Preparation And Optical Properties Of Novel Gd₂SiO₅ Matrix Crystals

The demand for high-quality optical crystals are increasing.Gd₂Si O₅（abbreviated as GSO）single crystal is an important optical matrix for laser crystals or scintillators.In this thesis,the optical floating zone method has been used to grow GSO:RE single crystals,which can quickly obtain the single crystals.Eu³⁺and Tb³⁺are used as the dopants to discover the new optical applications.Gd₂SiO₅:RE crystal was grown by the optical floating zone method.X-ray diffraction,X-ray rocking curve,infrared spectroscopy,Raman spectroscopy,X-ray photoelectron spectroscopy,scanning electron microscopy,energy dispersive spectrometer to analyze the crystalline nature of Gd₂Si O₅:RE crystals.It is found that high-quality crystals have been made.The crystals have no macroscopic defects.Furthermore,no RE do-pant segregates in the crystal.With the help of the finite simulation,the temperature field and stress field distribution are predicted.The temperature is in mode of taking the melting zone as the symmetrical center along the axial direction,and the melting zone has the highest temperature.Along radial direction,the temperature is uniform.The stress concentrates on the edge of the melting zone.The X-ray diffraction residual analysis results verify the stress distribution prediction.The residual stress value of Gd₂Si O₅:Tb is 209.1Mpa,and the residual stress value of Gd₂Si O₅:Eu single crystal is 224.97Mpa.The residual stress of the optical floating zone made crystal is at the same level as the one obtained by the pulling method.Gd₂SiO₅:Eu crystal has an E_g value as 5.9 e V.It emits orange-red light under 365nm excitation,and bright orange under 254 nm excitation.The fluorescence lifetimes of 595nm(corresponding to Eu³⁺⁵D₀→⁷F₁)and 620nm(corresponding to Eu³⁺⁵D₀→⁷F₂)are 2.8860ns and 3.0639ns,respectively.Gd₂Si O₅:Eu crystal has two thermoluminescence centers,one is Eu³⁺doped center(thermoluminescence peak at102℃with emission wavelength as 585nm,trap depth 0.62e V,frequency factor as2.36×10⁸s^-1),and the other is the intrinsic defect(at 344℃,978nm,1.61e V,3.67×10¹²s^-1).The former center is well linear response forγ-ray dose,and could be applied for radiation dosage measurement.Gd₂SiO₅:Tb crystal has an E_g value as 6.1e V.It gives out blue-green emission(Tb³⁺⁵D_4,3→⁷F_J)under 254nm or 277nm excitation,along with the strongest peak according to Tb³⁺⁵D₄→⁷F₅electronic transition.The strongest emission splits to Tb1（548nm,9 coordinated）and Tb2（553nm,7-coordinated）related to the two substitution positions respectively.The fluorescence lifetimes are 2.703ns and 6.754ns,respectively.Gd₂Si O₅:Tb crystal has good scintillator performance as the absolute light output for662ke V is about 10200 photons/Me V（10%larger than BGO）,the energy resolution is about 8.6%（better than BGO scintillation crystal）,and decay time as 37ns（300ns for BGO）.GSO:Tb crystal is potential for the scintillator.