K7MgY2(B5O10)3: a novel ultraviolet nonlinear optical crystal based on the [B5O10] functional unit

Abstract

A high-performance ultraviolet (UV) nonlinear optical (NLO) material should possess three essential characteristics: a short UV absorption edge, a strong second-harmonic generation (SHG) response, and favorable NLO coefficients. In this study, a novel rare-earth borate compound with the formula K₇MgY₂(B₅O₁₀)₃ was successfully synthesized using a high-temperature solution method combined with chemical co-substitution. The crystal adopts a non-centrosymmetric (NCS) structure (space group R32) and exhibits a SHG intensity 1.2 times greater than that of potassium dihydrogen phosphate (KDP) under 1064 nm laser irradiation within the particle size range of 38–55 µm. 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 [B₅O₁₀] groups and heterovalent K⁺/Mg²⁺/Y³⁺ substitution underpins its superior NLO performance.