调控Al2O3晶型控制MgAl2O4:Mn4+荧光粉中Mn价态研究

doi:10.15541/jim20200386

无机材料学报 ›› 2021, Vol. 36 ›› Issue (5): 513-520.DOI: 10.15541/jim20200386

所属专题：【虚拟专辑】LED发光材料

调控Al₂O₃晶型控制MgAl₂O₄:Mn⁴⁺荧光粉中Mn价态研究

王兆武¹(), 姬海鹏¹(), 王飞翔¹, 侯星慧¹, 易莎莎¹, 周颖¹, 陈德良¹^,²()

1.郑州大学材料科学与工程学院, 郑州 450001
2.东莞理工学院材料科学与工程学院, 东莞 523830

收稿日期:2020-07-09 修回日期:2020-08-26 出版日期:2021-05-20 网络出版日期:2021-04-19
通讯作者: 姬海鹏, 讲师. E-mail: jihp@zzu.edu.cn; 陈德良, 教授. E-mail: dlchen@zzu.edu.cn
作者简介:王兆武(1985-), 男, 博士研究生. E-mail:smithen0504@gs.zzu.edu.cn
基金资助:
国家自然科学基金(51902291);中国博士后科学基金(2019M662524);河南省博士后科研项目(19030025);河南省高校科技创新团队(19IRTSTHN028)

Valence State Control of Manganese in MgAl₂O₄:Mn⁴⁺ Phosphor by Varying the Al₂O₃ Crystal Form

WANG Zhaowu¹(), JI Haipeng¹(), WANG Feixiang¹, HOU Xinghui¹, YI Shasha¹, ZHOU Ying¹, CHEN Deliang¹^,²()

1. School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
2. School of Materials Science and Engineering, Dongguan University of Technology, Dongguan 523808, China

Received:2020-07-09 Revised:2020-08-26 Published:2021-05-20 Online:2021-04-19
Contact: JI Haipeng, lecturer. E-mail: jihp@zzu.edu.cn; CHEN Deliang, professor. E-mail: dlchen@zzu.edu.cn
About author:WANG Zhaowu(1985-), male, PhD candidate. E-mail:smithen0504@gs.zzu.edu.cn
Supported by:
National Natural Science Foundation of China(51902291);China Postdoctoral Science Foundation(2019M662524);Post Doctoral Research Sponsorship in Henan Province(19030025);Program for Innovative Research Team (in Science and Technology) in University of Henan Province(19IRTSTHN028)

摘要/Abstract

摘要：

Mn⁴⁺激活红光荧光粉是白光半导体发光二极管(wLEDs)领域当前研究热点之一。Mn⁴⁺离子²E→⁴A₂跃迁在铝酸盐中的最短发光波长是在MgAl₂O₄中实现的651 nm发光, 由于其结构中含有形成四面体或八面体配位的两种阳离子格位(Mg²⁺/Al³⁺), 易造成所掺杂锰元素存在多种价态(+2/+4/+3等)。本研究通过改变起始原料中Al₂O₃的晶型(γ/α比例)及退火处理来调控锰离子在MgAl₂O₄晶格中的占据格位, 对其主要存在价态实现调控。采用荧光光谱和紫外-可见-近红外漫反射光谱技术来表征所合成荧光粉中Mn离子的价态及其演变。研究发现, 高α/(α+γ)比铝源促进Mn²⁺形成, 而低α/(α+γ)比铝源促进Mn⁴⁺形成。通过使用高活性纳米γ-Al₂O₃为铝源, 有效抑制了锰离子在MgAl₂O₄中Mg²⁺格位的占据及Mn²⁺离子的形成, 经空气中1550 ℃保温5 h的一次高温热处理即可制备出在可见光区只有Mn⁴⁺红光发光的高纯高亮度MgAl₂O₄:Mn⁴⁺荧光粉。氧化铝晶型影响锰离子掺杂格位和掺杂价态的本质规律是: 氧化铝活性决定实际固溶掺杂反应步骤, 进而影响锰离子掺杂格位和价态。本研究提出的反应步骤调控作为反应气氛、电荷补偿剂、反应温度三种调控方法外的一种新方法, 为Mn⁴⁺激活铝酸盐荧光粉中锰离子掺杂价态调控提供了新思路。

关键词: Mn⁴⁺, 白光LEDs, 红光荧光粉, 价态调控

Abstract:

Mn⁴⁺ activated red phosphor is one of the current research hot-spots in the field of white light emitting diodes (wLEDs). The shortest emission of Mn^{4+ 2}E→⁴A₂ transition in aluminate is 651 nm realized in MgAl₂O₄, but the doped manganese ions exists in multiple valence states (+2/+4/+3, etc.) due to the fact that there exist two cationic sites (Mg²⁺/Al³⁺) forming tetrahedron or octahedron coordination in the spinel structure. In this study, variation of the Al₂O₃ polymorphs (γ/α ratio) in the starting materials and post-annealing were used to control the doping sites and valence state of manganese ions in the MgAl₂O₄ structure. The results show that a high α/(α+γ) ratio of starting Al₂O₃ favors the formation of Mn²⁺ while a low α/(α+γ) ratio of starting Al₂O₃ favors the formation of Mn⁴⁺ dopant. By using highly active nano-γ-Al₂O₃ as the Al³⁺-bearing source, the occupancy of manganese ions in the Mg²⁺ site and the formation of Mn²⁺ valence state were effectively suppressed. Bright and pure MgAl₂O₄:Mn⁴⁺ phosphors in which only the red luminescence from Mn⁴⁺ was observed in the visible spectral region were successfully prepared via once heat treatment at 1550 ℃ for 5 h in air. The intrinsic reason for the dependence of manganese doping valence state on the Al₂O₃ polymorph lies in that the reactivity of Al₂O₃ determined the sequences of doping reactions and then the doping site/valence of manganese ions in MgAl₂O₄:Mn. All the above data demonstrated that the control of reaction sequences was a new method to regulate the valence state of manganese in aluminate phosphors.

Key words: Mn⁴⁺, white LEDs, red-emitting phosphor, valence state control

中图分类号:

TQ174

王兆武, 姬海鹏, 王飞翔, 侯星慧, 易莎莎, 周颖, 陈德良. 调控Al₂O₃晶型控制MgAl₂O₄:Mn⁴⁺荧光粉中Mn价态研究[J]. 无机材料学报, 2021, 36(5): 513-520.

WANG Zhaowu, JI Haipeng, WANG Feixiang, HOU Xinghui, YI Shasha, ZHOU Ying, CHEN Deliang. Valence State Control of Manganese in MgAl₂O₄:Mn⁴⁺ Phosphor by Varying the Al₂O₃ Crystal Form[J]. Journal of Inorganic Materials, 2021, 36(5): 513-520.

图/表 7

图1 nano-γ-Al2O3原料和其在1400 ℃保温5 h后以及MgO原料的XRD图谱(同时给出γ-Al2O3和α-Al2O3及MgO的标准PDF衍射卡片)(a), 不同α/(α+γ)比例Al2O3为铝源时所合成MgAl2O4:Mn的XRD图谱(b), 不同α/(α+γ)比例Al2O3为铝源时所合成MgAl2O4:Mn的荧光光谱(λex=365 nm)及α/(α+γ)=50%铝源所合成荧光粉检测520和651 nm发光的激发光谱(c)

Fig. 1 XRD patterns of the raw and heat-treated (at 1400 ℃ for 5 h) nano-γ-Al2O3 (the standard patterns for γ-Al2O3 and α-Al2O3 are also given) (a), XRD patterns of MgAl2O4:Mn phosphors synthesized using alumina sources with different α/(α+γ) ratios (b), and photoluminescence emission spectra of the MgAl2O4:Mn synthesized using alumina sources with different α/(α+γ) ratios (λex=365 nm) and the excitation spectra monitored for 520 and 651 nm emission of MgAl2O4:Mn with α/(α+γ)=50% (c)

图2 不同α/(α+γ)比例的Al2O3为铝源时所合成MgAl2O4:Mn荧光粉在365 nm紫外灯照射下的数码照片

Fig. 2 Digital images (λex=365 nm) of the MgAl2O4:Mn phosphors synthesized using the alumina sources with different α/(α+γ) ratios (a) 100%; (b) 75%; (c) 50%; (d) 25%; (e) 0

图3 不同α/(α+γ)比例Al2O3为铝源时所合成MgAl2O4:Mn的紫外-可见-近红外漫反射光谱图

Fig. 3 UV-Vis-NIR diffuse reflectance spectra of the MgAl2O4:Mn synthesized using alumina sources with different α/(α+γ) ratios

图4 不同α/(α+γ)比例Al2O3为铝源时所合成MgAl2O4:Mn的SEM照片

Fig. 4 SEM images of the MgAl2O4:Mn synthesized using alumina sources with different α/(α+γ) ratios (a) 100%; (b) 75%; (c) 50%; (d) 25%; (e) 0

图5 不同α/(α+γ)比例Al2O3为铝源时所合成MgAl2O4:Mn在1000 ℃下保温10 h(a)及其再在1200 ℃下保温10 h(b)的发光光谱(λex=365 nm), 所合成MgAl2O4:Mn荧光粉及其退火处理后发光光谱中I651 nm/I520 nm强度的比值(c)

Fig. 5 Photoluminescence emission spectra (λex=365 nm) of the MgAl2O4:Mn phosphors using the Al2O3 with different α/(α+γ) ratios annealed at 1000 ℃ for 10 h (a), annealed at 1000 ℃ for 10 h and at 1200 ℃ for another 10 h (b), I651 nm/I520 nm ratios calculated from the luminescence spectra of the MgAl2O4:Mn phosphors (both as-prepared and post-annealed) (c)

图6 Al2O3(AR, γ-phase, micro size)为铝源、其他参数保持不变时经1550 ℃保温5 h所得荧光粉的XRD图谱(a)和发光光谱(λex=365 nm)(b)

Fig. 6 XRD pattern (a) and photoluminescence spectrum (λex=365 nm) (b) of the phosphor synthesized at 1550 ℃ for 5 h using Al2O3 (AR, γ-phase, micro size) as the alumina source

表1 调控MgAl2O4:Mn荧光粉中锰离子掺杂价态的途径

Table 1 Methods to regulate the valence state of manganese ion in the MgAl2O4:Mn phosphor

No.	Methods	Results
1	Control of atmosphere	Reducing atmosphere generating green-emitting MgAl₂O₄:Mn²⁺ phosphor^[14,15], while in oxidizing atmosphere generating red-emitting MgAl₂O₄:Mn⁴⁺ phosphor^[7]
2	Control of charge compensator	Deficient MgO generating green-emitting MgAl₂O₄:Mn²⁺ phosphor in the raw materials while excessive MgO generating red-emitting MgAl₂O₄:Mn⁴⁺ phosphor^[16,17]
3	Control of heating temperature	Heating at low temperatures generating red-emitting MgAl₂O₄:Mn⁴⁺ phosphors while heating at higher temperature with longer duration period generating green-emitting MgAl₂O₄:Mn²⁺ phosphor^[7]
4	Control of Al³⁺- bearing source	Highly reactive γ-Al₂O₃ as the Al³⁺-bearing source preferentially producing red-emitting MgAl₂O₄:Mn⁴⁺ phosphor

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调控Al₂O₃晶型控制MgAl₂O₄:Mn⁴⁺荧光粉中Mn价态研究

Valence State Control of Manganese in MgAl₂O₄:Mn⁴⁺ Phosphor by Varying the Al₂O₃ Crystal Form

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