Chemical engineering of a birefringent crystal transparent in the deep UV range

A new birefringent Ba2Mg(B3O6)(2) (BMBO) crystal with dimensions of 41 x 27 x 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 R (3) over bar with unit cell parameters of a = 7.094(5) angstrom, c = 16.721(15) angstrom and Z = 3. BMBO melts congruently with a melting point of 1000 degrees C 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 (Delta n = n(o) - n(e) = 0.2045-0.0767 from 190 nm to 3 mu m) 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.