Eu掺杂KNN陶瓷的制备及可调性发光研究

doi:10.15541/jim20190106

摘要/Abstract

摘要：

稀土离子掺杂铁电陶瓷是一类新型光致变色材料, 在光开关、光信息存储等领域具有潜在应用价值。本研究采用水热法制备了(K_0.5 Na_0.5)_1-_xEu_xNbO₃(KNN:xEu)前驱体粉体, 随后利用高温烧结得到对应陶瓷样品。在465 nm激发下, 观察到615 nm处有强的红色发光, 对应于Eu ³⁺的 ⁵D₀→ ⁷F₂跃迁。通过紫外光照射, KNN:Eu陶瓷从乳白色变为深灰色。随后经过200 ℃加热10 min, 着色陶瓷又变回到初始颜色, 显示出良好的光致变色行为。紫外照射和反复加热循环可以有效调控该陶瓷的发光强度。且经过多次循环之后, 发光强度没有明显衰减。在紫外光照射下, KNN:0.06Eu陶瓷发光强度的可调比(ΔR_t)高达83.9%, 说明发光具有良好的可调性。进而结合发光中心和色心之间的能量转移, 对KNN:Eu陶瓷的光致变色和发光机理进行了解释。

关键词: K_0.5Na_0.5NbO₃(KNN), 发光, 光致变色

Abstract:

Rare-earth doped inorganic ferroelectrics are considered as novel photochromic materials, with potential applications for optical switch and information storage (K_0.5Na_0.5)_1-_xEu_xNbO₃(KNN:xEu) ceramics were prepared by high temperature calcination, with precursor powder obtained by hydrothermal method. Strong red emission at 615 nm was observed which corresponds to the ⁵D₀→ ⁷F₂ transition of Eu ³⁺ under excitation of 465 nm. Under UV light irradiation for 3 min, the color of the ceramics turned from milky white to dark gray. The colored samples returned to the original color when heated at 200 ℃ for 10 min, showing strong photochromic behavior. Meanwhile, the luminescence intensity of Eu ³⁺ can be tuned without obvious degradation by alternating UV light and heat stimulus. Upon UV light irradiation, large luminescence modulation ratio (ΔR_t) up to 83.9% was achieved for KNN:0.06Eu, indicating good luminescence switching behavior. A possible mechanism for non-radiative energy transfer from the luminescent center to the color center was proposed according to their luminescent behavior.

Key words: K_0.5Na_0.5NbO₃(KNN), luminescence, photochromism

中图分类号:

TQ174

王梦慧,申慧,田甜,鲜琴,徐家跃,金敏,贾润萍. Eu掺杂KNN陶瓷的制备及可调性发光研究[J]. 无机材料学报, 2020, 35(2): 236-242.

WANG Meng-Hui,SHEN Hui,TIAN Tian,XIAN Qin,XU Jia-Yue,JIN Min,JIA Run-Ping. Preparation and Tunable Luminescence of Eu Doped KNN Ceramics[J]. Journal of Inorganic Materials, 2020, 35(2): 236-242.

图/表 6

Fig. 1 XRD patterns of the precursor powders synthesized at 200 ℃ for 12 h (K+/Na+=3:1) with different [OH-] concentrations (a), XRD patterns of KNN:xEu (x=0.02, 0.04, 0.06, 0.08, 0.10) powders synthesized at 200 ℃ for 12 h (K+/Na+=3:1, [OH-]=11 mol/L) (b) and zoomed XRD patterns from (b) within 30°-33° (c)

Fig. 2 SEM image of KNN:0.06Eu ceramics synthesized at 1140 ℃ for 4 h

Fig. 3 Excitaion (λem=618 nm) spectra of the KNN:0.06Eu ceramics and emission (λex=465 nm) spectra of KNN:xEu ceramics at room temperature (a) and the dynamic decay curves on Eu3+ concentrations for KNN:Eu samples under 465 excitation (b)

Fig. 4 Reflectance spectra for the KNN:0.06Eu by UV light irradiation (0 s, 30 s, 60 s, 2 and 3 min) (a), difference absorption (Δabs) spectra for the KNN:0.06Eu by UV irradiation 3 min with inset showing photographs of color changes of ceramic before and after UV irradiation (b), the Δabs vs Eu concentration (c) and reflectance intensity changes (d) of KNN:0.06Eu by alternating UV irradiation and heat treatment

Fig. 5 Changes of emission spectra (λex=465 nm) of KNN:0.06 Eu ceramics before and after UV irradiation for 3 min (a), luminescence switching ratio (ΔRt) at 615 nm as a function of Eu concentration (b) and ΔRt of KNN:0.06Eu ceramics by alternating UV light irradiation and thermal stimulus for 7 cycles (c)

Fig. 6 Luminescence modulation ratio (ΔRt) as a function of irradiation time under different irradiation wavelengths (a) and schematic diagram of luminescence modulation upon photochromic reactions for KNN:xEu ceramics (VO is oxygen vacancy, and VA is K and Na vacancy) (b)

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