Investigation of the CaO–La2O3–SiO2–P2O5 quaternary diagram. Synthesis, existence domain, and characterization of apatitic phosphosilicates

Abstract The CaO–La 2 O 3 –SiO 2 –P 2 O 5 phase diagram was investigated in order to determine a domain inside which all points correspond to pure apatitic oxyphosphosilicates with the general formula Ca x La y (SiO 4 ) 6− u (PO 4 ) u O t . The prepared compounds were chemically analyzed and then characterized by X-ray diffraction method, infrared absorption, and Raman diffusion spectroscopies. The bands present in the IR and Raman spectra were identified and assigned to the corresponding vibration modes of SiO 4 and PO 4 anions. The Eu 3+ luminescence study of some doped samples was carried out and their color points were determined. The present data show that a continuous solid solution is obtained inside the apatitic defined domain. Among the Eu 3+ -doped samples, the Ca 2 La 8 (SiO 4 ) 6 O 2 :Eu(2%) can be used as a red phosphor.