Effect of Zr4+ Co-doping on Neutron/Gamma Discrimination of Cs2LaLiBr6:Ce Crystals

doi:10.15541/jim20230543

Abstract

Abstract:

Neutron detection technology is widely used in homeland security, nuclear material security detection, and high energy physics, etc. Due to the shortage of ³He resources, it is urgent to develop a novel scintillator that can discriminate neutron and gamma. The Cs₂LaLiBr₆:Ce (CLLB:Ce) crystal has good neutron/gamma discrimination capacity, excellent energy resolution and high light yield, but its neutron/gamma discrimination performance needs further improvement. Here, the CLLB:Ce crystals co-doped with Zr⁴⁺were grown successfully by the vertical Bridgman method. The results of different characterization methods prove that the Zr⁴⁺ was successfully doped into the matrix and did not effect on the structure of host. Meanwhile, no new luminescence center was generated after Zr⁴⁺ doping. The UV decay time is about 27 ns, presenting a fast fluorescence decay. Figure of merit (FOM) of CLLB:Ce crystal is enhanced from 1.2 to 1.5 by co-doping Zr⁴⁺, which means that the neutron/gamma discrimination performance of CLLB:Ce crystals is improved. Combined with the thermal stability and scintillation decay time, relationship between decay time and FOM was also analyzed. The co-doping of Zr⁴⁺ can inhibit shallow electron trap and V_K centers, reduce electron trapping-detrapping process, and greatly increase the probability of Ce³⁺ direct capturing electron, which results in a shorter decay time. Data from this study indicate that the CLLB:Ce crystals exhibit a huge application prospect in the field of neutron/gamma detection.

Key words: scintillation crystal, CLLB:Ce, neutron/gamma discrimination, elpasolite structure

CLC Number:

TQ174

ZHENG Zhongqiu, WEI Qinhua, TONG Yufeng, TANG Gao, YIN Hang, QIN Laishun. Effect of Zr⁴⁺ Co-doping on Neutron/Gamma Discrimination of Cs₂LaLiBr₆:Ce Crystals[J]. Journal of Inorganic Materials, 2024, 39(5): 539-546.

Figures/Tables 10

Fig.1 Pictures (a) and XRD patterns (b) of crystal samples (a) Grown crystal with a size of ϕ10 mm×50 mm and machined crystal sample with a size of ϕ10 mm×5 mm, and (b) XRD patterns of different samples

Table 1 Doping concentration comparison of ICP-MS results and theoretical data

Sample	Co-doping element concentration/(mg·kg^-1)	Actual concentratio/% (in mole)	Raw concentration/% (in mole)
CLLB (Ce, Zr)	990.4075	0.101	0.1

Fig. 2 XPS spectra of co-doped crystal samples (a) Total XPS spectrum of co-doped crystal sample; (b) Fine XPS spectrum of Zr4+

Fig. 3 PLE and PL spectra, X-ray excitation emission spectra and PL decay time curves (a) PLE and PL spectra; (b) X-ray excitation emission spectra; (c, d) PL decay time curves (λex=375 nm, λem=388 nm) of CLLB:1%Ce and CLLB:1%Ce,0.1%Zr samples; Colorful figures are available on website

Fig. 4 PL spectra of CLLB:1%Ce,0.1%Zr (a) PL spectra of CLLB:1%Ce,0.1%Zr at 80-450 K; (b) Normalized curves; (c) Relationship between comprehensive emission intensity and temperature; (d) Fitting line of activation energy; Colorful figures are available on website

Fig. 5 Pulse height spectra and scintillation decay time curves (a, b) Pulse height spectra of CLLB:1%Ce, CLLB:1%Ce,0.1%Zr and NaI:Tl standard sample; (c, d) Scintillation decay time curves of CLLB:1%Ce,0.1%Zr (c) and CLLB:1%Ce (d); Colorful figures are available on website

Fig. 6 PSD patterns (left) and energy spectra (right) (a) CLLB:1%Ce; (b) CLLB:1%Ce,0.1%Zr

Fig. 7 Scintillation decay time fitting curves (a) CLLB:1%Ce; (b) CLLB:1%Ce,0.1%Zr; Colorful figures are available on website

Table 2 Decay time and component proportion of CLLB crystal

Sample	Particle	Fast component/ns	Proportion of fast component photons/%	Slow component/ns	Proportion of slow component photons/%
CLLB:Ce	Neutron	127	94	747	6
CLLB:Ce	Gamma	136	94	789	6
CLLB (Ce, Zr)	Neutron	101	99	540	1
CLLB (Ce, Zr)	Gamma	105	99	570	1

Fig. 8 Schematic representation of scintillation mechanism CB: Conduction band; VB: Valence band

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Effect of Zr⁴⁺ Co-doping on Neutron/Gamma Discrimination of Cs₂LaLiBr₆:Ce Crystals

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