US4783596A — Solid state scintillator and treatment therefor

Claim 1

Independent Claim 197 words

A polycrystalline X-ray stimulable scintillator body comprising a sintered rare earth doped gadolinia and yttria ceramic having a cubic crystal structure which has received a controlled oxidation anneal to reduce radiation damage otherwise occurring when said scintillating body is exposed to X-ray radiation during conversion of said X-ray radiation to a display image, the composition of said ceramic comprising from about 5 mole percent to about 50 mole percent Gd 2 O 3 , between about 0.5 and 12 mole percent of a rare earth activator oxide selected from the group consisting of Eu 2 O 3 and Nd 2 O 3 , and between about 0.0001 and 0.5 mole percent of at least one afterglow reducer selected from the group of Pr 2 O 3 and Tb 2 O 3 , the remainder of said composition being Y 2 O 3 , said controlled oxidation anneal being effected from about 1000° C. up to about 1500° C. at an oxygen partial pressure in the range from about 10 -4 up to about 10 -2 atmosphere, said scintillator body exhibiting a smaller efficiency loss when exposed to X-ray radiation than said body absent said controlled oxidation anneal.

Claim 2

Dependent Claim 197 words

A polycrystalline X-ray stimulable scintillator body comprising a sintered rare earth doped gadolinia and yttria ceramic having a cubic crystal structure which has received a controlled oxidation anneal to reduce radiation damage otherwise occurring when said scintillating body is exposed to X-ray radiation during conversion of said X-ray radiation to a display image, the composition of said ceramic comprising from about 5 mole percent to about 50 mole percent Gd 2 O 3 , between about 0.5 and 12 mole percent of a rare earth activator oxide selected from the group consisting of Eu 2 O 3 and Nd 2 O 3 , and between about 0.0001 and 0.5 mole percent of at least one afterglow reducer selected from the group of Pr 2 O 3 and Tb 2 O 3 , the remainder of said composition being Y 2 O 3 , said controlled oxidation anneal being effected from about 1000° C. up to about 1500° C. at an oxygen partial pressure in the range from about 10 -4 up to about 10 -2 atmosphere, said scintillator body exhibiting a smaller efficiency loss when exposed to X-ray radiation than said body absent said controlled oxidation anneal.

Claim 3

Dependent Claim 18 words

A scintillator body as in claim 1 wherein said controlled anneal is conducted in air at subatmospheric pressures.

Claim 4

Dependent Claim 28 words

A scintillator body as in claim 2 wherein the subatmospheric air pressure is maintained in the range from about 5×10 -7 atmosphere up to about 1.5×10 -1 atmosphere.

Claim 5

Dependent Claim 19 words

A scintillator body as in claim 1 wherein the rare earth activator oxide is Eu 2 O 3 .

Claim 6

Dependent Claim 28 words

A scintillator body as in claim 1 wherein the ceramic contains other metal ions selected from zirconium, hafnium, thorium, and tantalum to serve as transparency promoting densifying agents.

Claim 7

Dependent Claim 40 words

A scintillator body as in claim 5 wherein the ceramic still further contains at least one light output receiver selected from CaO and SrO in an amount sufficient to effect a higher light output than said ceramic absent said restorers.

Claim 8

Independent Claim 203 words

A method for preparing a polycrystalline x-ray stimulable scintillator body which is more resistent to radiation damage comprising the steps of: (a) sintering a rare earth doped gadolina containing a metal oxide compact to form a dense ceramic body having a cubic crystal structure, the composition of said ceramic body comprising from about 5 mole percent up to about 50 mole percent Gd 2 O 3 , between about 0.5 and 12 mole percent of a rare earth activator oxide selected from the group consisting of Eu 2 O 3 and Nd 2 O 3 , and between about 0.0001 and 0.5 mole percent of at least one afterglow reducer selected from the group consisting of Pr 2 O 3 and Tb 2 O 3 , the remainder of said composition being Y 2 O 3 , and (b) annealing said ceramic body in a controlled oxygen containing atmosphere, said controlled oxidation anneal being effected from about 1000° C. up to about 1500° C. at an oxygen partial pressure in the range from about 10 -4 up to about 10 -2 atmosphere, said ceramic body exhibiting a smaller efficiency loss when exposed to X-ray radiation than said body absent said controlled oxidation anneal.

Claim 9

Independent Claim 203 words

A method for preparing a polycrystalline x-ray stimulable scintillator body which is more resistent to radiation damage comprising the steps of: (a) sintering a rare earth doped gadolina containing a metal oxide compact to form a dense ceramic body having a cubic crystal structure, the composition of said ceramic body comprising from about 5 mole percent up to about 50 mole percent Gd 2 O 3 , between about 0.5 and 12 mole percent of a rare earth activator oxide selected from the group consisting of Eu 2 O 3 and Nd 2 O 3 , and between about 0.0001 and 0.5 mole percent of at least one afterglow reducer selected from the group consisting of Pr 2 O 3 and Tb 2 O 3 , the remainder of said composition being Y 2 O 3 , and (b) annealing said ceramic body in a controlled oxygen containing atmosphere, said controlled oxidation anneal being effected from about 1000° C. up to about 1500° C. at an oxygen partial pressure in the range from about 10 -4 up to about 10 -2 atmosphere, said ceramic body exhibiting a smaller efficiency loss when exposed to X-ray radiation than said body absent said controlled oxidation anneal.

Claim 10

Dependent Claim 17 words

A method as in claim 7 wherein said controlled anneal is conducted in air at subatmospheric pressure.

Claim 11

Dependent Claim 27 words

A method as in claim 8 wherein said subatmospheric air pressure is maintained in the range from about 5×10 -7 atmosphere up to about 1.5×10 -1 atmosphere.

Claim 12

Dependent Claim 15 words

A method as in claim 7 wherein the sintering action is achieved by hot pressing.

Claim 13

Dependent Claim 20 words

A method as in claim 7 wherein the rare earth activator oxide is europium oxide (Eu 2 O 3 ).

Claim 14

Dependent Claim 31 words

A method as in claim 7 wherein said metal oxide compact still further contains other metal ions selected from zirconium, hafnium, thorium and tantalum to serve as transparency promoting densifying agents.

Claim 15

Dependent Claim 42 words

A method as in claim 12 wherein said metal oxide compact still further contains at least one light output restorer selected from CaO and SrO in an amount sufficient to effect a higher light output than said scintillator body absent said restorer.

Claim 16

Dependent Claim 224 words

In a radiographic imaging system utilizing an X-ray source, a scintillator body to convert the X-rays to an optical image, and photodetection means coupled thereto for converting said optical image to an electronic display thereof, the improvement wherein said scintillator body comprises a polycrystalline sintered rare earth doped gadolinia containing ceramic having a cubic crystal structure which has received a controlled oxidation anneal to reduce radiation damage otherwise occurring when said scintillator body is exposed to said X-rays, the composition of said ceramic comprising from about 5 mole percent up to about 50 mole percent Gd 2 O 3 , between about 0.5 and 12 mole percent of a rare earth activator oxide selected from the group consisting of Eu 2 O 3 and Nd 2 O 3 , and between about 0.0001 and 0.5 mole percent of at least one afterglow reducer selected from the group consisting of Pr 2 O 3 and Tb 2 O 3 , the remainder of said composition being Y 2 O 3 , said controlled oxidation anneal being effected from about 1000° C. up to about 1500° C. at an oxygen partial pressure in the range from about 10 -4 up to about 10 -2 atmosphere, said scintillator body exhibiting a smaller efficiency loss when exposed to X-ray radiation than said body absent said contolled oxidation anneal.

Claim 17

Dependent Claim 224 words

In a radiographic imaging system utilizing an X-ray source, a scintillator body to convert the X-rays to an optical image, and photodetection means coupled thereto for converting said optical image to an electronic display thereof, the improvement wherein said scintillator body comprises a polycrystalline sintered rare earth doped gadolinia containing ceramic having a cubic crystal structure which has received a controlled oxidation anneal to reduce radiation damage otherwise occurring when said scintillator body is exposed to said X-rays, the composition of said ceramic comprising from about 5 mole percent up to about 50 mole percent Gd 2 O 3 , between about 0.5 and 12 mole percent of a rare earth activator oxide selected from the group consisting of Eu 2 O 3 and Nd 2 O 3 , and between about 0.0001 and 0.5 mole percent of at least one afterglow reducer selected from the group consisting of Pr 2 O 3 and Tb 2 O 3 , the remainder of said composition being Y 2 O 3 , said controlled oxidation anneal being effected from about 1000° C. up to about 1500° C. at an oxygen partial pressure in the range from about 10 -4 up to about 10 -2 atmosphere, said scintillator body exhibiting a smaller efficiency loss when exposed to X-ray radiation than said body absent said contolled oxidation anneal.

Claim 18

Dependent Claim 20 words

A radiographic imaging system as in claim 14 wherein the rare earth activator oxide is Eu 2 O 3 .

Claim 19

Dependent Claim 29 words

A radiographic imaging system as in claim 14 wherein the ceramic further contains other metal ions selected from zirconium, thorium and tantalum to serve as transparency promoting densifying agents.

Claim 20

Dependent Claim 41 words

A radiographic imaging system as in claim 16 wherein the ceramic still further contains at least one light output restorer selected from CaO and SrO in an amount sufficient to effect a higher light output than said ceramic absent said restorers

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-11-08	1992-05-09	1992-11-08	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-11-08	1996-05-09	1996-11-08	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-11-08	2000-05-09	2000-11-08	$7700.00	Window Closed / Lapsed

Solid state scintillator and treatment therefor

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