Synthesis, structural and photoluminescence behaviour of novel La2SiO5:Eu3+/Tb3+ nanomaterials for UV-LEDs

Abstract

Trivalent europium and terbium doped La2SiO5 (LSO) phosphors were synthesized at 600 °C via sol-gel combustion technique using nano-silica powder. The as-prepared samples were calcined at 950 and 1050 °C to study the effect of temperature on the structural and luminescence properties of these materials. Diffraction measurements, Fourier transformation infrared study and transmission electron microscopy were applied for the structural examinations of materials. Diffraction patterns of calcined LSO:Eu3+ and LSO:Tb3+ validates the synthesis of monophasic materials similar to undoped La2SiO5 host. The structures of all materials have monoclinic symmetry and P21/c space group. Below 1050 °C calcination temperature, La2SiO5 lattice adopts X1-phase isostructural with Y2SiO5 and Gd2SiO5.The appearance of peaks in infrared spectra at 880−1020 cm−1, analogous to SiO4 tetrahedra, confirms the layered structure of the lattice. Transmission electron micrographs of materials illustrate the spherical nanoparticles of fine size with some conglomeration. Energy dispersive X-Ray spectroscopy (EDS) shows only the peaks corresponding to elements assimilated within the host framework. Photoluminescence characterization of La2SiO5:Eu3+ showed 5D0→7Fj (j = 0, 1, 2 and 3) with a dominant emission peak at 614 nm in the red region of the spectrum due to the 5D0→7F2 transition of Eu3+ ions. The photoluminescence emission spectra (PL) of Tb3+ doped LSO exhibited 5D3→7FJ (J = 3–5) and 5D4→7FJ (J = 3–6) transitions in blue and green region respectively. The dominant peak at 543 nm for 5D4→7F5 transition is accountable for the green emission of Tb3+ doped samples on UV excitation.