K 7 MgY 2 (B 5 O 10 ) 3 : A novel ultraviolet nonlinear optical crystal based on the [B 5 O 10 ] functional unit

A high-performance ultraviolet (UV) nonlinear optical (NLO) material requires three essential characteristics: a short UV absorption edge, a strong secondharmonic generation (SHG) response, and favorable NLO coefficients. In this study, a novel rare-earth borate compound with the formula K 7 MgY 2 (B 5 O 10 ) 3 was successfully synthesized using a high-temperature solution method combined with chemical cosubstitution. The crystal adopts a non-centrosymmetric (NCS) structure (space group R32) and exhibits an SHG intensity 1.3 times that of potassium dihydrogen phosphate (KDP) under 1064 nm laser irradiation. Its UV cutoff edge is determined to be 290 nm, demonstrating exceptional potential for UV optical applications. Combined experimental and theoretical analyses reveal that the synergistic interplay between polarizable [B 5 O 10 ] groups and heterovalent K + /Mg 2+ /Y 3+ substitution underpins its superior NLO performance.