The new nonlinear optical (NLO) crystal LuxLayScz(BO3)(4) (X + Y + Z = 4) of trigonal phase has been synthesized by doping with Lu in monoclinic LaSC3(BO3)(4). Phase boundaries have been established in the determination of the x, y, z composition parameters that define the existence region of the trigonal huntite-type structure. From single-crystal X-ray diffraction measurements, the member Lu0.66La0.95SC2.39(BO3)(4) has been found to crystallize in space group R32 with cell dimensions a = 9.87420(1 0) and c = 8.0696 (7) angstrom. Large single crystals have been grown by a high-temperature top-seeding solution method. The UV absorption edge for polished pieces was found to be at a wavelength shorter than 200 nm. Sellmeier equations were established on the basis of the refractive indices measured by the method of auto-collimation. From modeling and optical measurements on powders, the (NLO) coefficient d(11) has been determined to be 1.3 pm/V. (c) 2007 Elsevier B.V. All rights reserved.