Effect of growth conditions on the quality of lead bromide crystals

Single crystals of pure and doped lead bromide were grown by the Bridgman method in different convective conditions. The convection level was varied by changing the thermal and solutal Rayleigh number. The homogeneity in refractive index, and hence the optical quality, was estimated by examining the optical distortion, birefringence interferograms, and laser scattering through the crystal. The optical quality of the crystal varied significantly with the variation of convection level during the crystal growth. The critical concentration of the solute was estimated for several values of growth velocity by numerical analysis at the thermal gradient of 20 K/cm.