BaMoO4:Tb3+ phosphor powders were synthesized with different concentrations of Tb3+ ions using the solid-state reaction method. XRD patterns showed that all the phosphors, irrespective of the concentration of Tb3+ ions, had tetragonal systems with two main (112) and (004) diffraction peaks. The excitation spectra of the Tb3+-doped BaMoO4 phosphors consisted of an intense broad band centered at 290 nm in the range of 230-330 nm and two weak bands. The former broad band corresponded to the 4f8 →4f75d1 transition of Tb3+ ions; the latter two weak bands were ascribed to the 7F2→ 5D3 (471 nm) and 7F6→ 5D4 (492 nm) transitions of Tb3+. The main emission band, when excited at 290 nm, showed a strong green band at 550 nm arising from the 5D4→ 7F5 transition of Tb3+ ions. As the concentration of Tb3+ increased from 1 to 10 mol%, the intensities of all the emission lines gradually increased, approached maxima at 10 mol% of Tb3+ ions, and then showed a decreasing tendency with further increase in the Tb3+ ions due to the concentration quenching effect. The critical distance between neighboring Tb3+ ions for concentration quenching was calculated and found to be 12.3 Å, which indicates that dipoledipole interaction was the main mechanism for the concentration quenching of the 5D4→ 7F5 transition of Tb3+ in the BaMoO4:Tb3+ phosphors.

Red phosphors Ca1-1.5xWO4:Eux3+ were synthesized with different concentrations of Eu3+ ions by using a solid-statereaction method. The crystal structure of the red phosphors was found to be a tetragonal system. X-ray diffraction (XRD) resultsshowed the (112) main diffraction peak centered at 2θ=28.71o, and the size of crystalline particles exhibited an overalldecreasing tendency according to the concentration of Eu3+ ions. The excitation spectra of all the phosphors were composedof a broad band centered at 275nm in the range of 230-310nm due to O2−→W6+ and a narrow band having a peak at 307nmcaused by O2−→Eu3+. Also, the excitation spectrum presents several strong lines in the range of 305-420nm, which areassigned to the 4f-4f transitions of the Eu3+ ion. In the case of the emission spectrum, all the phosphor powders, irrespectiveof Eu3+ ion concentration, indicated an orange emission peak at 594nm and a strong red emission spectrum centered at 615nm,with two weak lines at 648 and 700nm. The highest red emission intensity occurred at x=0.10mol of Eu3+ ion concentrationwith an asymmetry ratio of 12.5. Especially, the presence of Eu3+ in the Ca1-1.5xWO4:Eux3+ shows very effective use of excitationenergy in the range of 305-420nm, and finally yields a strong emission of red light.

Red phosphors of Gd1-xAl3(BO3)4:Eux3+ were synthesized by using the solid-state reaction method. The phasestructure and morphology of the phosphors were measured using X-ray diffraction (XRD) and field emission-scanning electronmicroscopy (FE-SEM), respectively. The optical properties of GdAl3(BO3)4:Eu3+ phosphors with concentrations of Eu3+ ions of0, 0.05, 0.10, 0.15, and 0.20mol were investigated at room temperature. The crystals were hexagonal with a rhombohedrallattice. The excitation spectra of all the phosphors, irrespective of the Eu3+ concentrations, were composed of a broad bandcentered at 265nm and a narrow band having peak at 274nm. As for the emission spectra, the peak wavelength was 613nmunder a 274nm ultraviolet excitation. The intensity ratio of the red emission transition (5D0→7F2) to orange (5D0→7F1) showsthat the Eu3+ ions occupy sites of no inversion symmetry in the host. In conclusion, the optimum doping concentration of Eu3+ions for preparing GdAl3(BO3)4:Eu3+ phosphors was found to be 0.15mol.

Red-orange phosphors Gd1-xPO4:Eux3+ (x=0, 0.05, 0.10, 0.15, 0.20) were synthesized with changing theconcentration of Eu3+ ions using a solid-state reaction method. The crystal structures, surface morphology, and optical propertiesof the ceramic phosphors were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), andphotoluminescence (PL) spectrophotometry. The XRD results were in accordance with JCPDS (32-0386), and the crystalstructures of all the red-orange phosphors were found to be a monoclinic system. The SEM results showed that the size ofgrains increases and then decreases as the concentration of Eu3+ ionincreases. As for the PL properties, all of the ceramicphosphors, irrespective of Eu3+ ion concentration, had orange and red emissions peaks at 594nm and 613nm, respectively. Themaximum excitation and emission spectra were observed at 0.10mol of Eu3+ ion concentration, just like the grain size. Anorange color stronger than the red means that 5D0→7F1 (magnetic dipole transition) is dominant over the 5D0→7F2 (electricdipole transition), and Eu3+ is located at the center of the inversion symmetry. These properties contrasted with those of a redphosphor Y1-xPO4:Eux3+, which has a tetragonal system. Therefore, we confirm that the crystal structure of the host materialhas a major effect on the resulting color.