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A new nonlinear optical (NLO) material, BiTeBO (BTBO), is successfully grown from high temperature solution method. BTBO crystallizes in a polar space group of P6 with a framework structure composed of [BiO] blocks, with TeO and BO interconnection. It is interesting that in the BTBO structure three types of NLO-active units, including stereochemically active lone pair cations (Bi cations), second-order Jahn-Teller distorted octahedra (TeO octahedra) and π-orbital planar groups (BO groups), simultaneously exist. The additive contribution from these three types of groups results in an extremely large second harmonic generation (SHG) response in BTBO (about 20 times that of KDP), exhibiting the largest SHG effect among the known borate NLO materials. The enhancement of the nonlinear optical property is elucidated by the first-principles analysis.

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A new birefringent Ba 2 Mg(B 3 O 6 ) 2 (BMBO) crystal with dimensions of 41 6 27 6 9 mm 3 has been grown from a stoichiometric melt. The structure of BMBO, determined from single-crystal X-ray diffraction data, demonstrates that it belongs to the rhombohedral space group R3 ¯with unit cell parameters of a = 7.094(5) A ˚, c = 16.721(15) A ˚and Z = 3. BMBO melts congruently with a melting point of 1000 uC and does not show any phase transitions from room temperature to the melting point. It is found that the BMBO crystal has a wide transmission range (178-3000 nm), large birefringence (Dn = n o 2 n e = 0.2045-0.0767 from 190 nm to 3 mm) and high chemical stability. The BMBO crystal may serve as a unique birefringent crystal for polarizers, beam displacers and beam splitters in the ultraviolet, especially in the deep ultraviolet range. Experimental sectionA BMBO single crystal was grown from a stoichiometric Ba 2 Mg(B 3 O 6 ) 2 melt. High purity starting materials of BaCO 3

Single crystals of the birefringent material Ba 2 Ca(B 3 O 6 ) 2 (BCBO) with dimensions up to 40 × 28 × 10 mm 3 were successfully grown by top-seeded solution growth (TSSG) method from B 2 O 3 −NaF flux. It exhibits high transmittance in the range of 190−3000 nm with UV cutoff of 178 nm, which is much shorter than that (189 nm) of the commercial UV birefringent crystal, the high-temperature phase of BaB 2 O 4 (α-BBO). Meanwhile, BCBO crystal has large birefringence (Δn = n o − n e = 0.2524−0.0862) in the wavelength range from 178 to 3000 nm and without phase transition from room temperature to the melting point. A prototype of Glan−Taylor polarizer made from BCBO crystal showed an optical extinction ratio of 10 4 :1, which is comparable to those of commercial birefringence crystals. The experimental results demonstrate that the BCBO crystal can be a new promising birefringent crystal for UV, especially the sub-200 nm deep-UV range.

LaSrMnO 4 F has been synthesised and shown to have a staged structure in which the insertion of F atoms into the parent LaSrMnO 4 structure has occurred only in alternate (La,Sr)O rocksalt blocks.