the oxide particles as a mixture with the selected ammonium halide. By starting with rare earth activated oxides, the process of the invention produces luminescent materials which are useful for cathode-ray tube applications, in lamps, and in X-ray applications such as in image converter tubes and film intensifier screens.

Claims

2. A process according to claim 1 in which the heating is performed within the temperature range of about 800* to about 1,200* C. in an atmosphere of the selected hydrogen halide mixed with a carrier gas selected from the group consisting of carbon dioxide, nitrogen and air.

3. A process according to claim 1 in which, prior to the step of claim 1:

said oxide particles are mixed with the ammonium halide whose halide is that of the selected oxyhalide and heated for at least about 1 hour at a temperature in the range of about 400* to 500* C. to convert said oxide particles to oxyhalide particles, and the step of claim 1 causes recrystallization of said oxyhalide particles.

4. A process according to claim 1 in which, subsequent to the step of claim 1:

said recrystallized oxyhalide particles are subjected to pyrohydrolysis to convert said oxyhalides to crystalline oxide particles.

5. A process according to claim 4 in which said pyrohydrolysis is performed in the temperature range of about 900* to 1,100* C.

6. A process according to claim 1 for the production of crystalline particles of luminescent materials wherein the oxyhalide also contains activator proportions of at least one element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, and Tm.

7. A process according to claim 3 for the production of crystalline particles of luminescent materials wherein the oxyhalide also contains activator proportions of at least one element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, and Tm.

8. A process according to claim 4 for the production of crystalline particles of luminescent materials wherein the oxyhalide also contains activator proportions of at least one element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, and Tm, activator proportions being carried over into said oxide crystals and causing said oxide crystals to be luminescent materials.

9. A process according to claim 1 in which said element is selected from the groups consisting of lanthanum, gadolinium, and yttrium. 10 A process according to claim 5 in which said luminescent material is terbium-activated lanthanum oxybromide.

11. A process according to claim 5 in which said luminescent material is terbium-activated lanthanum oxychlorde.

12. A process according to claim 4 wherein the luminescent material produced is gadolinium oxide activated with europium, the gaodlinium oxyhalide selected is gadolinium oxychloride, the formation of the gadolinium oxychloride is performed for about 1 to 4 hours in the temperature range of 400* to 500* C., the recrystallization is performed for about 1 to 4 hours in the temperature range of about 800* to 1,200* C. under a slightly oxidizing atmosphere, and the pyrohydrolysis converts the gadolinium oxychloride activated with europium to gadolinium oxide activated with europium.