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

Abstract

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 λ_ex,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 λ_ex,em = 376, 543 nm in Cd₄TbO(BO₃)₃ is measured to be about 1.01 ms.