Effect of Element Substitution on Structural Transformation and Optical Performances in I2BaMIVQ4 (I = Li, Na, Cu, and Ag; MIV = Si, Ge, and Sn; Q = S and Se)
journal contributionposted on 06.03.2018, 17:34 by Leyan Nian, Kui Wu, Guijie He, Zhihua Yang, Shilie Pan
In the exploration of new infrared nonlinear optical (IR NLO) materials, element substitution has been developed as an effective way to adjust the structural features and material performances. A series of new IR NLO materials have been discovered in the I–Ba–MIV–Q system (I = Li, Na, Cu, and Ag; MIV = Si, Ge, and Sn; Q = S and Se), and they undergo interesting structural transformation with different element substitution except Li analogues. Herein, we have successfully synthesized three selenides with different space groups (Ag2BaSiSe4: I4̅2m; Ag2BaGeSe4 and Ag2BaSnSe4: I222) in the above system and studied their properties through experimental and theoretical methods. Remarkably, the detailed analysis on the structural changes and properties comparison was also systematically investigated in the I–Ba–MIV–Q system and the results indicate that the distortion degrees of different IQ4 tetrahedra play the critical role to cause the structural transformation with the M or Q elements substitution. More importantly, we have also found that the structural changes have the close relationship with the distance d(I–I) between adjacent I cations in the I2BaSnSe4 system, which makes the four-membered rings formed by edge-sharing BaSe8 units change from the square to rhombus with the increase of d(I–I). The properties comparisons (band gap and NLO effect) in this system have been also systematically studied.