硅酸盐学报

准等静压制备ANbTeO₆（A=K, Rb）透明陶瓷的结构与光学性能

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李燕 ¹^,² , 赵倩倩 ¹ , 靖正阳 ¹ , 涂兵田 ¹^,² , 王皓 ¹^,²

硅酸盐学报 | 研究论文 2024,52(3): 836-844

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硅酸盐学报 |研究论文 2024 , 52 (3) : 836 -844

准等静压制备ANbTeO₆（A=K, Rb）透明陶瓷的结构与光学性能

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李燕¹^,², 赵倩倩¹, 靖正阳¹, 涂兵田¹^,², 王皓¹^,²

作者信息

^1．武汉理工大学，材料复合新技术国家重点实验室，武汉 430070

^2．湖北隆中实验室，湖北襄阳 441000

通讯作者:

王皓（1969—），男，博士，教授。

作者简介:

李燕（2000—），女，硕士研究生。

Structure and Optical Properties of ANbTeO₆ (A=K, Rb) Transparent Ceramics Prepared by Pseudo-Hot Isostatic Pressing

Yan LI¹^,², Qianqian ZHAO¹, Zhengyang JING¹, Bingtian TU¹^,², Hao WANG¹^,²

Affiliations

^1.State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China

^2.Hubei Longzhong Laboratory, Xiangyang 441000, Hubei, China

Corresponding Author:

WANG Hao (1969-), male, Ph.D., Professor. E-mail: shswangh@whut.edu.cn

LI Yan (2000-), female, Master candidate. E-mail: ly17607162835@163.com

出版时间: 2024-03-20 doi: 10.14062/j.issn.0454-5648.20230620

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摘要

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具有立方晶体结构的缺陷烧绿石ANbTeO₆（A = K, Rb）陶瓷是一类颇具潜力的新型透明陶瓷材料，但RbNbTeO₆透明陶瓷制备鲜见报道，且A位离子对透明陶瓷的结构及其光学性能的影响尚缺乏研究。本工作采用固相反应合成了KNbTeO₆（KNT）和RbNbTeO₆（RNT）单相陶瓷粉体，通过无压预烧结合准等静压烧结制备出了光学性能优良的透明陶瓷，系统比较了二者的光学带隙、折射率与色散、红外截止波长。结合对2种材料的晶体结构分析，发现晶格常数随A位离子半径从10.247 9 Å（KNT）增大为10.258 0 Å（RNT），但（Nb/Te）—O键长变化不大。与KNbTeO₆（2.23 eV）相比，RbNbTeO₆透明陶瓷的带隙减小到2.20 eV，导致可见光吸收边略微红移；分子电子极化率和晶胞体积增大使材料在589.3 nm处的光学折射率从1.973（KNT）上升至2.013（RNT）；（Nb/Te）O₆八面体振动的减弱使RNT的红外截止波长拓宽了约0.3 μm。本研究有助于加深对ANbTeO₆（A = K, Rb）缺陷烧绿石透明陶瓷组成、结构与光学性能关系的认识。

关键词

缺陷烧绿石 / 透明陶瓷 / 准等静压 / 晶体结构 / 光学性能

Abstract

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Introduction

The defect pyrochlore ABB'O₆ with a cubic crystal structure is widely used in photocatalysis, ion exchange, microwave dielectric ceramics and ion conductors. Recently, KNbTeO₆ transparent ceramics with a high density and no secondary phase were prepared by a pseudo-hot isostatic pressing (PHIP) technology. The in-line transmittance of over 80% was obtained in this material, demonstrating potential applications in infrared imaging, windows, and optical lenses, etc.. The optical properties of transparent ceramics are closely related to their composition and structure. ANbTeO₆ (A=K, Rb) compounds have a defect pyrochlore structure, and the alkali metal cations affect the crystal structure and optical bandgap of ANbTeO₆. It is thus important to elucidate the impact of A-site ions on the structure and optical properties of the ANbTeO₆ defect pyrochlore transparent ceramics. This paper was to investigate the composition, structure and optical properties of ANbTeO₆ (A=K, Rb) transparent ceramics.

Methods

KNbTeO₆ and RbNbTeO₆ (abbreviated as KNT, RNT) powders were synthesized via solid-state reaction in air with K₂CO₃ (99.99%), Rb₂CO₃ (99.99%), Nb₂O₅ (99.99%), and TeO₂ (99.99%) as raw materials in a ratio of 1∶1∶2. The synthesized and ball-milled powders were pressed into disks with 20 mm diameter and 3 mm thickness in a uniaxial pressure at 5 MPa, and then cold-isostatically pressed at 200 MPa for 5 min. The green bodies were sintered in air to obtain the pre-sintered bodies, and then the pre-sintered bodies were placed in a model HP D60/0 SPS apparatus (FCT Co., Germany) for PHIP processing. The obtained ceramic samples were ground and finally polished on the both sides.

The phase composition of KNT and RNT powders and ceramics was examined by a model PANalytical X-ray diffractometer with Cu K_α radiation (XRD). The microstructure of powders and ceramics was determined by a model FEG250 field emission scanning electron microscope (FEI Quanta). The refractive indices of the ceramics in a wavelength range of 193-1 690 nm were measured by a model M-2 000 V elliptical polarization spectrometer. The in-line transmittance spectra were collected from the ceramics polished on the both sides with the thickness of 1 mm. The Raman vibration spectra of transparent ceramics were measured by a model LabRAM laser confocal microscopy Raman spectrometer. All the tests were conducted at room temperature.

Results and discussion

The XRD patterns of both powders exactly correspond to KNT and RNT with a cubic defect pyrochlore structure, respectively. The Rietveld method was used to refine the XRD patterns of the powders to obtain the information of crystal structure. Clearly, the lattice constant increases from 10.247 9 Å (KNT) to 10.258 0 Å (RNT) and the cell volume expands from 1 076.24 Å³ (KNT) to 1 079.41 Å³ (RNT) with little change in the length of (Nb/Te)-O bond. The composition and element distribution of the PHIP-ed ceramics with a few residual pores and an irregular grain boundary are not affected by sintering, according to the EDS spectra. The relative density of the both ceramics is 99.78% (KNT) and 99.55% (RNT), respectively. The grain size distribution is narrow, and the average grain size is 417 nm (KNT) and 378 nm (RNT), respectively.

The optical transmission range of two transparent ceramics is 0.5-7.2 μm. The maximum in-line transmittances reach 80.25% (KNT, @2 677 nm) and 80.14% (RNT, @3 876 nm), which are similar to their theoretical values. The optical properties of KNT and RNT transparent ceramics were further discussed through valence electron band transitions, molecular electron polarizability, and lattice phonon vibrations. Compared with KNT, RNT transparent ceramic exhibits a slight red-shift in the absorption edge of visible light because of the reduction of the band gap from 2.23 eV (KNT) to 2.20 eV (RNT). The optical refractive index at 589.3 nm increases from 1.973 (KNT) to 2.013 (RNT) obtained from the fitted Sellmeier equation. The electron polarization of Rb⁺ is greater than that of K⁺, increasing the total molecular electron polarization, and K⁺ has a smaller radius than Rb⁺, expanding the lattice and increased the cell molar volume. The Abbé number of RNT (i.e., 18.86) is slightly lower than that of KNT (i.e., 19.45), indicating that the dispersion of RNT transparent ceramic is greater than that of KNT. Based on the Raman spectroscopy analysis, the high-frequency vibration in RNT shifts towards a low wavenumber, i.e., weakening in (Nb/Te)O₆ octahedral vibration, which broadens the infrared cutoff wavelength of RNT by 0.3 μm.

Conclusions

Pure defect pyrochlores ANbTeO₆ (A=K, Rb) ceramic powders were synthesized via solid-state reaction, and the transparent ceramics with the maximum in-line transmittance of 80% both were fabricated via pressure-less sintering and pseudo-hot isostatic pressing sintering. Based on the crystal structure analysis, the increase in the radius of A-site cations led to the cell expansion with a little change in the length of (Nb/Te)-O bond. Compared with KNT, RNT transparent ceramics had a red-shift in a visible light absorption edge, an increase in refractive index with a slightly higher dispersion, and a wider infrared cutoff wavelength. Defective pyrochlore ANbTeO₆ (A=K, Rb) transparent ceramics had a potential application in miniaturization of mid-infrared lenses and devices with a good optical transparency and a high refractive index in the infrared area.

Key words

defect pyrochlore / transparent ceramics / pseudo hot isostatic pressing / crystal structure / optical properties

引用本文

李燕, 赵倩倩, 靖正阳, 涂兵田, 王皓. 准等静压制备ANbTeO₆（A=K, Rb）透明陶瓷的结构与光学性能. 硅酸盐学报, 2024 , 52 (3) : 836 -844 . DOI: 10.14062/j.issn.0454-5648.20230620

Yan LI, Qianqian ZHAO, Zhengyang JING, Bingtian TU, Hao WANG. Structure and Optical Properties of ANbTeO₆ (A=K, Rb) Transparent Ceramics Prepared by Pseudo-Hot Isostatic Pressing[J]. Journal of the Chinese Ceramic Society, 2024 , 52 (3) : 836 -844 . DOI: 10.14062/j.issn.0454-5648.20230620

基金

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国家自然科学基金(52272072)

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2024年第52卷第3期

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文章信息

doi: 10.14062/j.issn.0454-5648.20230620

接收时间：2023-08-20
首发时间：2026-10-22
出版时间：2024-03-20

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收稿日期：2023-08-20
修回日期：2023-09-25

基金

国家自然科学基金(52272072)

作者信息

^1．武汉理工大学，材料复合新技术国家重点实验室，武汉 430070

^2．湖北隆中实验室，湖北襄阳 441000

通讯作者:

王皓（1969—），男，博士，教授。

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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