Structural and wavelength dependent optical properties of La1-xEuxCoO3 perovskite phosphor

Abstract

The Eu2+/Eu3+ doped LaCoO3 (La1-xEuxCoO3) perovskite phosphors have been prepared using auto-combustion technique. Rietveld structural analysis of X-ray diffraction patterns for all compositions shows rhombohedral crystal structure with R3‾c space group. The lattice parameters and unit cell volume increase while the crystallite size and particles size decrease with the increase of Eu ion concentration. The HRSEM images indicate spherically shaped particles elongated to each other. The EDS analysis confirms the presence of La, Eu, Co and O elements in the phosphor with good compositional homogeneity. The XPS spectra reveal the presence of (Co2+, Co3+) and (Eu2+, Eu3+) ions along with the oxygen vacancies in the phosphor. The optical band gap of LaCoO3 phosphor decreases with the increase of Eu ion concentration. The photoluminescence excitation spectra of La1-xEuxCoO3 phosphors contain the excitation peaks at 338, 355, 374, 394, 450 and 467 nm. The La1-xEuxCoO3 phosphors give multicolor emissions in the green, yellow and red regions upon 355, 374, 394, 450 and 467 nm excitations. The photoluminescence intensity of La1-xEuxCoO3 perovskite phosphors is optimized at 1 mol% concentration of Eu ion. Due to existence of Co2+ and Co3+ ions in the La1-xEuxCoO3 perovskite phosphors, the Eu3+ ion converts into Eu2+ ion, which gives the blue, green and red emissions. The CIE diagram verifies the color tunability in La1-xEuxCoO3 perovskite phosphors. Therefore, the La1-xEuxCoO3 perovskite phosphors may be very useful in display devices, white light emitting diodes (LEDs) and solid state lighting.