Cd4REO(BO3)3 (RE = Sm, Eu, Tb): three new cadmium–rare earth oxyborates with both good NLO and luminescence properties

Three nonlinear optical materials Cd4REO(BO3)3 (RE = Sm, Eu, Tb) have been synthesized through high-temperature solid-state reactions. In their crystal structures, Cd(1)O8 and Cd(2)O6 polyhedra are interconnected via sharing edges and corners into a 3D anion framework with two types of tunnels based on 4- and 7-membered rings; the BO3 groups are grafted into the above-mentioned types, creating new tunnels based on Cd4B3 seven-membered rings, which are filled by RE3+ cations. Powder SHG measurements revealed that the Cd4REO(BO3)3 (RE = Sm, Eu, Tb) samples display SHG signals that are approximately 1.2, 5.6 and 1.5 times that of the KDP sample. In addition, Cd4EuO(BO3)3 and Cd4TbO(BO3)3 emit red and green light, respectively. The lifetime of the Eu(5D0) state for λex,em = 464, 610 nm in Cd4EuO(BO3)3 is measured to be about 1.43 ms whereas the lifetime of the Tb(5D4) state for λex,em = 376, 543 nm in Cd4TbO(BO3)3 is measured to be about 1.01 ms.