Investigations of vibrational, structural and optical properties of erbium polyphosphate micro-powders

Polycrystallines powders of KEr(PO3)4 are grown by solid state reaction. The obtained powders are identified by X-ray diffraction. This compound crystallizes in the monoclinic system, with space group P21/c. Infrared and Raman spectroscopies are used to identify the titled compound. They show that the present structure based upon polyphosphate long chain. The optical properties of the Er3+ ions in this compound have been investigated in detail based on the crystal structure, particle-size distribution, the diffuse reflectance, the excitation and the emission spectra. The optical band gap energy (Eg ≈ 4.61 eV) has been calculated from the diffuse reflectance by using the Kubelka–Munk function and Tauc’s relation. The emission and excitation spectra show the characteristic emission bands of Er3+ in studied compound. The CIE chromaticity coordinates reveal that this phosphor can be a promising green luminophore for application in LED.