Structure and photoacoustic spectra of Ag-doped Cu2SiS3 particles

Ag-doped Cu2SiS3 particles were prepared by the reaction of elements at 800 C for 7 days. Their crystal structure were determined from single crystal X-ray diffraction data. The solid solution limit of Ag atom into Cu atom in Cu2SiS3 was estimated to be 2.0 mol % from the change of unit cell volumes. Crystal structure of 2 mol % Ag-doped Cu2SiS3 was isostructure with monoclinic Cu2SiS3, superstructure of 3 times of sphalerite type. Optical absorption of above particles, whose Ag contents were from. 0.0 to 3.0 mol % against to Cu, was measured by a microphone photoacoustic spectroscopy. Midpoint of main transition on Cu2SiS3 particles was 499 nm (2.48 eV) and an absorption in the IR region was from 710 to 730 cm(-1) corresponding to the activation energy of Cu atom bonded by S atoms. The effect of Ag addition was almost nothing up to the limit of solid solution of 2 mol % Ag, but excess Ag addition caused to a slight shift to a wide gap. So it might be consider to a photoelectric or photocatalytic application by use of sunlight.