CZOCHRALSKI GROWTH OF LEAD TUNGSTATE SINGLE-CRYSTALS AND THEIR CHARACTERIZATION

Single crystals of lead tungstate scintillator were grown by the Czoch ralski method employing resistive heating system. Variations in the na ture of crystal cracking were observed and are discussed in relation t o seed rotation rate, crystal pulling rate and axial temperature gradi ent. The problem of melt supercooling occurred very often and was over come by carefully adjusting the seed rotation rate. Gradual decrease i n optical quality from the top part of the growing crystal was also ob served and repeated crystallization yielded highly transparent crystal s. Excitation-emission spectra evidenced decrease in emission intensit y for the bottom part of the crystal due to poor optical quality. The perfection of the grown crystals was analysed by differential thermal analysis and etching studies. (C) 1998 Elsevier Science B.V. All right s reserved.