We carried out extensive studies to identify, synthesize, purify and grow crystals of a novel class of halides for nonlinear optical applications. Several compounds such as Tl3PbBr5, Tl4PbI6, Tl4HgI6 and Tl3PbI5, were studied. Optical quality was evaluated by fabricating cm size crystals. The homogeneity of bulk crystal was evaluated by studying transparency, bulk optical distortion and X-ray rocking curve and 2theta-omega scans. Compounds of Tl3PbBr5 composition showed self-poling during the growth. We demonstrated that these halides have transparency from visible to Far-IR wavelength region. (C) 2004 Elsevier B.V. All rights reserved.