ReBe₂B₅O₁₁ (Re = Y, Gd): Rare-Earth Beryllium Borates as Deep-Ultraviolet Nonlinear-Optical Materials

Two novel rare-earth beryllium borates ReBe2B5O11 (Re = Y, Gd) have been discovered. These materials possess a unique structural feature with a platelike infinite ∞(2)[Be2B5O11]3– superlayer, which is first found in beryllium borates. The superlayer can be seen as sandwich-shaped with ∞(1)[B4O8]4– chains linking up with a ∞(2)[Be2BO5]3– sublayer above and below via the B–O–Be bond. Each ∞(2)[Be2B5O11]3– layer is further connected to the neighboring layer through Re3+ cations coordinating with O atoms. Both of these two crystals have very short cutoff wavelengths below 200 nm and exhibit relatively large nonlinear-optical (NLO) effects, indicating their promising applications as good deep-UV NLO crystals.