Part III: lithium metasilicate (Li2SiO3)—mild condition hydrothermal synthesis, characterization and optical properties

Li2SiO3 nanopowders were synthesized via a non-stoichiometric 2:3 (S1), 1:3 (S2), 1:4 (S3) and 1:5 (S4) Li/Si molar ratios via hydrothermal reaction for 72 h at 180 C in an aqua solution using Li2CO3 and H2SiO3 as raw materials. The synthesized materials were characterized by powder X-ray diffraction (PXRD) technique and Fourier transform infrared spectroscopy. PXRD data showed that the crystal structure of the obtained materials is orthorhombic with the space group of Cmc21. Also, to investigate the effect of the Li/Si molar ratio on the morphology of the obtained materials, the morphologies of the synthesized materials were studied by field emission scanning electron microscopy. The technique showed that with changing the Li/Si molar ratio from S1 to S4, the morphology of as-prepared samples changed from flower structures to microrod–microsphere and then to a nonhomogenous layer-like structure. Ultraviolet–visible spectra showed that the nanostructure lithium silicate powders had good light absorption properties in the ultraviolet light region. It showed that with changing the Li/Si molar ratio from S1 to S4, the calculated band gap was decreased. Also, cell parameter refinement showed that with changing the Li/Si molar ratio from S1 to S4 the cell parameters decreased. Photoluminescence analysis of the obtained materials was studied at the excitation wavelength of 247 nm. It showed that the emission spectra of the obtained materials had a blue shift from S1 to S4.