SYNTHESIS AND LUMINESCENCE OF CERIUM DOPED KSrY(BO3)2

The rare-earth borate compounds are widely used in various fields of science and technology as solid-state lasers, LEDs, and plasma panels. Development of blue emitting phosphors typically involves doping with cerium ions various matrices, exhibiting high photoluminescence quantum yields for LEDs. However, the main problem of such compounds, in addition to the concentration quenching, is the presence in the matrix of both the trivalent Ce3+ and tetravalent Ce4+ states of cerium ions. The goal. Study of the luminescent properties of the new KSrY0.95(BO3)2:0.05Ce3+ compound. Experimental. New phosphors based on complex borate KSrY(BO3)2 doped with cerium ions have been obtained by the solid-phase synthesis. The mixture of the starting materials after grinding in an agate mortar has been calcined at 700°C in a platinum crucible for 12 hours. The calcination temperature has been increased in steps of 50°C with re-ground of the mixture at each stage. The KSrY0.95(BO3)2:0.05Ce3+sample has been annealed in hydrogen at 900°C for 8 hours. Results and discussion. The X-ray phase analysis has shown that the new compound crystallizes in the monoclinic space group P21/m. The calculated unit cell parameters for KSrY0.95(BO3)2:0.05Ce3+are: a = 9.2861(23) Å, b = 5.3654(6) Å, c = 6.5854(14) Å, V = 289.7(1) Å3. In the crystal structure of KSrY(BO3)2, each B atom is connected to three O atoms, forming a BO3 triangle. The planar groups (BO3)3 are distributed layer by layer in the plane. The Y atoms are surrounded by six oxygen atoms, forming an octahedral structure and occupying interlayer positions.Ce3+ ions in the crystal lattice mainly replace the Y+3positions based on the similarity of the ionic radius and valency of Y+3 (r = 0.90 Å, CN = VI), Ce3+ (r = 1.01 Å, CN = VI). Conclusion. At a wavelength of 440 nm, the excitation spectrum exhibits one absorption band with the 2F7/2 → 5D1 energy transition, which corresponds to the excitation of the cerium ion from the ground state to the excited state. A decrease in the luminescence intensity of the KSrY0.95(BO3)2:0.05Ce3+ sample has been found for 3 hours after its annealing.