Ae<sub>3</sub>[TO<sub>3</sub>][SnOQ<sub>3</sub>] (Ae\n= Sr, Ba; T = Si, Ge; Q = S, Se) and Ba<sub>3</sub>[CO<sub>3</sub>][MQ<sub>4</sub>] (M = Ge, Sn; Q = S, Se): Design and Synt

The heteroanionic materials (HAMs) have attracted more\nand more\nattention because they can better balance the functional properties\nof materials. However, their rational structural design is still a\ngreat challenge. Here, by using the antiperovskite Ba<sub>3</sub>S[GeS<sub>4</sub>] as a template and calculating the tolerance factor (<i>t</i>) as a reference, eight heteroanionic oxychalcogenides\nwith balanced properties were finally synthesized by a partially group-substitution\nmethod. Among them, Ba<sub>3</sub>[CO<sub>3</sub>][MQ<sub>4</sub>]\n(M = Ge, Sn; Q = S, Se) are centrosymmetric (CS) crystals and realize\noptimization of band gaps and birefringence. For Ae<sub>3</sub>[TO<sub>3</sub>][SnOQ<sub>3</sub>] (Ae = Sr, Ba; T = Si, Ge; Q = S, Se),\nthanks to the novel [TO<sub>4</sub>SnQ<sub>3</sub>] polyanionic groups\nfor the regulation to the antiperovskite structures and the contributions\nto the nonlinear optical (NLO) properties, they achieve the structural\ntransition from CS to noncentrosymmetry and accomplish an excellent\nbalance among the critical performance parameters as the potential\ncandidates for the infrared NLO materials, including phase-matchable\nbehavior, wide band gaps (<i>E</i><sub>g</sub> = 3.26–3.95\neV), high laser damage threshold (LDT = 3.2–4.4 × AgGaS<sub>2</sub>), suitable birefringence (Δ<i>n</i> = 0.065–0.098@2090\nnm) and sufficiently strong second-harmonic generation responses (about\n0.6–0.9 × AgGaS<sub>2</sub>). Moreover, benefiting from\ncrystallization in the polar space groups, they exhibit ferroelectricity\nand piezoelectricity at room temperature. As far as we know, this\nis the first reported fully inorganic antiperovskite ferroelectric.\nThese demonstrate that our strategy is desirable and can provide some\nunique insights into the development of HAMs or antiperovskite materials\nwith specific functions or structures.