Large Magnetocaloric Effect in Li3K9Gd3(BO3)(7) Crystal Featuring Sandwich-Like Three-Dimensional Framework

A new Gd-based borate crystal, Li3K9Gd3(BO3)(7), has been successfully obtained via the high-temperature solution method using Li2O-K2O-B2O3 self-flux. It crystallizes in monoclinic space group P2/n (no. 10) with lattice parameters a = 11.3454(6) angstrom, b = 9.9881(4) angstrom, c = 11.4467(7) angstrom, alpha = gamma = 90 degrees, beta = 114.782(7)degrees, and Z = 2. Li3K9Gd3(BO3)(7) exhibits an intriguing sandwich-like three-dimensional (3D) framework constructed from [Gd-B-O](infinity) layers, KOn (n = 6 and 8) polyhedra, and LiO4 tetrahedra, in which [Gd-B-O](infinity) layers are built from two types of GdO8 polyhedra and triangular BO3 units. Magnetic measurements showed that Li3K9Gd3(BO3)(7) exhibits a large magnetocaloric effect with -Delta Sm = 39.3 J kg(-1) K-1 at 2.0 K for Delta H = 7 T, which is slightly higher than that of the commercial gadolinium gallium garnet under the same conditions. The powder X-ray diffraction, infrared spectrum, and UV-vis-NIR diffuse reflectance spectrum were also performed to characterize Li3K9Gd3(BO3)(7). The electronic band structures, partial density of states, and refractive indices of Li3K9Gd3(BO3)(7) were investigated via the first-principle calculations.