JPH0245589A - Compound oxide fluorescent substance of rare earth element tantalum base activate with terbium - Google Patents

Abstract

PURPOSE:To obtain a fluorescent substance showing green luminescence with high luminance especially under X-ray excitation comprising a complex oxide fluorescent substance of rare earth element tantalum base activated with Tb having a specific composition. CONSTITUTION:The aimed fluorescent substance which is shown by the composition formula (Ln is Y, La, Gd or Lu; m, n and x are 0.95<=m<=1.05, 0<=n<=5.0, 5X10<-4=x<=0.1) and has <=50ppm Nb content. An especially preferable fluorescent substance among the fluorescent substance is a fluorescent substance wherein m, n and x are 0.98<=m<=1.02, 0.1<=n<=2.0 and 2X10<-3=x<=5X10<-2>, respectively and Ln is Gd. The fluorescent substance is produced by packing a raw material mixture of fluorescent substance into a heat-resistant container such as alumina crucible and burning at 900-1,500 deg.C (preferably 1,000-1,300 deg.C) usually for 1-72 hours. The burning may be carried out twice or more times and in this case, preferably the raw material mixture is initially preburnt at 1,000-1,200 deg.C and then burnt at 1,100-1,300 deg.C on and after second times.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a phosphor, and in particular to an improvement of a terbium (Tb)-activated rare earth tantalum-based composite oxide phosphor that emits high-intensity green light under X-ray excitation. I'm in trouble.

[Conventional technology]

Rare earth tantalate is used as a base material, and this is niobium (Nb).
A phosphor activated with thulium (Tm) emits high-intensity blue light upon X-ray excitation, and a phosphor activated with rare earth tantalate 'i7 Tb emits Tb under X-ray excitation.
It is known that it exhibits a characteristic green luminescence (Jo
Urnal of Luminescence Magazine, No. 3
Volume, page 109 (1970), Special Publication 1986-2206
Publication No. 3, JP-A-62-58244, JP-A-62
See Publication No.-246988, etc.

By the way, the Nb-activated rare earth tantalate phosphor has already been put to practical use as a blue-emitting intensifying screen used in combination with a regular type X-ray film. However, an intensifying screen using a Tb-activated rare earth tantalate phosphor in the phosphor layer has good photographic image quality when used in combination with orthotype X-ray film for X-ray photography. However, it has not yet been put into practical use because it has the drawback of low sensitivity (light conversion efficiency), and therefore, it is necessary to improve the luminance of Tb-activated rare earth tantalate phosphors under X-ray excitation. Various attempts have been made. The present applicant has also previously proposed a green-emitting phosphor with the composition formula (Lnl-xTbX)2o3・mTa205・WB2 that has higher brightness than the Tb-activated rare earth tantalate phosphor.
03 (However, Ln is Y, La, Gd and L
is at least one element selected from u, and X1m and W are 5X10'≦X≦0.1, 0.9, respectively
Using a composite oxide of rare earth tantalate and boron oxide (B20. We proposed a phosphor activated with Tb (patent application 1986).
-176010), but it is desired to develop a Tb-activated rare earth tantalate phosphor with even higher brightness.

[Problem to be solved by the invention]

The present inventors have developed a Tb-activated rare earth tantalate phosphor with the aim of providing a phosphor that emits green light with higher brightness especially under X1m excitation than conventional Tb-activated rare earth tantalate phosphors. As a result of extensive investigation into the relationship between the type and amount of elements that are inevitably added as additives or impurities to the salt phosphor and the luminance of the resulting phosphor under X-ray excitation, Tb activation was found. The rare earth tantalate phosphor and the compositional formula previously proposed by the applicant are (Ln, -E, Tb, x
)2o, ・mTa2o5・WB203 (However, Ln,
x, m and W are the same as above)
Activated complex oxide phosphor (these Tb-activated rare earth tantalate phosphors and Tb-activated complex oxide phosphors are collectively referred to as
In this specification, FTb-activated rare earth tantalum-based composite oxide phosphor] contains niobium (Nb) and/or manganese (Mn), which are accompanying impurity elements.
It has been found that the correlation between the content of phosphor and the luminance of the phosphor is particularly remarkable. Nb and Mn are Ta raw material ore (
Since Nb is a component element of Nb (Nb is a component element of Nb), Nb is usually a component element of 1.5% of Nb in commercially available Ta compounds used as raw materials for rare earth tantalum complex oxide phosphors.
O o ppm or more, Mn is contained in several tens of ppm or more, but by refining such a commercially available Ta compound and using a Ta compound with a lower Nb and/or Mn content, it is possible to activate Tb. The inventors have discovered that the luminance of rare earth tantalum complex oxide phosphors can be significantly improved compared to conventional ones, leading to the present invention.

[Means to solve the problem]

The Tb-activated rare earth tantalum complex oxide phosphor of the present invention has a composition formula (Lnl-X, TbX)203·mTa2o-nB2o
3 (However, Ln is at least one element selected from Y, La, Gd, and Lu, and m, n, and X are 0.95≦m≦1.05, 0≦n≦5, respectively.
．． 0 and 5X10'≦X≦0.1. ), and the Nb content is 50 ppm or less.

Further, the Tb-activated rare earth tantalum complex oxide phosphor of the present invention has a composition formula (Ln 1+X, TbX) 203-mTa205
"nB203 (However, at least one element selected from Lnl-iY, La, Gd and Lu, m
, n and X are each 0.95≦m≦1.05 r
The number satisfies the following conditions: O≦n≦5.0 and 5X10'≦X≦01. ) and is characterized by having a Mn content of 10 ppm or less.

The present invention will be explained in more detail below.

The Tb-activated rare earth tantalum complex oxide phosphor of the present invention can be produced by the method described below.

First, as phosphor raw materials, the following four types of raw materials, which have been sufficiently purified and have a total amount of Nb of 50 ppm or less or a total amount of Mn of 10 ppm or less, are used: 1) Yttrium oxide (Y2O2), lanthanum oxide (L
a203), gadolinium oxide (Gd20x), lutetium oxide (Lu203), and K that is easily heated
y2o3゜La2O31Gd2O3+ One or more compounds selected from yttrium compounds, lanthanum compounds, gadolinium compounds, and lutetium compounds, such as nitrates, carbonates, chlorides, hydroxides, and oxalates, which can be converted into Lu2O3.

it) tantalum oxide (Ta205) and tantalum dioxide (Ta02) which can be converted to Ta205 by heating
, one or more compounds selected from tantalum compounds such as tantalum chloride (TaC15), 111) boron oxide (B203) and B2O by heating.
IV) One or more compounds selected from boron compounds such as boric acid (H3BO3) which can be converted to Tb2O3 by heating; salt,
Terbium compounds such as oxalate, one of the compounds selected from
A species or two or more species are used. The above four types of phosphor raw materials are stoichiometrically (Lnl-X, TbX)203@mTa205/nB2
03 (however, Ln 1 m I n ,! + has the same definition as above), and mix thoroughly. Mixing can be done using ball mills, mixer mills,
It may be carried out dry using a mortar or the like, or it may be carried out wet in the form of a paste using water, alcohol, or the like as a medium. From the viewpoint of the emission intensity of the obtained phosphor, m, n and X
The values of 0.98≦m≦1.02, o, i≦n≦, respectively.
2.0 and 2X10-3≦X≦5X10-2, and when Ln is Gd, a particularly high-luminance phosphor can be obtained.

Note that among the Tb-activated rare earth tantalum complex oxide phosphors of the present invention, phosphors that do not contain B2O3 (in the above composition formula,
Needless to say, when producing a fluorescent material (in the case where n = O), the above-mentioned phosphor raw material 111] is not used.

Next, the phosphor raw material mixture is filled into a heat-resistant container such as an alumina crucible or a quartz crucible, and fired. Firing is carried out at a temperature of 900 to 1500°C, but 1000 to 13°C.
It is more preferable to carry out the reaction at a temperature of 00°C.

In addition, firing may be performed twice or more, in which case first pre-calcining at 1000 to 1200°C,
It is more preferable to perform the second and subsequent firings at 1100 to 1300°C. The firing time varies depending on the filling amount of the phosphor raw material and the firing temperature, but generally it is 1 hour to 72 hours.
It is appropriate to do it on time. That is, in general, the higher the firing temperature, the shorter the firing time; for example, when the firing temperature is 120
At 0°C, 15 hours of firing is required to obtain the rare earth tantalum complex oxide phosphor of the present invention that exhibits a predetermined luminescence intensity, but when fired at 1400°C, it only takes 4 hours. .

Incidentally, in producing the rare earth tantalum complex oxide phosphor of the present invention, the method for producing a rare earth mental acid salt phosphor disclosed in, for example, Japanese Patent Publication No. 58-22063,
Li25o4. LICI.

A compound such as BaC1□ may be mixed as a flux.

After the firing is completed, the desired composite oxide phosphor of the present invention can be obtained by subjecting the resulting fired product to various processing operations commonly employed in the production of phosphors, such as pulverization, washing, drying, and sieving. .

In this way, a composition having a Nb content of 50 ppm or less or a Mn content of 10 ppm or less is obtained.
A Tb-activated rare earth tantalum complex oxide phosphor represented by B2O3 is obtained.

〔Example〕

Next, the present invention will be explained by examples.

Example 1 Commercially available tantalum pentoxide (Ta205) containing 370 ppm Nb and 180 ppm Mn was purified to
Ta205 having a b content of 1 ppm or less was obtained.

Next, yr linium oxide (Gd203) 44
．． 6! ',.

The above Ta205 with Nb content of 1 ppm or less 54.
9 P and terbium oxide (Tb407)
Each phosphor raw material of 0.465 P was thoroughly mixed, and LICl and L1□SO4/H2O were mixed as fluxes at 501 fk% each of the above phosphor raw materials, packed in an alumina crucible, placed in an electric furnace, and heated in air. It was baked at a temperature of 1250° C. for 7.5 hours. After firing, wash the fired product with water,
After drying, it was sieved and the composition formula was (GdO,99
'Tbo,. 1) A phosphor [I] represented by 205.Ta205 was manufactured.

Next, instead of the T & 20s purified above with an Nb content of 1 ppm or less, Nb2O5 was added to it, and the Nb content was 20 ppm or less, respectively.
Phosphors [■],
Phosphor [111] and phosphor [■] were manufactured.

Separately, for comparison, instead of the above purified Ta20s with a Nb content of 1 ppm or less, 370 ppm of Nb (same amount as the Nb contained in Ta205 before purification) was added. ) Added Ta205 and N
Commercially available Ta205 with b content of 1,270 ppm
The phosphor (R1) was prepared in the same manner as the phosphor [l] except that
) and phosphor CRII,] were manufactured.

The phosphors [I] to [■] obtained by further K and the phosphors [R[) and the Nb particles contained in CRIME (each phosphor was dissolved in hydrofluoric acid, and by ICP analysis)
When each of these phosphors was irradiated with X-rays of 80 kVp and the luminance was measured, the results shown in Table 1 were obtained.

Table 1 Figure 1 shows (GdO,991TbO,0+)205 ・
Nb content in Ta205 phosphor and 80 kV
This is a graph showing the relationship between luminescence brightness when excited by X-rays of p. It is shown.

As shown in Figure 1 (GdO, 99, TbO, 01
)203'' The luminance of the phosphor represented by Ta2o5 improves as the amount of Nb contained in the phosphor decreases, and particularly when the content of Nb is about 50 ppm or less, the luminance increases markedly.

Although not illustrated, the compositional formula is (Lnl-,.

Tbx)203·mT a 20 s·nB2O, (Gd0.99.

Tbo,. 1) It was confirmed that there is almost the same correlation between the Nb content in the phosphor and the emission brightness for Tb-activated rare earth tantalum complex oxide phosphors other than the 203/Ta205 phosphor as shown in Figure 1. It was done.

Example 2 Commercially available tantalum pentoxide ('ra2o5) containing 180 ppm Mn and 370 ppm Nb was purified to obtain Ta205 with a Mn content of less than i ppm. Next, gadolinium oxide (Gd203) 4
4.6 The above T&20 with a PMn content of 1 ppm or less
5 54-9 F boron oxide (B203)
0.870 f and terbium oxide (Tb40
7) Thoroughly mix each phosphor raw material of 0.465 P, and further add LiC1 and L12 as a flux.
50 each of the above phosphor raw materials for SO4 and R20! i% mixed aluminum nuts? and put it in an electric furnace for 12 hours in the air.
It was baked at a temperature of 50° C. for 15 hours. After firing, the resulting fired product was washed with water, dried, and then sieved to give the composition formula (G
da,qq'Tbo,. 1) 203・Ta205・0
．． 1 B20. A Tb-activated rare earth tantalum complex oxide phosphor [■] represented by the following formula was produced.

Next, the Ta is purified and the Mn content is 1 ppm or less.
MnC1° was added to this instead of O, and the Mn content was 2 pl)m, 20 ppm, and 75 ppm, respectively.
The above phosphor [V
, ), phosphor [■], phosphor [■] and phosphor [■] were produced.

Separately, for comparison, instead of the purified Ta205 with Mn of 1 ppm or less, 180 ppm of Mn was added to this.
A phosphor CR11l] was produced in the same manner as the phosphor (V) except that T&20s to which OMn (the same amount as Mn contained in Ta205 before fJW) was added was used.

The amount of Mn contained in the phosphors [■] to [■] thus obtained and the phosphors (RI [IE) (each phosphor was dissolved in hydrofluoric acid and analyzed by ICP). When each of these phosphors was irradiated with X-rays of 80 kVp and the luminance was measured, the results shown in Table 2 were obtained.

Table 2 Figure 2 shows (GdO,99”bo,01)203・Ta
205・0.1 This is a graph showing the relationship between the Mn content in the B2O3 phosphor and the relative emission brightness when excited with 80 kVp X-rays. It is expressed as a relative value when the luminance of the phosphor, which is ppm or less, is set to 100.

As shown in Figure 2 (GdO, 99, TbO, Ol
)203・Ta205・0.1B203 The luminance of the phosphor increases as the amount of Mn contained in the phosphor decreases, and especially when the amount of Mn is approximately 10 p
When the temperature was below pm, the luminance was significantly increased.

Although not illustrated, the compositional formula is (Lnlx +Tb
X) 203・mTa2o5・nB2O3,
(Gd0.99'TbO,Oj)203・Ta,,
O,,・0.1 B20. Regarding Tb-activated rare earth tantalum complex oxide phosphors other than phosphors, M in the phosphor
It was confirmed that there is a correlation between the n content and the luminance almost similar to that shown in FIG. 2.

The intensifying screen using the terbium-activated rare earth mental complex oxide phosphor of the present invention as a fluorescent film has particularly excellent graininess, and can be used in addition to general X-ray photography using X-rays with a tube voltage of 50 to 150 kV. It can be used in combination with a single-sided emulsion film or a double-sided emulsion film for low-pressure X-ray photography (mammography, etc.) using X-rays with a tube voltage of 20 to 40 kV.

〔Effect of the invention〕

As detailed above, by removing as much as possible the amount of Nb and/or Mn contained in the Tb-activated rare earth tantalum complex oxide phosphor, the green emission intensity especially under X-ray excitation can be improved to that of the conventional one. It can be significantly improved compared to
For example, it is useful for intensifying screens and X-ray fluorescent screens used in combination with orthotype X-ray films.

[Brief explanation of the drawing]

FIGS. 1 and 2 each show a T containing the phosphor of the present invention.
Nb in b-activated rare earth/tal complex oxide phosphor
It is a graph showing the correlation between the content and the relative luminance and the correlation between the Mnn-containing color and the relative luminance.

Claims (2)

[Claims] (1) The composition formula is (Ln_1_-_x, Tb_x)_2O_3・mTa_
2O_5・nB_2O_3 (However, Ln is Y, La, G
At least one element selected from d and Lu, and m and no x are respectively 0.95≦m≦1.05, 0≦n≦5.0 and 5×10^-^
This is a number that satisfies the condition 4≦x≦0.1. ) and characterized in that the content of niobium (Nb) is 50 ppm or less. (2) The composition formula is (Ln_1_-_x, Tb_x)_2O_3・mTa_
2O_5・nB_2O_3 (However, Ln is Y, La, G
At least one element selected from d and Lu, m, n and x are respectively 0.95≦m≦1.05, 0≦n≦5.0 and 5×10^-^
This is a number that satisfies the condition 4≦x≦0.1. ), and has a manganese (Mn) content of 10 ppm or less.