Structure and Photoluminescence Properties of Dy3+ Doped Phosphor with Whitlockite Structure

Abstract

Whitlockite has the advantages of a low sintering temperature, high stability, and a low fabrication cost, and it is widely used as the host for luminescent material. In this study, Ca1.8Li0.6La0.6−x(PO4)2:xDy3+ phosphor was prepared by the high-temperature solid-state method, and its structure, composition, and luminescence properties were systematically studied. The results showed that a new whitlockite type matrix was prepared by replacing Ca2+ in whitlockite with monovalent and trivalent cations. The prepared phosphors belonged to a hexagonal crystal system with a particle size in the range of 5–20 μm. Under the excitation of 350 nm UV light, the samples emitted white light, and there were mainly two stronger emission peaks at 481 nm in the blue band and 573 nm in the yellow band, which correspond to the electron transitions at 4F9/2→6H15/2 and 4F9/2→6H13/2 of Dy3+, respectively. The optimal doping concentration of Dy3+ in Ca1.8Li0.6La0.6(PO4)2 matrix was 0.03 (mol%). The main mechanism of concentration quenching in the sample was dipole–dipole energy transfer. When the temperature was 130 °C, the luminescence intensity of the samples was 78.7% of that at 30 °C, and their thermal quenching activation energy was 0.25 eV. The CIE coordinates of the sample at 30 °C were (0.2750, 0.3006), and their luminescent colors do not change with temperature. All the results indicate that Ca1.8Li0.6La0.6−x(PO4)2:xDy3+ phosphor is a luminescent material with good luminescence performance and thermal stability, which shows a promising application in the field of LED display.

Synthesis and Characterization of Li2MgGeO4:Ho3+

“…The presence of defects in the ceramic host leads to the weakness of luminescent properties. However, the incorporation of alkali ions (Li + or Na + ) might compensate for the charge imbalance, reduce the lattice distortion, and enhance luminescence intensity without creating impurities in the host structure [ 34 , 35 , 36 , 37 , 38 ]. It should be also noted that agglomerates are present in the studied germanate ceramics.…”

Dy3+ doped KCa(PO3)3 phosphor for white light generation: structural and luminescent studies

“…The interaction is computed using the potential energy of each dipole. Concentration quenching results from a substantial energy exchange between activators that happens when the concentration of activators reaches a certain level [36]. The schematic energy level diagram shown in figure 10 illustrates the possible electronic transitions of the Dy 3+ in the KCa(PO 3 ) 3 polyphosphate phosphor [37].…”

“…This energy exchange reduces the amount of luminous energy levels and lessens the intensity of the fluorescence. The three cross-relaxation processes of Dy 3+ are as follows [36]:…”

Ho-SiAlON Ceramics as Green Phosphors under Ultra-Violet Excitations

“…Generally, an increase in the activator concentration should be accompanied by an increase in the intensity of the emitted light due to increased absorption efficiency of the excitation energy. However, in most inorganic phosphors, increasing the concentration of activators inevitably decreases the emission intensity [ 10 , 11 , 12 , 13 , 14 , 15 ], a phenomenon called concentration quenching. Concentration quenching of the emission is attributed to the increased probability of energy migration between the luminescent centers as the distance between the luminescent centers becomes shorter with increasing activator concentration [ 16 ].…”