Sr2-x-yAl2SiO7∶x%Sm3+, y%Li+荧光粉的合成与发光特性研究

doi:10.3964/j.issn.1000-0593(2019)04-1013-05

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Abstract At present, aluminosilicates have attracted extensive attention because of their stable chemical properties and easy availability of raw materials, which have become an effective substrate for luminescent materials. Among them, barium aluminosilicate (Sr₂Al₂SiO₇) belongs to the tetragonal system and has a stable crystal structure. As a commonly used activator, Sm³⁺ has characteristic peaks distributed in the band of 300~750 nm. Some characteristic excitation peaks are located in the near-ultraviolet region and have strong absorption in the near-ultraviolet region. Therefore, using Sr₂Al₂SiO₇ as a matrix and Sm³⁺ as an activator, a red phosphor meeting the LED requirements can be prepared. In this work, a series of Sr_2-x-yAl₂SiO₇∶x%Sm³⁺, y%Li⁺ phosphors were synthesized by high temperature solid phase method. The crystal structure, luminescence properties and internal quantum efficiency of the sample were characterized and measured by X-ray diffraction (XRD), photoluminescence spectroscopy (PL), and absolute quantum efficiency measurement system, and the XRD of the sample was refined and the color purity was calculated. The results show that the synthesized samples are all single-phase Sr₂Al₂SiO₇, and do not cause phase transformation after doping with Sm³⁺ and charge compensator Li⁺. Relative to the other cations Sm³⁺(r=1.079 Å), Li⁺(r=0.920 Å) and the radius of Sr²⁺(r=1.260 Å) are the closest, so the two ions are more easily substituted for the Sr²⁺grid. The two ionic radius is smaller than Sr²⁺ to reduce the crystal structure parameters a, b, c and v of the sample. The best excitation peak of the sample is at 403 nm, which shows a blue shift of 3 nm compared to the excitation peak of Ca₃Y₂(Si₃O₉)₂∶Sm³⁺, indicating that the sample has strong absorption under near-ultraviolet light. That is beneficial for applications in the field of lighting. Under the excitation of 403 nm near-ultraviolet light, it can be seen that the emission peak of Sm³⁺ ions is located at 564 nm (⁴G_5/2→⁶H_5/2) and 601 nm (⁴G_5/2→⁶H_7/2) in the range of 500～750 nm. ), 648 nm (⁴G_5/2→⁶H_9/2) and 713 nm (⁴G_5/2→⁶H_11/2), of which the intensity of the 601 nm emission peak is the largest, which makes the sample appear strong orange red color. The emission peaks are cleaved at 607 and 618 nm because the interaction of the crystal fields causes energy level splitting. The intensity of the emission spectrum of the single-doped Sm³⁺ increases first and then decreases with the increase of the concentration, and reaches the strongest when the doping concentration is 2%. Using the energy transfer critical distance formula proposed by Blasse, the critical distance R_C≈19.734 Å is calculated, which indicates that the concentration quenching is caused by the multi-level interaction between Sm³⁺ ions. According to the Dexter theory, the multipole interaction function θ≈6 is calculated, indicating that the concentration quenching mechanism of Sr_2-xAl₂SiO₇∶x%Sm³⁺ is an electric dipole-electric dipole (d-d) interaction. In order to further increase the luminescence intensity, the charge compensator Li⁺ is doped to balance the internal charge of the crystal. The experimental results show that the optimum doping concentration of Li⁺ is 2%, and the luminescence intensity is increased by 2 times compared with the absence of charge compensator, and the internal quantum efficiency is tested to be 43.6%. Fluorescent pink coordinates are in the vicinity of (0.60, 0.39), located in the orange-red region, with a higher color purity (about 92.2%). The phosphor has potential applications in the red component of trichromatic white LEDs.

Key words：Sr₂Al₂SiO₇∶Sm³⁺; Li⁺; Charge compensator Li⁺; Orange red phosphor

Received: 2018-09-01 Accepted: 2019-01-15

ZTFLH:

O433.4

Corresponding Authors: Aierken Sidike E-mail: aierkenjiang@sina.com

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2019)04-1013-05 OR https://www.gpxygpfx.com/EN/Y2019/V39/I04/1013