CA1041288A - Cerium-activated yttrium silicate phosphor - Google Patents
Cerium-activated yttrium silicate phosphorInfo
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- CA1041288A CA1041288A CA193,868A CA193868A CA1041288A CA 1041288 A CA1041288 A CA 1041288A CA 193868 A CA193868 A CA 193868A CA 1041288 A CA1041288 A CA 1041288A
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
- C09K11/7706—Aluminates
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
- C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
- C09K11/77742—Silicates
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Abstract
CERIUM-ACTIVATED YTTRIUM SILICATE PHOSPHOR
Abstract of the Disclosure In the firing of a cerium-activated Y2O3-SiO2 system phosphor, addition of BaF2 increases the luminosity and/or emission intensity of the phosphor. This novel phosphor is easily prepared by firing a mixture of Y2O3, SiO2, CeO2 and BaF2.
Abstract of the Disclosure In the firing of a cerium-activated Y2O3-SiO2 system phosphor, addition of BaF2 increases the luminosity and/or emission intensity of the phosphor. This novel phosphor is easily prepared by firing a mixture of Y2O3, SiO2, CeO2 and BaF2.
Description
This invention relates to an improvement in cerium-activated yttrium silicate phosphor of fast decay type.
Fast decay phosphDrs have important rDles as phosphors for flying spot scanner tubes for EVR ~Electric Video Recording) and index color tubes for information processing. In such flying ~pot scanner tubes~ unlike television picture tubes, a spot on the luminous screen is not modulated, but is of constant luminosity and only scans at very high speed. The light fro~ such flying spot is converged through an optical system, and scans a picture or pattern on a film or sheet, and the light passing through the film or reflected from the sheet is transformed into a time-~equential elec~ric signal.
For light source of such flying spot, fast decaying characteristic is an important factor. Also for some uses, ~ the spectrum distribution is an important characteristic. For -~ ~ irlstance, for obtaining an eIectric signal of a color film, the flying spot source should have a spectrum dis~ribution to cover ~ threa principal colors in order to make three electric signals `l ~ corresponding to the principal colors. Furthermore, ~hen scan-ni~g a monochromic (e.g. black-a~d-white) pic~ure or~pattern, a ~igh luminosity is preferable for monitoring with the naked eye.
It has been known that cerium activated phosphors for ~nstance, Ca2MgSiO7:Ce, Ca2A12SiO7:Ce, YP04:Ge, Y3(Al,Ga)5012:Ce, Y2SiO5:Ce, Y2SiO7:Ce, have fast decaying emission at electron beam exci~ation. However, these phosphors, except Y3(Al,Gaj5012:Ce whlch emits yellow light, emit only near-ultraviolet light or near-ultraviolet blue light, and are not satisfactory as a phosphor of a color fly~ng spot tube, nor even as a blue emitting phosphor component of a white light flying spot eube.
-1(~43~Z~8 In 1969, A.H. Gomes and A. Brill reported on Ce-acti-vated yttrium silicate.s, Y2SiO5:Ce and Y2Si207:Ce.
The Y2Si207:Ce phosphor has the peak emission at around 380 nm, and has the highest energy-converting efficiency among the ~;
abovementioned Ce-activated phosphors.
~' The Y2SiO5:Ce phosphor has the second high energy con-version efficiency, and the peak in the spectrum curve is at `~ around 400 nm.
These Ce-activated yttrium silicate phosphors have been made by firing a mixture of oxides of component materials in air :
or a reducing atmosphere. In the firing of these phosphors, as ~ mlneralizer or flux for accelerating a reaction, YF3 (yttrlum ;/ fluoride) was conventionally used, but it was difficult to obtain a single composition of ~Y2Si207:Ce, that is, consisting only of -phase composition excluding components of other phases.
It is the object of this invention to provide novel Ce-activated yttrium silicate phosphors having improved charac-i" ~ teristics.
According to the invention, an improved phosphor is Z0 obea~lDed by firing a mixture of Y203, SiO2~ CeO2 and BaF2- The ~ nvention is based on the empirical finding that luminosity of ;~ Y25iO5:Ce phosphor is greatly improved when the mixed materials are~fired~with the addition of BaF2 0nd that the single compo-- ~ sition ~-Y2Si207 is easily obtained, resulting in improved emission intensity (hereinafter defined as the value of the height of the peak).
More precisely, the present invention relates to a phosphor which is the fired reaction product of a mixture of Y203, SiO2, CeO2, and BaF2, the mol ratio of SiO2 to Y203 in the mixture being represented by a formula of SiO2 /
Y203 - X where 1.-0~X~1.2 and the mol ratio of BaF2 to Y203 A~ ' `` 1(~4~8~1 in the mixturebeingrepresented by a formula BaF2/Y203 = Y
where 0.01< Y< 0.2 for Y2SiO5 : Ce phosphor or the mol rat$o of SiO2 to Y203 being represented by a formula SiO2/Y203 = X' where 2.0_ X'< 2.5 and the mol ratio of BaF2 to Y203 in the mixture being represented by the formula BaF2/Y203 = Y' where 0.01< Y< 0.1 and whose crystallogical designation is ~-pyrosilicate for Y2Si207 : Ce phosphor.
Certain preferred features of the invention are illustrated by the attached drawings in which :
~; 10 Fig. 1 shows spectrum distributions of emission of -~: Y2SiO5 : Ce phosphors at electron beam excitation, whereln curve "a" indicates the phosphor made by Example I and curve "b"
'~
: ~
: ~ , ..... . .
1~ 8 indicates the phosphor made by conventional method and mater~als, ; Fig. 2 shows a relation between relative luminosity and amount of BaF2 added in firing ~2SiO5:Ce.
Flg. 3 ~hows a re]ation between relative e~ission intensity (herein defined as the value of peak height in the emission spec~rum curve) and amount of BaF2 added in firing Y2Si5-Ce- and Fig. 4 shows a relation between relative emission ~- intensity (defined as above) and amount of BaF2 added in firing-Y2Si2O7:Ce.
Among yttrium silicates as host (or ma~r~x) of phosphor, ;
` ~2SiO5 (namely, SiO2/Y203=1) and ~ and ~ phases of Y2Si207 (namely, SiO2/Y203=2) are known. The present invention applies particularly to Y2SiO5 and Y2Si207.
The s~oichiometric mol ratio of ~he component materials ;~ 2 2 3 2/Y203_1 for Y2SiO5 phosphor, and SiO /Y 0 =2 for Y2Si207 phosphor. However, in actual systhesis of ~he phos-; phor, ~tha ratio SiO2/Y203 should be l.0 - 1.2, more preferably 1.2 for Y2SiO5 phosphor, and 2.0 - 2.5, more preferably 20 2.2 - 2.5 for Y2Si207 phosphor. It ~as found through analysis by powder X-ray diffraction than an excessive amount o~ SiO2 makes the synthesls easier resulting in higher lumiDous-efficiency.
Certain preferred embodlments of the invention are illustrated by the attached dra~ings in which:
Fig. 1 sho~s spectrum distributions of emission of Y2SiO~:Ce phosphors at electron beam excitation, wherein curve "a" i~dicates the phosphor made by Example I and curve "b" indica~es the phosphor made by conventional method and materials, Fig. 2 shows a relation between relative luminosity and amount of BaF2 added in firing Y2SiO5:Ce, _ 4 ---F~g. 3 shows a relation between relative emission intensity (herein defined as the value of peak heigh~ in the - emission spectrum curve~ and amount of BaF2 ~dded in firing Y2SiO5:
Ce, and Fig. 4 shows a relation between relative emission inten-sity (defined as above) and amount of BaF2 added in firing Y2Si207:Ce.
The effect of amount of BaF2 added in firing , Y2SiO5:Ce phosphor is sho~n in Fig. 2 and Fig. 3, wherein addition of BaF2 in an amoun~ of 0~01 - 0.2 mol per 1 mol of the Y2SiO5:Ce .
phosphor causes the abovementioned improved effect, and the preferable range ls 0.03 - 0.1 mol per l-mol of the phosphor, and further, the highes~ luminosity and the highest peak value of ;~ emission intensi~y are attained in the optimum range of 0.05 -0.07 mol per 1 mol of the phosphor. For the abovementioned aptimum ;~ range of BaF2, the peak value of the luminosity of the present phosphor is 160% and ~hat of the emission intensity of the same is ;~; l10% ln~comparison~with those values of the conventional Y2SiO5:Ce p~osphor fired with YF3 addition.
20 ~ The effect of amou=t ~of BaF2 added in firi=g Y2Si2O7:Ce ph~osphor is~shown in Fig. 4, wherein addition of DaF2 in an amoune of 0.01 -~O.l mol per l mol of the Y25i2O7:Ce phosphor~ causes the abovementioned improved effect, aDd the preferable range is in an amount of 0.03 - 0.08 mol per l mol of the phosphor, and further, the highest peak value of emission inte=sity i8 attain~d at around the optimum amount of approxi=ately 0.05 mol per 1 mol of ~he phosphor.
For the abovementioned optimum amount of BaFzp the peak value of the emisslon intensity of the present phosphor is 150 to 160% in comparison with the value of ~he conventional Y2Si207:Ce ` 1~4: L2~3~
phosphor fired without BaF .
Analysis by powder X-ray diffraction does not clearly `~ show imperfection of la~tice constant which indicates production of barium silicate or intermixing of barium ions in the la~tice.
~` Many additives, for instance, fl~oride compounds, such as AlF3, MgF29 CaF2, SrF2, LiF, ZnF2, and also compounds of barium, such as BaC03, Ba(N03j2, BaC12, have been tested as mineralizer or flux in firing the Y2SiO5 and Y2Si207 phosphors. ~mong the above-me~tioned tested compounds, none ~as found to improve the lumino-sities or emissi~n intensities of the phosphors.
Prom the abo~ementioned facts, the principle of the improvement can be hypothetically elucidated as follows:
The improvement in Y2Si207:Ce phosphor is supposed to be caused by the effect of BaF2 as mineralizer. While the improvement in Y2S105:Ce is supposed to be caused by the increase of emission - i~tenslty at around 450 nm wavelength (as shown by curve "a" of Fig. 1) where specific visual sensitivity of the eye is high, this improvement is attained presumably not only by the function of BaF2 as ~ineralizer, but also by some intangible contribution of barium . 20~ to improvement of the emission. However, the importance is in that uch improvement is effected by addition of BaF2 only, and not by other substance.
In ~he firing of the Y2SiO5:Ce phosphor, firing at a temperature of 1200 - 1500 C in air or a slightly reducing atmos--:- :
~ phere for 3 hours gives a good result. The emissio~ intensity, - hereln defined as, the value of the peak height in the emission spectrum curvej is the highest when ~he firing is made at around .
~ 1300 C, but the firing temperature to give the peak of the emission `~:
` intensity is dependent on concentration of cerium. For instance, when 0.01 mol of Ce is added to l mol of phosphor, the peak is obtained by firing at around 1300 C.
~04~;288 Between the abovementioned two firlng conditions, the latter one, namely, firing at 1400C with the 0.03 mol Ce addition to 1 mol phosphor results in a lit~le higher luminosity, but in a lower peak value of emission intenslty.
An analysis by powder X-ray diffraction proved that a ~lring at over 1200C for 3 hours formed Y2SiO5 compound.
In the firing of the Y2Si207 phosphor, firing at a tem-perature of 1260 to 1430C in air or a slightly reducing atmosphere for 3 to 4 hours makes a good result. Since the transition tempera-ture from ~-Y2Si207 to a-Y2Si207 or to y-Y2Si207 compound is 1250 C
+ 10C or 1445C + 10C, respectively, the firing should be done a~ a temperature between 1260C and 1430 C.
In the below-mentioned examples, 99.~99~ pure Y203 9 99.999 pure YF3 and 99.9% pure CeO2 manufactured by Shinetsu Chemical Co., Ltd. of Japan, 99.999% pure SiO2 manufactured by Mathey ~ Co., Ltd. of England and ultrapure BaF2 manufactured by E. Merk AoG~
of German Federal Republic are used as the ~tarting material~.
In ~he measurement of the luminosity, ~he calibrations for relative luminosity curve are made by using a Xodak Wratten ~ (Trade Mark)~Mo. 106 fil~er and a photomultiplier of S-4 spectrum sensitivity.
Example I
In this Example a phosphor is made from:
Yttrium oxide ~Y203) ....................... 73.02 gr Anhydrous silicon oxide (SiO2) ............. 23~7S gr Cerium oxide ~CeO2) ....................... 3.44 gr Barium Fluoride ~BaF2) .................... 2.89 gF
The abovementioned starting materials are powdered and mixed well in a bowl, and ~hen the mixture is placed in a platinum boat and heated in air at 1300 C for 3 hours.
l~ Z8~3 An analysis by powder X-ray diffraction proved that the phosphor made in this manner consisted mainly of Y2SiO5:Ce. The spectrum distribution of this phosphor is shown in Fig. 1 by curve "a". The peak value of the spectrum curve of this phosphor is al- ;
most equal to known phosphor of Y2Si205:Ce that is fired with YF3 as mineralizer, and its luminosity is as high as 160~ of that of the abovementioned known phosphor.
Example II
~' The starting materials of Example I are powdered and mixed well in a bowl, and then the mixture is placed in an alumina boat , ~ .
~`~ and heated at 1400C for 3 hours in a slightly reducing atmosphere .~
of argon gas containing 5% hydrogen.
The phosphor made in this manner has a luminosity as high as 138% and the emission intensity at its peak as~high as 110%, co~pared with those of the abovementioned known Y2SiO5:Ce phosphor that is fired without BaF2.
Example III
In this Example a phosphor is made ~rom:
Yttrium oxite (Y203) ....l................... 223.58 gr Anhydrous silicon dioxide (SiO2) .,.......... 144.Zl gr Cerium oxide (CeO2~ ......................... 3.44 gr Barium Fluoride~SBaF2) .. ; 8.76 gr The abovementioned starting materials are powdered and mixed-well in a bowl. Then the mixture is placed in a platinu~
boat and heated in air at 1350C for 1 hour. The product is again po~dered and mixed in a bowl and heated at 1350C for 2 hours. An analysis by powder X-ray diffraction proved that the phosphor made in this manner consisted of Y2Si207:Ce. The peak value of ~; the spectrum curve of this phosphor is as high as 150 of that of 30 the conventional Y2Si207:Ce phosphor that: i~ fired without BaF2. `~
.
Example IV
The starting materials of the Example III are powdered and mixed well in a bowl, and then the mix~ure ls placed in a graphite boat and heated at 1350C for 3 hours in a slightly reducing atmosphere of argon gas containing 5% hydrogen. The phosphor made in this manner has an emission intensity at its peak as high 2S 150~ of that of the abovementioned known Y2Si207:Ce phosphor that ls fired wltho~t BaF2.
::
, :
.
, ~, ,: .
', .
~ :
Fast decay phosphDrs have important rDles as phosphors for flying spot scanner tubes for EVR ~Electric Video Recording) and index color tubes for information processing. In such flying ~pot scanner tubes~ unlike television picture tubes, a spot on the luminous screen is not modulated, but is of constant luminosity and only scans at very high speed. The light fro~ such flying spot is converged through an optical system, and scans a picture or pattern on a film or sheet, and the light passing through the film or reflected from the sheet is transformed into a time-~equential elec~ric signal.
For light source of such flying spot, fast decaying characteristic is an important factor. Also for some uses, ~ the spectrum distribution is an important characteristic. For -~ ~ irlstance, for obtaining an eIectric signal of a color film, the flying spot source should have a spectrum dis~ribution to cover ~ threa principal colors in order to make three electric signals `l ~ corresponding to the principal colors. Furthermore, ~hen scan-ni~g a monochromic (e.g. black-a~d-white) pic~ure or~pattern, a ~igh luminosity is preferable for monitoring with the naked eye.
It has been known that cerium activated phosphors for ~nstance, Ca2MgSiO7:Ce, Ca2A12SiO7:Ce, YP04:Ge, Y3(Al,Ga)5012:Ce, Y2SiO5:Ce, Y2SiO7:Ce, have fast decaying emission at electron beam exci~ation. However, these phosphors, except Y3(Al,Gaj5012:Ce whlch emits yellow light, emit only near-ultraviolet light or near-ultraviolet blue light, and are not satisfactory as a phosphor of a color fly~ng spot tube, nor even as a blue emitting phosphor component of a white light flying spot eube.
-1(~43~Z~8 In 1969, A.H. Gomes and A. Brill reported on Ce-acti-vated yttrium silicate.s, Y2SiO5:Ce and Y2Si207:Ce.
The Y2Si207:Ce phosphor has the peak emission at around 380 nm, and has the highest energy-converting efficiency among the ~;
abovementioned Ce-activated phosphors.
~' The Y2SiO5:Ce phosphor has the second high energy con-version efficiency, and the peak in the spectrum curve is at `~ around 400 nm.
These Ce-activated yttrium silicate phosphors have been made by firing a mixture of oxides of component materials in air :
or a reducing atmosphere. In the firing of these phosphors, as ~ mlneralizer or flux for accelerating a reaction, YF3 (yttrlum ;/ fluoride) was conventionally used, but it was difficult to obtain a single composition of ~Y2Si207:Ce, that is, consisting only of -phase composition excluding components of other phases.
It is the object of this invention to provide novel Ce-activated yttrium silicate phosphors having improved charac-i" ~ teristics.
According to the invention, an improved phosphor is Z0 obea~lDed by firing a mixture of Y203, SiO2~ CeO2 and BaF2- The ~ nvention is based on the empirical finding that luminosity of ;~ Y25iO5:Ce phosphor is greatly improved when the mixed materials are~fired~with the addition of BaF2 0nd that the single compo-- ~ sition ~-Y2Si207 is easily obtained, resulting in improved emission intensity (hereinafter defined as the value of the height of the peak).
More precisely, the present invention relates to a phosphor which is the fired reaction product of a mixture of Y203, SiO2, CeO2, and BaF2, the mol ratio of SiO2 to Y203 in the mixture being represented by a formula of SiO2 /
Y203 - X where 1.-0~X~1.2 and the mol ratio of BaF2 to Y203 A~ ' `` 1(~4~8~1 in the mixturebeingrepresented by a formula BaF2/Y203 = Y
where 0.01< Y< 0.2 for Y2SiO5 : Ce phosphor or the mol rat$o of SiO2 to Y203 being represented by a formula SiO2/Y203 = X' where 2.0_ X'< 2.5 and the mol ratio of BaF2 to Y203 in the mixture being represented by the formula BaF2/Y203 = Y' where 0.01< Y< 0.1 and whose crystallogical designation is ~-pyrosilicate for Y2Si207 : Ce phosphor.
Certain preferred features of the invention are illustrated by the attached drawings in which :
~; 10 Fig. 1 shows spectrum distributions of emission of -~: Y2SiO5 : Ce phosphors at electron beam excitation, whereln curve "a" indicates the phosphor made by Example I and curve "b"
'~
: ~
: ~ , ..... . .
1~ 8 indicates the phosphor made by conventional method and mater~als, ; Fig. 2 shows a relation between relative luminosity and amount of BaF2 added in firing ~2SiO5:Ce.
Flg. 3 ~hows a re]ation between relative e~ission intensity (herein defined as the value of peak height in the emission spec~rum curve) and amount of BaF2 added in firing Y2Si5-Ce- and Fig. 4 shows a relation between relative emission ~- intensity (defined as above) and amount of BaF2 added in firing-Y2Si2O7:Ce.
Among yttrium silicates as host (or ma~r~x) of phosphor, ;
` ~2SiO5 (namely, SiO2/Y203=1) and ~ and ~ phases of Y2Si207 (namely, SiO2/Y203=2) are known. The present invention applies particularly to Y2SiO5 and Y2Si207.
The s~oichiometric mol ratio of ~he component materials ;~ 2 2 3 2/Y203_1 for Y2SiO5 phosphor, and SiO /Y 0 =2 for Y2Si207 phosphor. However, in actual systhesis of ~he phos-; phor, ~tha ratio SiO2/Y203 should be l.0 - 1.2, more preferably 1.2 for Y2SiO5 phosphor, and 2.0 - 2.5, more preferably 20 2.2 - 2.5 for Y2Si207 phosphor. It ~as found through analysis by powder X-ray diffraction than an excessive amount o~ SiO2 makes the synthesls easier resulting in higher lumiDous-efficiency.
Certain preferred embodlments of the invention are illustrated by the attached dra~ings in which:
Fig. 1 sho~s spectrum distributions of emission of Y2SiO~:Ce phosphors at electron beam excitation, wherein curve "a" i~dicates the phosphor made by Example I and curve "b" indica~es the phosphor made by conventional method and materials, Fig. 2 shows a relation between relative luminosity and amount of BaF2 added in firing Y2SiO5:Ce, _ 4 ---F~g. 3 shows a relation between relative emission intensity (herein defined as the value of peak heigh~ in the - emission spectrum curve~ and amount of BaF2 ~dded in firing Y2SiO5:
Ce, and Fig. 4 shows a relation between relative emission inten-sity (defined as above) and amount of BaF2 added in firing Y2Si207:Ce.
The effect of amount of BaF2 added in firing , Y2SiO5:Ce phosphor is sho~n in Fig. 2 and Fig. 3, wherein addition of BaF2 in an amoun~ of 0~01 - 0.2 mol per 1 mol of the Y2SiO5:Ce .
phosphor causes the abovementioned improved effect, and the preferable range ls 0.03 - 0.1 mol per l-mol of the phosphor, and further, the highes~ luminosity and the highest peak value of ;~ emission intensi~y are attained in the optimum range of 0.05 -0.07 mol per 1 mol of the phosphor. For the abovementioned aptimum ;~ range of BaF2, the peak value of the luminosity of the present phosphor is 160% and ~hat of the emission intensity of the same is ;~; l10% ln~comparison~with those values of the conventional Y2SiO5:Ce p~osphor fired with YF3 addition.
20 ~ The effect of amou=t ~of BaF2 added in firi=g Y2Si2O7:Ce ph~osphor is~shown in Fig. 4, wherein addition of DaF2 in an amoune of 0.01 -~O.l mol per l mol of the Y25i2O7:Ce phosphor~ causes the abovementioned improved effect, aDd the preferable range is in an amount of 0.03 - 0.08 mol per l mol of the phosphor, and further, the highest peak value of emission inte=sity i8 attain~d at around the optimum amount of approxi=ately 0.05 mol per 1 mol of ~he phosphor.
For the abovementioned optimum amount of BaFzp the peak value of the emisslon intensity of the present phosphor is 150 to 160% in comparison with the value of ~he conventional Y2Si207:Ce ` 1~4: L2~3~
phosphor fired without BaF .
Analysis by powder X-ray diffraction does not clearly `~ show imperfection of la~tice constant which indicates production of barium silicate or intermixing of barium ions in the la~tice.
~` Many additives, for instance, fl~oride compounds, such as AlF3, MgF29 CaF2, SrF2, LiF, ZnF2, and also compounds of barium, such as BaC03, Ba(N03j2, BaC12, have been tested as mineralizer or flux in firing the Y2SiO5 and Y2Si207 phosphors. ~mong the above-me~tioned tested compounds, none ~as found to improve the lumino-sities or emissi~n intensities of the phosphors.
Prom the abo~ementioned facts, the principle of the improvement can be hypothetically elucidated as follows:
The improvement in Y2Si207:Ce phosphor is supposed to be caused by the effect of BaF2 as mineralizer. While the improvement in Y2S105:Ce is supposed to be caused by the increase of emission - i~tenslty at around 450 nm wavelength (as shown by curve "a" of Fig. 1) where specific visual sensitivity of the eye is high, this improvement is attained presumably not only by the function of BaF2 as ~ineralizer, but also by some intangible contribution of barium . 20~ to improvement of the emission. However, the importance is in that uch improvement is effected by addition of BaF2 only, and not by other substance.
In ~he firing of the Y2SiO5:Ce phosphor, firing at a temperature of 1200 - 1500 C in air or a slightly reducing atmos--:- :
~ phere for 3 hours gives a good result. The emissio~ intensity, - hereln defined as, the value of the peak height in the emission spectrum curvej is the highest when ~he firing is made at around .
~ 1300 C, but the firing temperature to give the peak of the emission `~:
` intensity is dependent on concentration of cerium. For instance, when 0.01 mol of Ce is added to l mol of phosphor, the peak is obtained by firing at around 1300 C.
~04~;288 Between the abovementioned two firlng conditions, the latter one, namely, firing at 1400C with the 0.03 mol Ce addition to 1 mol phosphor results in a lit~le higher luminosity, but in a lower peak value of emission intenslty.
An analysis by powder X-ray diffraction proved that a ~lring at over 1200C for 3 hours formed Y2SiO5 compound.
In the firing of the Y2Si207 phosphor, firing at a tem-perature of 1260 to 1430C in air or a slightly reducing atmosphere for 3 to 4 hours makes a good result. Since the transition tempera-ture from ~-Y2Si207 to a-Y2Si207 or to y-Y2Si207 compound is 1250 C
+ 10C or 1445C + 10C, respectively, the firing should be done a~ a temperature between 1260C and 1430 C.
In the below-mentioned examples, 99.~99~ pure Y203 9 99.999 pure YF3 and 99.9% pure CeO2 manufactured by Shinetsu Chemical Co., Ltd. of Japan, 99.999% pure SiO2 manufactured by Mathey ~ Co., Ltd. of England and ultrapure BaF2 manufactured by E. Merk AoG~
of German Federal Republic are used as the ~tarting material~.
In ~he measurement of the luminosity, ~he calibrations for relative luminosity curve are made by using a Xodak Wratten ~ (Trade Mark)~Mo. 106 fil~er and a photomultiplier of S-4 spectrum sensitivity.
Example I
In this Example a phosphor is made from:
Yttrium oxide ~Y203) ....................... 73.02 gr Anhydrous silicon oxide (SiO2) ............. 23~7S gr Cerium oxide ~CeO2) ....................... 3.44 gr Barium Fluoride ~BaF2) .................... 2.89 gF
The abovementioned starting materials are powdered and mixed well in a bowl, and ~hen the mixture is placed in a platinum boat and heated in air at 1300 C for 3 hours.
l~ Z8~3 An analysis by powder X-ray diffraction proved that the phosphor made in this manner consisted mainly of Y2SiO5:Ce. The spectrum distribution of this phosphor is shown in Fig. 1 by curve "a". The peak value of the spectrum curve of this phosphor is al- ;
most equal to known phosphor of Y2Si205:Ce that is fired with YF3 as mineralizer, and its luminosity is as high as 160~ of that of the abovementioned known phosphor.
Example II
~' The starting materials of Example I are powdered and mixed well in a bowl, and then the mixture is placed in an alumina boat , ~ .
~`~ and heated at 1400C for 3 hours in a slightly reducing atmosphere .~
of argon gas containing 5% hydrogen.
The phosphor made in this manner has a luminosity as high as 138% and the emission intensity at its peak as~high as 110%, co~pared with those of the abovementioned known Y2SiO5:Ce phosphor that is fired without BaF2.
Example III
In this Example a phosphor is made ~rom:
Yttrium oxite (Y203) ....l................... 223.58 gr Anhydrous silicon dioxide (SiO2) .,.......... 144.Zl gr Cerium oxide (CeO2~ ......................... 3.44 gr Barium Fluoride~SBaF2) .. ; 8.76 gr The abovementioned starting materials are powdered and mixed-well in a bowl. Then the mixture is placed in a platinu~
boat and heated in air at 1350C for 1 hour. The product is again po~dered and mixed in a bowl and heated at 1350C for 2 hours. An analysis by powder X-ray diffraction proved that the phosphor made in this manner consisted of Y2Si207:Ce. The peak value of ~; the spectrum curve of this phosphor is as high as 150 of that of 30 the conventional Y2Si207:Ce phosphor that: i~ fired without BaF2. `~
.
Example IV
The starting materials of the Example III are powdered and mixed well in a bowl, and then the mix~ure ls placed in a graphite boat and heated at 1350C for 3 hours in a slightly reducing atmosphere of argon gas containing 5% hydrogen. The phosphor made in this manner has an emission intensity at its peak as high 2S 150~ of that of the abovementioned known Y2Si207:Ce phosphor that ls fired wltho~t BaF2.
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Claims (7)
1. A phosphor which is the fired reaction product of a mixture of Y2O3, SiO2, CeO2, and BaF2, the mol ratio of SiO2 to Y2O3 in the mixture being represented by a formula of SiO2/Y2O3 = X where 1.0? X? 1.2 and the mol ratio of BaF2 to Y2O3 in the mixture being represented by a formula BaF2 / Y2O3 = Y where 0.01? Y? 0.2 for Y2SiO5 : Ce phosphor or the mol ratio of SiO2 to Y2O3 being represented by a formula SiO2 / Y2O3 = X' where 2.0? X'? 2.5 and the mol ratio of BaF2 to Y2O3 in the mixture being represented by the formula BaF2/Y2O3 = Y' where 0.01? Y'? 0.1 and whose crystallogical designation is .beta.-pyrosilicate for Y2Si2O7 : Ce phosphor.
2. A phosphor which is the fired reaction product of a mixture of Y2O3, SiO2, CeO2, and BaF2 the mol ratio of SiO2 to Y2O3 in the mixture being represented by a formula of SiO2 / Y2O3 = X where 1.0? X? 1.2 and the mol ratio of BaF2 to Y2O3 in the mixture being represented by a formula BaF2 / Y2O3 = Y where 0.01? Y? 0.2.
3. A phosphor which is the fired reaction product of a mixture of Y2O3, SiO2, CeO2, and BaF2, the mol ratio of SiO2 to Y2O3 being represented by a formula SiO2 / Y2O3 = X' where 2.0 ?X'? 2.5 and the mol ratio of BaF2 to Y2O3 in the mixture being represented by the formula BaF2 / Y2O3 = Y' where 0.01? Y'?0.1 and whose crystallogical designation is .beta.-pyrosilicate.
4. A method for preparing a phosphor by the steps of mixing together Y2O3, SiO2, CeO2 and BaF2 and firing the resultant mixture in air or a weak reducing atmosphere, characterized by (a) firing at a temperature in the range of 1200 - 1500°C a mixture in which the mol ratio of SiO2 to Y2O3 is represented by the formula SiO2 / Y2O3 = X where 1.0? X? 1.2 and the mol ratio of BaF2 to Y2O3 is represented by the formula BaF2 / Y2O3 = Y where 0.01? Y? 0.2 to produce Y2SiO5 : Ce phosphor or (b) firing at a temperature in the range of 1260°C - 1430°C a mixture in which the mol ratio of SiO2 to Y2O3 is represented by the formula SiO2 / Y2O3 = X' where 2.0? X'? 2.5 and the mol ratio of BaF2 to Y2O3 is re-presented by the formula BaF2 / Y2O3 = Y' where 0.01? Y'? 0.1 and whose crystallogical designation is .beta.-pyrosilicate to produce Y2Si2O7 : Ce phosphor.
5. A method of increasing the emission intensity of a Y2SiO5:Ce phosphor at around the 458nm wavelength comprising adding BaF2 to a mixture of Y2O3, SiO2 and CeO2, wherein the BaF2 is added in an amount such that the BaF2/Y2O3 mol ratio is 0.01 to 0.2 inclusive and wherein the SiO2/Y2O3 mol ratio is 1.0 to 1.2 inclusive, and thereafter firing the BaF2-containing mixture at a tem-perature of the order of 1200-1500°C in air or in an inert gas containing up to 5% hydrogen to produce a cerium-activated phosphate phosphor exhibiting increased luminosity and relative emission intensity.
6. The method of claim 5 wherein the amount of BaF2 added to the mixture is such that the ratio of BaF2/Y2O3 is 0.03 to 0.1.
7. The method of claim 5 wherein the amount of BaF2 added to the mixture is such that the ratio of BaF2/Y2O3 is 0.05 to 0.07.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP48024951A JPS5750833B2 (en) | 1973-03-02 | 1973-03-02 | |
| JP9682273A JPS554796B2 (en) | 1973-08-28 | 1973-08-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1041288A true CA1041288A (en) | 1978-10-31 |
Family
ID=26362545
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA193,868A Expired CA1041288A (en) | 1973-03-02 | 1974-03-01 | Cerium-activated yttrium silicate phosphor |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1041288A (en) |
| DE (1) | DE2409953C3 (en) |
| GB (1) | GB1452180A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4141855A (en) * | 1975-06-02 | 1979-02-27 | Matsushita Electric Industrial Co., Ltd. | Method of producing cerium-activated phosphor of improved characteristic |
| JPS5918433B2 (en) * | 1975-06-02 | 1984-04-27 | 松下電器産業株式会社 | fluorescent material |
| EP0253589A1 (en) * | 1986-07-14 | 1988-01-20 | AT&T Corp. | Display devices utilizing crystalline and powder phosphors |
| KR100450792B1 (en) | 1999-12-23 | 2004-10-01 | 삼성에스디아이 주식회사 | Phosphors based on yttrium silicate for driving at a low voltage |
| JP4228628B2 (en) * | 2002-08-29 | 2009-02-25 | 住友化学株式会社 | Phosphor for vacuum ultraviolet light-emitting device |
-
1974
- 1974-02-28 GB GB918874A patent/GB1452180A/en not_active Expired
- 1974-03-01 DE DE2409953A patent/DE2409953C3/en not_active Expired
- 1974-03-01 CA CA193,868A patent/CA1041288A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2409953C3 (en) | 1980-07-17 |
| DE2409953B2 (en) | 1979-11-15 |
| DE2409953A1 (en) | 1974-09-19 |
| GB1452180A (en) | 1976-10-13 |
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