Fluorescence response of barite to gamma radiation

Radiar. fhys. Chem. Vol. 46, No. 3, pp.321-327, 1995 Pergamon

Elsevier Science Ltd. Printed in Great Britain

0969406x5(94)0012&6

FLUORESCENCE

RESPONSE OF BARITE TO GAMMA RADIATION

S. K. YOUSSEF,’ L. A. GUIRGUIS* and N. A. SHAHIN3 ’Radiation Protection Department, NRC, Atomic Energy Authority, Cairo, *Nuclear Material Corporation, Cairo and ‘Physics Department, University College for Girls, Cairo, Egypt (Accepted IS September 1994) Abstract-Detailed studies on the characteristic behaviour of gamma radiation induced luminescente emission for different natura1 barite samples collected from the Egyptian deserts, noted as “black”, “yellowish” and “colourless” barites; and laboratory prepared synthetic ones of equivalent compositions have been given. The results showed an equivalent luminescente characteristic behaviour for both natura1 and synthetic ones. The optimum condition of the excitation energy necessary to induce the luminescente emission of the colour center depends on the type of the dopant activators in the basic matrix of barite (BaSO,). The intensity of the excitation energy varies linearly with the samples gamma absorbed dose over the range 10°-104Gy. The sensitivity of the gamma radiation induced luminescente presents a linear relation with the samples gamma absorbed dose over the range 10°-IO’Gy for both natura1 “n” and synthetic “s” barites. More detailed studies concerning the relation between the excitation and radiophotoluminescence “luminescente emission” of barite with the configuration farms of the electronic charge (+ve and -ve ions) imperfections induced by the effect of the doped activators in the BaSO, network are discussed.

EXPERIMENTAL PROCEDURE

INTRODUCTION Thermoluminescence

response

of solid state material

such as: LiF:Dy, natura1 sand, geological material, barite, are reported respectively by many authors (Atkin, 1974; Gomaa and Eid, 1976; Gomaa and Morsi, 1976; Gomaa and Eid, 1977; Mejdahl, 1968; Youssef et al., 1987a; Youssef et al., 1987b; Youssef et al., 1993). Moreover, information about radiophotoluminescence of natura1 material, especially barite, is stil1 very limited. Meanwhile, radiophotoluminescence of glass matrix containing borosilicate or phosphate and both of their metallic compositions, and/or polymerie materials has been considered in detail (Adawi et al., 1987; Salama et al., 1988; Youssef et af., 1988). As barite is a natura1 material containing a wide variety of activator elements as dopants, it was necessary to carry out kinetic studies on radiophotoluminescence mechanisms using some varieties of natura1 barites and laboratory prepared synthetic ones of equivalent composition. The aim of the present work is to identify the dopant activator elements in the basic matrix of barite (BaSO,) which show the main effective response of the colour centers for developing an effective synthetic laboratory preparation radiophotoluminescente barite detector of wide utilization range in the different radiation sciences.

1. Sample collection

Natura1 barite samples were collected from different places in the Egyptian deserts. They were nominated according to their composition as “colourless”, “yellowish” and “black”. 2. Barite chemistry Chemical analyses thoroughiy washing with distilled water samples were then Table

of barite were carried out after the different natura1 samples for dust removal. The cleaned dried at 105°C. The analysis

1.Chemical compositions of the different studied natura1 barite types Weight (%)

Component Si0 I A&O, Pe,O, TiO, Mn0 Ca0 QO Sr0 Ba0 SO, OH+

Yellowish barite 0.40

0.35 I .39 0.05 0.09 UDL UDL 0.10 60.40 34.10

1.65

UDL: Undetectable limit 321

Colourless

barite 0.30 UDL

I .04 0.09 0.24 2.80 0.94 UDL 57.60 32.50 4.53

Black barite 0.29 0.42 8.19 2.30 0.10 5.54 UDL UDL 50.50 28.52 3.70

S. K. Youssef et

322

al.

Table 2. The studied synthetic dopant mixing with synthetic BaSO, Synthetic barite type

Dopant type and concentration ‘+ Fe,O, BaSO, + 0.10% *+Sr0 + 1.39% ‘+ Fe,O,

Black Colourless Yellowish

Table 3. Excitation and emission behaviour characterizing the different natura1 (n) and synthetic (s) barite types Excitation band

Barite type Colourless

Sample condition ”

242,t 215 242.f 215 230. 270$ 235, 2701 250 254

S

n

Black

S

n

Yellowish

Unirradiated Acxc (nm)

S

Irradiatedt I EIC (nm) 242,f 215 242,$ 215 233, 2701 233, 270% 256 256

Emission band Unirradiated 1em (nm) 395,f 455 398,X 439 435, 495f 421, 4911 335, 390% 332, 395%

Irradiatedt I (ncJ) 391,$ 452 394,f 454 436, 494t 430, 4941: 334, 388% 330, 393%

tSamples annealed at 500°C for one hour before irradiation to 1.5 Gy gamma absorbed dose. $Main emission of excitation band.

technique was mainly based on conventional spectrophotometric and/or gravimetrie techniques. The results of chemical analyses for the three different varieties are noted in Table 1.

Yellowish

From Table 1 black barite showed more doped activator of Fe,O,, Ca0 and TiO, in its main basic composition Ba0 of respective relative percentage weight ratios (RWT) 8.20, 11.00 and 4.60. Meanwhile, the main basic composition of colourless barite is doped with more MgO, Mn0 in addition to Fe,O, of respective RWT 1.60, 0.42 and 0.50. Also, the yellowish one contained more dopant activator of Sr0 in addition to Fe,O, and Al,OJ of respective RWT 0.10, 1.39 and 0.60. Analysis of the noted data in Table 1 showed that the percentage weight of the main basic composition, BaO/SO, and/or BaO/ (Ba0 + SO,) in the three different barite compositions is mostly unique, i.e. respectively about 64% and 1.77%. Table 2 showed the synthetic activator selection in the synthetic BaSO, according to a previous study (Youssef et al., 1988) on thermoluminescence (TL) mechanisms in natura1 barite as wel1 as the noted analytical chemical analysis of natura1 barite samples in Table 1. 3. Experimental measurements

275 Wavelength

325 (nm)

Fig. 1. Excitation spectra of unirradiated barite: (-.-.-) natura1 barite and (---) synthetic barite.

Measurements of the induced radiophotoluminescence through the effects of gamma radiation on natura1 Egyptian barite samples and on laboratory prepared synthetic ones (Table 3) were performed using Shimadzu Spectrophotometer RF-540. Both barite species were laboratory prepared in disc forms of 12 mm diameter and 1.0 mm thick and of 25 mg sample weight. For each barite type, the optimum excitation wavelength band was experimentally optimized before the performance of luminescente measurement. Also, the synthetic barite was prepared by coprecipitation of the different synthetic dopant activators as noted in Table 1 with BaSO, (by the addition of dilute sulfuric acid to the barium chloride). The different prepared samples were treated thermally hefore gamma irradiation hetween temperature and 700°C for one hour in

room 100°C

Fluorescente response of barite to gamma radiation Yellowish

!

NBS 25°C (room

16

300

323

Black temperature)

500

400

400

300

500

Wavelength

300

400

Fig. 2. Luminescente emission spectra of barites in different annealing conditions irradiation: (-.-.-) natura1 barite and (---) synthetic barite. intervals. The annealed samples were irradiated to different gamma absorbed doses over the range 10°-105 G; from an 6oCo gamma cell.

Colourless

.

A 275

nm . 230 nm

Black

x 275 nm 0 242 nm

Yellowish

?? 250

nm

l 0

1000

500

Annealing temperature

(“C)

Fig. 3. Varition of the samples annealing temperature with the UV-excitation light.

500

600

(nm)

RESULTS AND

bcfore gamma

DISCUSSION

Figure 1 illustrates the excitation spectra of the non-irradiated natura1 and synthetic crystals of barite samples at annealing temperature of 500°C for one hour. In Fig. 2, the induced luminescente spectra are detected for samples in different annealing temperature conditions between room temperature (about 25°C) and 700°C for one hour. The data of Figs 1 and 2 showed that: (1) the intensity and wavelength of the UV-excitation energy necessary to induce the visible quanta of the luminescente emission, which featured the colour centers of the different barite types, is found to be a factor depending on the barite type, and (2) the luminescente emission intensity (RPL) showed an increased response upon increasing the annealing temperature to 500°C for one hour, beyond which decreases. This latter effect may be ascribed to the thermally stimulated damage encountered the induced colour center and their traps in the barite crystals. The same behaviour is also noted when the barite crystals are excited by UV light. Figure 3 shows the effect of annealing temperature on the excitation of barite samples by UV light. The data showed an increased excitation sensitivity up to 500°C annealing temperature for one hour beyond which the response decreased. Table 3 finalized the main feature of the excitation and emission bands found to be with samples annealed at 500°C for one hour. The predicted results in Table 3 from Figs 1, 2, 4 and 5, showed that the excitation and luminescente

S.

324

K. Youssef et al. that the excitation energy (E,,) is the relative ratio between the intensity of the induced luminescente, 1‘, and UV-excitation light intensity, luv, for samples irradiated to different gamma absorbed doses. Assuming that the coefficient of excitation energy, (E,, Loer>is defined as the slope of the noted relations in Fig. 6. Table 4 depicts that data of (Eexc)coefand defined as E,,,/l Gy y -dose induced changes of E,,, due to 1 Gy y-dose for the three different barite types. According to Table 4, in the case of yellowish barite, (L )coefwas found to be 3.545 times greater than that of colourless barite. Furthermore, the noted deviation between (E,,,),,,f for synthetic and (Eexc)cWr for natura1 barite is ranged over f lO-20%. This may be attributed to the changing of the ambient laboratory conditions from that already presented in the nature of the Egyptian deserts. Figures 7 and 8 present the linear relation of the luminescente response with the samples gamma absorbed dose over the range 10°-10’ Gy for natura1 and synthetic barites. The luminescente coefficient, (EcmLrr of the linear relations is defined as the induced luminescente intensity by 1 Gy gamma absorbed dose, is also noted in Table 4. According to the above findings, it may be possible to nominate the following:

Yellowish

80

Black

60

275 Wavelength

325 (nm)

Fig. 4. Excitation spectra of barites after irradiation to 1.5 x 102Gy gamma doses: (-.-.-) natura1 barite and (---) synthetic barite.

(i) The natura1 collected barite and equivalent ones of the laboratory synthetic preparation showed approximately equivalent excitation and luminescente characters for both non-irradiated and irradiated samples. (ii) Upon gamma irradiation of the samples, the behaviour of the excitation as wel1 as the induced luminescente emission characterizing these created colour centers in the barite crystals depicted the following:

fa>The

excitation energy E,, per 1 Gy required to induce a luminescente response per 1 Gy of yellowish barite is found to be 3.5-4.5 times higher than that of the colourless type and about 2.5 times higher than that of the black barite. (b) the induced luminescente response per 1 GY Een, is relatively high in case of colourless type followed by black and yellowish types, and

emission bands position is not affected by gamma irradiation. Meanwhile, the emission intensity as wel1 as that correspondence of the induced luminescente response increases with increasing of the samples gamma doses. Figure 6 presents a linear response of the excitation energy with the samples gamma absorbed dose over the range 10°-104Gy. Assuming

Table 4. Excitation and luminescente emission sensitivity per 1 Gy for the different barites Emission Excitation Barite type

Colourless Black

Sample condition n s n S

Yellowish

n S

A = Wc.e)~~r and B = W,),,,;

B A

AJA,

AJA,

0.00025 0.00027 0.00043 0.00038 0.00113 0.00094

1.00

1.00

1.oo

1.08

1.72 1.41 4.57 3.48

0.88 0.83

B, /B,

BJB,

t

$

t

t

0.019 0.021 0.0012 0.0014 0.00074 0.00066

0.025 0.027 0.012 0.014 0.00073 0.00069

1.00 1.oo 0.063 0.067 0.039 0.035

I .oo 1.00 0.048 0.052 0.029 0.026

t

1

1.10

1.10

1.20

1.20

0.89

0.94

i refers to different barite types and c to colourless; s refers to synthetic and n to natura1 barites; t and f refers to first and second luminescente bands, respectively.

Fluorescente

Yellowish

325

Black

1.1 x 10’ Gy

‘-C.L

\.‘, “-<+

I 300

response of barite to gamma radiation

400

’

-7;

500

300

400

’’300

500

Wavelength

400

500

600

(nm)

Fig. 5. Luminescente spectra of barites irradiated by different gamma doses for samples annealed at 500°C: (-.-.-) natura1 barite and (---) synthetic barite.

(4 the

excitation and emission bands position is shifted from one barite type to another.

tion distribution of the electronic charge in the crystal. Addition of the dopant activators of:

These changed characters may be ascribed to the nature of the doped activators in the basic matrix composition of barite, BaSO,, as wel1 as the imperfec-

5.0% (a) in case of black barite, 8.3% 4tFe,0,, 2+Ca0 and 2.5% )+Ti203, (b) in case of yellowish barite, 1.39% 4+ Fe,O, and 0.1% 2+Sr0, and

Yellowish Black

Natura1 0

Synthetic .

A

0

.

x

Colourless

10-1I 100

I

I

lll,,,i

Fig. 6. Excitation energy (&J

I

10’

,

I,,,,,l

I

102

,

,

,

,

,

(

(

103

I

,

1,111,

104

Gamma absorbed dose (Gy) as a function of gamma dose for barite samples annealed at 500°C.

S. K. Youssef el al.

326 . 350 om band 0 405 nm band

Yellowish

A 490 nm band

Black Colourless

x 390 nm band

A 440 nm band

10’1 100

I

I

I111111

ti

II1,111

I

I

10'

I

I,,,,,

I

102

I

I,,,,,

,

103

104

Gamma absorbed dose (Gy) Fig. 7. RPL response as a function of “Co gamma absorbed dose for natura1 barites.

(c) in case of colourless barite, 1.05% 4+ Fe,O,, 0.94% 2t Mg0 and 0.24% 2t MnO, in mixed farms with BaSO, are acting as charge trapping centers (i.e. responsible for the colour centers) by virtue of its excess positive charge. The complex it forms is through sites where radiation induced changes can take place more easily. The concentration and nature of electrons and holes in these complexes are thus profoundly effected by the dopant activator types. Moreover, the configuration form of the complexes in case of black and colourless barites is too complicated so as the cloud density of the colour center is expected to be of increased probability. In the same flow and according to the present predicted results, with the increasing probability of the colour centers, the necessary UV-excitation light intensity of the induced luminescente decreases. Also, the induced luminescente of the

103

?? 350

A 405 ?? 500 X 390 o 440

T ? 0 A .z :

nm nm nm nm nm

band band band band band

emitted light quanta showed increased sensitivity. For these reasons, the necessary intensity of UV-excitation light to induce luminescente emission changes per 1 Gy gamma dose is relatively higher in the case of yellowish barite, of simpler complex forms than that of black and colourless barites, of too complicated complex forms. Meanwhile, the sensitivity of the luminescente response per 1 Gy of black and colourless barite is relatively higher than that of yellowish barite.

CONCLUSION

Gamma radiation induced effects on the colour center of barite crystals is beneficially utilized in the purpose of dosimetry using the radiophotoluminescence measuring technique. The excitation and the induced luminescente character exhibited a

Yellowish Black Colourless

i

10’1 100

I

I1l11111

I

10’

I

II,,,,

I

,

,

,

102

,

,

, ,

103

I

,

,

,,/,,

I

104

Gamma absorbed dose (Gy) Fig. 8. RPL response as a function of @‘Co gamma absorbed dose for synthetic barites.

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changeable behaviour from one barite type to another. Chemical analyses of the different natura1 barite types showed that the relative weight of Ba0 to Ba0 + SOr and Ba0 to SO, presented a unique ratio in the three different types. Furthermore, the existed activators in the main basic matrix varied from one barite type to another. According to the experimental intercomparison between natura1 and synthetic barite luminescente data, the center of luminescente in barite crystals may be ascribed to the created complexes from the imperfection distribution due to the charge carriers related to BaSO, with the noted activators in Table 2. Furthermore, the optimum excitation energy and its wavelength position as wel1 as the luminescente intensity and its wavelength position are influenced by the impurity ions. Also, the experimental results showed that: (1) radiation induced effects on the luminescente barites owned unique character for both natura1 and synthetic samples, (2) annealed samples at 500°C for one hour presented 4-12% decay in the initial gamma radiation induced signals during a period of 34 weeks as shown in Table 5, and (3) an extended gamma dose luminescente responses over 10°-105Gy gamma absorbed dose range.

REFERENCES Adawi M. A., Youssef S. K., Hashad A. M. and Badawy Z. M. (1987) High leve1 dosimetry by radiophotoluminescence of uranium doped borosilicate glass. Proc. Firsr Egypfian-British ConJ on Biophysics, Cairo University, Egypt, October 1987, pp. 217-225. Atkin J. M. (1974) Physics und Archeology, Oxford University, Oxford. Gomaa M. A. and Eid A. M. (1976) TL dosimetry using natura1 materials. Atomkernenergie 27, 274. Gomaa M. A. and Morsi M. M. (1976) TL dosimetry used fused silica. Atomkernenergie 28, 135. Gomaa M. A. and Eid A. M. (1977) TL application of heated sand. Atomkernenergie 29, 290. Mejdahl V. (1968) TL of Geologieal Materials, p. 453. Academie Press, N.Y. Salama A. A., Youssef S. K., Osiris W. G. and Hashad A. M. (1988) Effect of neutrons on some physical properties of cellulose nitrate for application in radiation dosimetry. Polym. Degradation Stability 22, 275. Youssef S. K., Henaish B. A. and Adawi M. A. (1987a) Induced effect of thermal anneahng on TL of natura1 sand and its application in gamma ray dosimetry. Proc. First Egypfian-British Con& on Biophysics, Cairo University, Egypt, October 1987, pp. 275-284. Youssef S. K., Henaish B. A. and Adawi M. A. (1987b) Thermoluminescence of quartz and its use in dosimetry. Proc. Firsr Egyptian-British Conf. on Biophysics, Cairo University, Egypt, October 1987, pp. 265-273. Youssef S. K., Adawi A. M. and Badawy Z. M. (1988) Preparation and dosimetric properties of GeS as a radiophotoluminescence dosimetry. Proc. Fourth Conf: Nucl. Sci. Application, Egypt, March 1988, pp. 623630. Youssef S. K., Guirguis L. A. and Shahin N. (1993) Aspects of radiation induced effects of TL mechanisms of natura1 barite for dosimetric utilization. J. Mater. Sci. Lerrs.