Noncentrosymmetric cubic thio- and selenogermanates: A0.5M1.75GeQ4 (A=Ag, Cu, Na; M=Pb, Eu; Q=S, Se)

Crystal structure of new selenosilicates Pb1.75M0.5SiSe4 (M=Cu and Ag)

“…The peaks of its X-ray powder diffraction pattern were indexed on the basis of a body-centered cubic lattice with a = 1.44995(2) nm, close to that reported for Pb 1.75 Ag 0.5 GeSe 4 [3]. The crystal structure of the Pb 1.75 Ag 0.5 GeSe 4 selenogermanate was used as a starting model for the crystal structure refinement of the Pb 1.75 Ag 0.5 SiSe 4 selenosilicate.…”

“…Later on, Iyer et al [3] corrected somewhat their earlier results and published an improved structure model for Pb 1.75 Na 0.5 GeS 4 and Pb 1.75 Ag 0.5 GeSe 4 . In the meantime, Poduska et al [4] solved the structure of single-metal thiogermanate ␣-Pb 2 GeS 4 (space group I43d, a = 1.4103 nm) and noted the existence of isomorphic selenogermanate Pb 2 GeSe 4 (a = 1.4573 nm).…”

Laser operated piezoelectricity in Ag0.5Pb1.75GeS4 and Ag0.5Pb1.75GeS3Se crystals

“…The growth of the single crystals with compositions Ag 0.5 Pb 1.75 GeS 4 and Ag 0.5 Pb 1.75 GeS 3 Se up to 70 mm length and 10 mm diameter was reported in detail earlier [3,4]. The experimental set-up for measurements of the photoinduced piezoelectricity versus photoinduced pump energy density is similar to the described in Ref.…”

“…In the Ref. [3] it was reported novel quaternary chalcogenide Ag 0.5 Pb 1.75 GeS 4 and Ag 0.5 Pb 1.75 GeSe 4 crystals. These crystals possess non-centrosymmetric structure (space group I-43d) that indicates likely presence of effects described by third rank polar tensors (second harmonic generation (SHG), linear Pockels phenomenon, piezoelectricity etc.).…”

“…The crystals of the solid solution compositions with higher amount of selenium than 25-30 mol% cannot be easily grown by Bridgman-Stockbarger method due to the primary crystallization of PbSe which was shown in the Ref. [3].…”