Nano-scale metal oxide, oxyhalide and oxysulfide scintillation materials and methods for making same

• US 7,708,968 B2
• Filed: 03/26/2007
• Issued: 05/04/2010
• Est. Priority Date: 03/26/2007
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Srivastava, Alok, Stoklosa, Stanley John, Duclos, Steven Jude, Clothier, Brent Allen, Venkataramani, Venkat Subramaniam, Loureiro, Sergio Paulo Martins
• Primary Examiner(s): Mayes; Melvin C
• Assistant Examiner(s): Forrest; Michael
• Application Number:
  US11/728,445
• Publication Number:
  US 20080241041A1
• Time in Patent Office: 1,135 Days
• Field of Search: 106/286.6, 106/287, 106/287.18, 106/287.19, 977/773, 977/776, 977/775
• US Class Current: 423/263
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 13/328 by processes making use of emulsions, e.g. the kerosine process
• CPC Class Codes: C01F 17/241 containing two or more rare earth metals, e.g. NdPrO3 or LaNdPrO3
• CPC Class Codes: C01F 17/253 Halides
• CPC Class Codes: C01F 17/259 Oxyhalides
• CPC Class Codes: C01F 17/294 Oxysulfides
• CPC Class Codes: C01G 1/06 Halides
• CPC Class Codes: C01G 1/12 Sulfides
• CPC Class Codes: C01P 2002/54 one element only
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer

Abstract

Crystalline scintillator materials comprising nano-scale particles of metal oxides, metal oxyhalides and metal oxysulfides are provided. The nano-scale particles are less than 100 nm in size. Methods are provided for preparing the particles. In one method, used to form oxyhalides and oxysulfides, metal salts are dissolved in water, and then precipitated out as fine particles using an aqueous base. After the particles are separated from the solution, they are annealed under a flow of a water saturated hydrogen anion gas, such as HCl or H₂S, to form the crystalline scintillator particles. The other methods take advantage of the characteristics of microemulsion solutions to control droplet size, and, thus, the particle size of the final nano-particles. For example, in one method, a first micro-emulsion containing metal salts if formed. The first micro-emulsion is mixed with an aqueous base in a second micro-emulsion to form the final nano-scale particles.

Claims

1. A method for making nano-scale particles of an oxyhalide or oxysulfide type scintillation material, comprising:

forming a first micro-emulsion;

heating a solution, while adding the solution to the first micro-emulsion to form a second micro-emulsion;

forming precursor particles from the second emulsion; and

forming nano-scale particles of the oxyhalide or oxysulfide type scintillation material from the precursor particles.

2. The method of claim 1 wherein the solution comprises one or more organic metal salts comprising at least one metal anion selected from the group consisting of group 2 elements, group 3 elements, group 13 elements, group 14 elements, group 15 elements, and combinations thereof.

3. The method of claim 1 wherein the solution comprises one or more organic metal salts comprising at least one metal anion selected from the group consisting of lanthanum, cerium, terbium, thallium, and combinations thereof and a cation selected from the group consisting of —

OR, —

SR, and combinations thereof, wherein R is an alkyl group of one to twelve carbons.

4. The method of claim 1 wherein the solution comprises a first organic solvent, wherein the first organic solvent comprises at least one of a short-chain alkane, or an arene.

5. The method of claim 1 wherein forming the first micro-emulsion comprises

dissolving a surfactant in a second organic solvent to form a surfactant solution;

and

mixing an aqueous solution of an anion source with the surfactant solution to form the first micro-emulsion.

6. The method of claim 5 wherein the surfactant comprises at least one of an aromatic ethoxylate, a polyethylene glycol dodecyl ether, a sorbitan-fatty acid ester surfactant, a polyoxyethylenesorbitan fatty acid ester surfactant, or an alkyl phenol.

7. The method of claim 5 wherein the second organic solvent comprises at least one of a short-chain alkane, or an arene.

8. The method of claim 5 wherein the anion source comprises at least compound selected from the group consisting of NH₄I, NH₄F, NH₄Cl, NH₄Br, thioacetamide, thiourea, and combinations thereof.

9. The method of claim 1 wherein forming the nano-scale particles of the oxyhalide type scintillation material from the precursor particles comprises firing the precursor particles.

10. The method of claim 1 wherein the oxyhalide or oxysulfide type scintillation material comprises at least one phosphor having a general formula of LaO(I, Br, Cl, F):

Tb, Gd₂O₂S;

Tb, Gd₂O₂S;

Pr or combinations thereof.

11. The method of claim 1 wherein the nano-scale particles of the oxyhalide or oxysulfide type scintillator material are less than about 100 nm in size.