Tw om ixed-metal gallium iodate fluorides,n amely, a-and b-Ba 2 [GaF 4 (IO 3 ) 2 ](IO 3 )(1 and 2), have been designed by the aliovalent substitutions of a-a nd b-Ba 2 [VO 2 F 2 (IO 3 ) 2 ]-(IO 3 )( 3 and 4)i nvolving one cationic and two anionic sites. Both 1 and 2 display large second-harmonic generation responses ( % 6 KH 2 PO 4 (KDP)), large energy band gaps (4.61 and 4.35 eV), wide transmittance ranges ( % 0.27-12.5 mm), and high relevant laser-induced damage thresholds (29.7 and 28.3 AgGaS 2 ,r espectively), whichi ndicates that 1 and 2 are potential second-order nonlinear optical materials in the ultraviolet to mid-infrared. Our studies propose that three-site aliovalent substitution is af acile route for the discovery of good NLO materials.Noncentrosymmetric (NCS) oxide materials have extensively excited academic interest owing to their probable properties with applications in second-order nonlinear optics (NLO) as well as in pyroelectrics,f erroelectrics,a nd piezoelectrics. [1][2][3][4][5][6] To the best of our knowledge,a ne xcellent second-order NLO material should feature al arge second harmonic generation (SHG) coefficient, ahigh relevant laserinduced damage threshold (LDT), appropriate optical transmittance range,m oderate birefringence for achieving phase matching,and good thermal stability.Inaddition, it should be free of moisture and accessible by af acile synthetic method. [7][8][9] Metal iodates currently attract extensive research interest due to their potential outstanding SHG response. [10] Up to now,several effective synthetic routes have been reported for exploring the NCS metal iodates featuring novel crystal structures and remarkable SHG performance,s uch as condensing IO 3 À and IO 4 3À units to form polyiodates, [11][12][13] combining six-or five-coordinate d 0 transition metal (TM) cations (e.g.T i 4+ ,V 5+ ,M o 6+ ,a nd Nb 5+ ) [14][15][16][17][18][19][20][21][22] or metal cations (e.g. Bi 3+ and Pb 2+ ) [23][24][25][26] having as tereochemically active lone-pair (SCALP) with iodates,a nd introducing fluoride anions into iodates. [27][28][29][30][31][32] Anumber of excellent SHG materials have been discovered, for instance,NaI 3 O 8 , [11] Cs 2 I 4 O 11 , [13] Li 2 M(IO 3 ) 6 (M = Ti 4+ ,Sn 4+ ,Ge 4+ ), [33][34][35] A(VO) 2 O 2 (IO 3 ) 3 (A = K, Rb,C s, NH 4 ), [15,20] AMoO 3 IO 3 (A = Rb,C s), [14] BaNbO-(IO 3 ) 5 , [17] BiOIO 3 , [23] PbPt(IO 3 ) 6 , [25] Bi(IO 3 )F 2 , [28] and KBi 2 -(IO 3 ) 2 F 5 , [30] which can produce very strong SHG effects (> 10 KH 2 PO 4 (KDP)).Recently,anumber of new NCS crystals were obtained by the aliovalent substitution of known parent compounds to produce materials with strong SHG response. [36][37][38][39][40][41] For example,S e IV O 3 2À has typically been used as as urrogate for I V O 3 À ,w ith substitution of the oxo anion by ah alide anion (usually fluoride anion) to maintain charge balance.T he first bismuth selenite fluoride,B iFSeO 3 ,w ith the strongest SHG performance of all metal selenites,was designed by aliovalent substitution of laye...

A high conversion efficiency of 11.2% was realized in a low-cost PbS-based segmented thermoelectric module.

To develop new mid-infrared (MIR) nonlinear optical (NLO) materials, which can overcome the low laser damage threshold (LDT) of the commercial MIR-NLO crystals (AgGaS , AgGaSe and ZnGeP ) and simultaneously keep the large NLO susceptibility, is necessary for high-power MIR laser frequency conversion technology. To improve the LDT, a new strategy of increasing lattice stability was adopted. Here, the strongly covalent structural unit of the PS tetrahedron was introduced into AgGaS (AGS), and that led to the isolation of the first compound in Ag -Ga -P -S system, namely, AgGa PS (Cc). It retains a large SHG efficiency (1.0×AGS) with phase-matchable ability, and also exhibits an improved LDT (5.1×AGS), indicating AgGa PS is a new promising MIR-NLO crystal. Moreover, a novel 3D framework of [Ga PS ] , with triangular-shaped channels, as well as interesting single triangular geometry of AgS -both of which are very rare in reported sulfides-was discovered in AgGa PS . Furthermore, theoretical calculations, and lattice energy and thermal expansions analyses suggest that the PS group makes a large contribution to the large SHG efficiency and high LDT.