A new yttrium borate compound K(3)y(3)(BO3)(4) has been obtained in the K2O-Y2O3-B2O3 ternary system. Its structure, determined from single crystal X-ray diffraction data, shows that it belongs to space group P2(1)/c with unit cell dimensions of a = 10.4667(16) angstrom, b = 17.361(3) angstrom, c = 13.781(2) angstrom and beta = 110.548(8)degrees. The structure consists sheets of [Y8B8O24](infinity) linked by out of sheet BO3 groups and Y ions to form a three-dimensional framework. The luminescent properties of Eu3+ and Tb3+ doped K3Y3(BO3)(4) materials have also been studied. (C) 2007 Elsevier Ltd. All fights reserved.