A Model of New VUV NLO Materials Based on Borate: A Novel Noncentrosymmetric Borophosphate Compound Be₃BPO₇

<jats:title>ABSTRACT</jats:title><jats:p>A favorable borate anionic group can be selected as the basic structural unit for VUV NLO materials, in terms of the properties of known inorganic NLO crystals and the features of their anionic groups, based on anionic group theory from SHG coefficients, UV absorption edge and moderate birefringence. Considering the coordination chemistry of atoms in some inorganic compounds, and the relationship between a noncentrosymmetric structural arrangement and the composition of compounds, a suitable theoretical model that aids the search for new VUV NLO materials has been proposed. The model compounds, formulated as M<jats:sub>x</jats:sub>A<jats:sub>1,2</jats:sub>(BO<jats:sub>3</jats:sub>)<jats:sub>1,2</jats:sub>O<jats:sub>y</jats:sub>, may be prospective candidates for new VUV NLO materials considering their SHG coefficients, UV absorption edge, and moderate birefringence. The model suggests that investigation for a new VUV NLO material would be profitably conducted by focusing on boroberylate, boroaluminate, and borophosphate, on the basis of anionic group theory. For example, a novel noncentrosymmetric beryllium borophosphate compound, Be<jats:sub>3</jats:sub>BPO<jats:sub>7</jats:sub> was synthesized by solidstate reaction. Microcrystalline Be<jats:sub>3</jats:sub>BPO<jats:sub>7</jats:sub> has a hexagonal system and contains the BO<jats:sub>3</jats:sub> anionic group as its basic structural unit, which should play an important role for SHG coefficients. In fact, Be<jats:sub>3</jats:sub>BPO<jats:sub>7</jats:sub> powder was found to have a significant SHG effect.</jats:p>