Discovering new mid-IR nonlinear optical (NLO) materials with high laser damage thresholds and easy crystal growth is an urgent and challenging task. Through cationic substitution of Si4+ in Li2K4(TiO)Si4O12, a noncentrosymmetric and polar titanogermanate material, Li2K4TiOGe4O12 has been successfully synthesized. Physical property measurements indicate that this compound can exhibit a wide transparency range extending from 0.28 to 5.8 mu m, a high laser damage threshold (LDT) of 910 MW/cm(2) (1064 nm, 6 ns, 15 Hz), and a moderate second harmonic generation (SHG) response, similar to 2 X KDP at 1064 nm. More importantly, a high-quality single crystal with a size of 35 X 10 X 7 mm(3) has been grown by a top-seeded solution growth method from a stoichiometric exhibits small anisotropic thermal expansion and desirable specific heat and thermal conductivity. All of these melt. In addition, this compound physical properties indicate that Li2K4TiOGe4O12 is a stable mid-IR NLO material. The discovery of Li2K4TiOGe4O12 also suggests that cationic substitution using heavier elements in the same group is a simple but effective strategy to design new mid-IR NLO oxides.
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