SYNTHESIS AND LUMINESCENCE OF CERIUM DOPED KSrY(BO3)2

Abstract

Abstract. Introduction. 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 KSrY_0.95(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 KSrY_0.95(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 KSrY_0.95(BO₃)₂:0.05Ce³⁺are: a = 9.2861(23) Å, b = 5.3654(6) Å, c = 6.5854(14) Å, V = 289.7(1) ų. 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 ²F_7/2 → 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 KSrY_0.95(BO₃)₂:0.05Ce³⁺ sample has been found for 3 hours after its annealing.