Study On The Growth And Optical Properties Of Lead Tungstate

Lead tungstate（PWO） due to its favorable scintillation such as highdensity，short radiation length，the Moliere radius，fast decay time andhigh radiation hardness，as a excellent scintillation crystal，it has beenchosen as a preferred material for the detector at the Large HadronCollider in CERN, PWO has been widely used in high energy physics，medical imaging et al. So as a scintillator it arouses extensive researchersaround the word.In this paper, the growth, annealing, diffusion of ion, PWOmicrocrystal synthesis and optical properties were studied. Parts of theresearch work are described as follows:1. PWO single crystal and (F^-,Y³⁺):PWO were grown by Bridgmanand VGF method.By optimizing the growth parameters, Lead tungstatecrystals were colorless and no inclusions which were obtainedsuccessfully. PWO crystals are the tetragonal stolzite that crystallizes with a scheelite type structure, pure PWO single crystal has a strongabsorption at350nm, but But as the F^-,Y³⁺were doped, the absorption at350nm is decreased, the intensity of (F^-,Y³⁺):PWO luminescence isincreased obviously, the highest luminescence peak has blue shift about10-20nm, the light yield of PWO crystal and a gate width of1000ns canreach32pe/MeV, the luminescence decay time is4.2ns, the light yield of(F^-,Y³⁺):PWO which grown by VGF and Bridgman method and a gatewidth of1000ns can reach50p.e/MeV,65pe/MeV, the luminescencedecay time is7ns,5ns respectively.2. PWO crystal diffused with Ce³⁺or Eu³⁺ions which decreased theintrinsic absorption at350nm, but Cr³⁺diffusion PWO crystal produces astrong absorption band; With the increase of the ions concentration, theintensity of Ce³⁺diffusion PWO and Cr³⁺diffusion PWO luminescenceare decreased obviously, and Ce³⁺diffusion PWO has red shiftphenomenon, the intensity of Eu³⁺diffusion PWO luminescence isenhanced.the light yield of Ce³⁺、Eu³⁺、Cr³⁺diffusion PWO crystal and a gatewidth of1000ns can reach36pe/MeV,46pe/MeV,<10pe/MeV, theluminescence decay time is7ns,5ns respectively.3. The PWO crystal intrinsic absorption at350nm is improved afterdifferent atmosphere annealing, but PWO crystal annealed in rich oxygenenvironment has a strong absorption peak at420nm, the PWO crystal annealed in O₂, N2environment produces red shift phenomenon, theintensity of PWO crystal annealed in C power environment is improvedobviously, but the portion of yellow-green light is increased.The light yield of PWO crystal annealed in O₂, N₂, C powerenvironment and a gate width of1000ns can reach10p.e/MeV,25p.e/MeV,38p.e/MeV, the luminescence decay time is5.2ns,4.5ns,4.4ns respectively.4. The well crystalized lead tungstate microcrystals were obtained bycoprecipitation method, As the increase of PEG-400, the morphology oflead tungstate changed from the tower into a shuttle, the prepared leadtungstate has a broad emission peak between blue and green, but theintensity of fluorescence is decreased.The well crystalized (Ce³⁺, Cl^-):PWO microcrystals were obtainedby ultrasonic-assist method, the morphology of lead tungstate changedfrom blocky into a ribbon as the doping concentration of cerium（III）,chlorine increasing, but the intensity of fluorescence is decreased.