Crystal structure, thermal behaviour, vibrational spectroscopy and optical properties of new compounds KCa(HAsO)2HO with krohnkite-type chain

摘要

The new krohnkite compound called potassium calcium-bis-hydrogen arsenate dihydrate KCa(HAsO2HO was obtained by hydrothermal method and characterized by X-ray diffraction, infrared spectroscopy, Raman scattering, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis and optical (photoluminescence and absorption) properties. It crystallizes in the triclinic space group P and unit cell parameters , , , , and . The structure of KCa(HAsO2HO built up from this infinite, (Ca(HAsO(HO), was oriented along an axis resulting from the association of CaO octahedra alternating with each two HAsO tetrahedra by sharing corners. Each potassium atom links two adjacent chains by three oxygen atoms of HAsO tetrahedra. TGA and DSC have shown the absence of phase transition. The existence of vibrational modes corresponding to the krohnkite is identified by the IR and Raman spectroscopies in the frequency ranges of 400-4000 and 20-4000 cm, respectively. The photoluminescence measurement show one peak at 507 nm, which is attributed to band-band (free electron-hole transitions) and (bound electron-hole transitions) emissions within the AsO inorganic part.