| With the development of neutron detection and imaging technologies in the fields of nuclear energy,material analysis and detection.Neutron detection materials have been paid more and more attentions.High neutron detection efficiency and neutron/gamma discrimination abilities,good environmental stability and low preparation cost are main research directions for developing new neutron detection materials.Liquid scintillators are a kind of widely used neutron detection materials because of their good time response and high neutron/gamma discrimination abilities,but their environmental stabilities are poor.Although amorphous scintillators,such as plastic and glass scintillators,are easy to be prepared,their light output efficiency is low.The crystal solid scintillator has high detection efficiency,but the expense for preparation single crystal,especially with large size,is very high.In view of this,a new kind of neutron detection materials which may possess high light yields,short response time and high stabilities was proposed,which utilize rare earth element doped Y3Al5O12(YAG)transparent ceramics as the matrix and the doped 6Li as the nuclear reaction element.In this study,6Li and rare earth elements(RE:Ce,Eu,Gd)co-doped YAG transparent ceramics were prepared by solid state reaction method.Effects of compositions and the preparation process on the microstructures and the optical properties of transparent ceramics were systematically studied.The radiation intensities of the typical neutron source(252Cf source)and gamma ray source(137Cs)were detected using this new kind of neutron detection materials.The main results are as follows:1)6Li,RE co-doped YAG transparent ceramics with uniform microstructure and no obvious porosity and other defects were successfully prepared by solid state reaction.The preparation process,especially the sintering temperature,has obvious influence on microstructures and optical properties of the YAG transparent ceramics.At the same time,the addition of tetraethyl ortho-silicate(TEOS)plays an important role in reducing the loss of 6Li during the sintering process for this kind of ceramics.2)For Ce3xY3(1-x)Al5O12 ceramics doped with 5 at.%6Li,the lattice distortion of YAG increases with the increase of Ce3+ concentration,and the light transmittance of the 6Li:Ce3xY3(1-x)Al5O12 transparent ceramics decreases from 82%(x=0.001)to 67%(x=0.02).At the same time,the intensities of the crystal field around Ce3+ ions increase,which leads to the increasing of the division degree for 5d electron level of Ce3+ ions,and the decreasing and broadening of the excitation peak's intensities.The emission spectra with the emission peaks in the range of 523-542.5 nm showed a red-shift,which can match well with the photomultiplier tube.As for 6Li doped Ce0.003Y2.997Al5O12 transparent ceramics,the light transmittance and excitation intensities will enhance and the emission intensities will decrease with the increase of the 6Li content.3)In the Eu3xY3(1-x)Al5O12 ceramics doped with 5 at.%6Li,Eu demonstrates two valence states of +2 and +3 at the same time.The as-sintered Eu3,Y3(1-x)Al5O12 ceramics appear blue because the Eu element exist in the ceramics mainly in the form of Eu2+ ions.But after annealing,most of the Eu2+ ions convert to the Eu3+ ions,causing the samples with colorless and transparent,and their light transmittances will recede and the emission intensity will enhance with the increase of the Eu content.4)For Gd3xCe0.003y3(1-x)Al5O12 ceramics doped with 5 at.%6Li,the light transmittances will decrease,and the excitation and emission intensities will recede with the increase of the Gd3+ content with the emission peaks red-shifted obviously.After annealing,the lattice distortion is reduced due to the large number of oxygen vacancies disappear,which results in a significant improvement for the optical properties of 6Li,Gd,Ce:YAG transparent ceramics.5)Both 6Li,Ce:YAG and 6Li,Eu:YAG transparent ceramics can response to neutron,but the former shows a better neutron detection and n-y discrimination abilities than the latter.The 6Li,Gd,Ce:YAG transparent ceramic shows a good neutron response,but the ability of n-y discrimination is poor. |
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