Synthesis and characterization of Sm, Dy and Er-doped β-Ca3(PO4)2 phosphors

1 mol% Re2O3-99 mol% Ca-3(PO4)(2) (Re = Sm, Dy and Er) powder samples were prepared by solid-state sintering method. The structural, thermal, vibrational and optical properties were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), Raman and photoluminescence techniques. XRD studies confirm the formation of beta-Ca-3(PO4)(2) with the rhombohedral crystal structure. FESEM images reveal the formation of flake-like agglomerated particles of size in the range of 100-700 nm. DSC analysis shows that beta-TCP -> alpha-TCP structural phase transition occurs at 1286 degrees C, followed by alpha-TCP -> alpha'-TCP transformation at 1469 degrees dC. Raman spectra of the samples show antisymmetric and symmetric stretching and bending vibration bands of P-O linkages. Photoluminescence studies found intense reddish-orange emission in Sm-doped samples, white light emission in Dy-doped samples and yellow emission in Er-doped samples. The luminescence intensity of Sm and Dy-doped beta-TCP samples is found to be significantly higher than that of Er-doped samples.