Ag4Hg(SeO3)2(SeO4): a novel SHG material created in mixed valent selenium oxides by in situ synthesis

Abstract

Explorations of new second harmonic generation materials in Ag+-Hg2+/Bi3+-selenites systems afforded three new silver selenium oxides, namely, Ag4Hg(SeO3)2(SeO4) (1), Ag2Bi2(SeO3)3(SeO4) (2) and Ag5Bi(SeO3)4 (3). They exhibit flexible crystal chemistry. Compounds 1 and 2 are mixed valence selenium oxides containing Se(IV) and Se(VI) cations simultaneously. Compounds 1 and 3 exhibit a 3D open framework with 4-, 6- and 8-member polyhedral ring tunnels along a, b and c axes. Compound 1 crystallized in a polar space group and could display a subtle frequency doubling efficiency about 35% of the commercial KH2PO4 (KDP). UV-vis-NIR spectra reveal that compounds 1–3 are wide-band semiconductors with the optical bandgaps of 3.11, 3.65, 3.58 eV respectively. Theoretical calculations disclose that compounds 2 and 3 are indirect band gap structures and their bandgaps are determined by Ag, Bi, Se and O atoms together.