缺陷态对Y掺杂BaZrO_3的质子导电性的影响

Influence of defect states on proton conductivity of Y-doped BaZrO_3

核能是一种新型能源,其开发和利用对氢同位素分离和纯化提出了迫切要求.BaZrO_3基钙钛矿氧化物是一种有效分离纯化氢同位素的材料,本文采用高温固相法制备了BaZr_(1-x)Y_xO_(3-δ)(0≤x≤0.3)系列样品,射线衍射光谱分析表明Y的最大掺杂浓度在0.24—0.26之间.在600?C干燥氢气气氛下,由电化学阻抗谱测试可知,掺20 mol%Y的BaZr_(1-x)Y_xO_(3-δ)样品电导率可达σ=0.00150 S/m,较BaZrO_3基质材料的电导率高接近两个数量级.利用热释光谱和发射光谱研究了系列样品缺陷类型,结果表明BaZrO_3基质材料存在两种对质子传导有利的氧空位(VO);当掺入Y后,除氧空位之外,样品还出现了带负电的质子俘获型缺陷Y′′_(Zr),且Y'_(Zr)缺陷的数量随着Y掺杂浓度增加而增多;同时出现了缺陷陷阱深度变浅导致对质子俘获能力降低的现象,有利于提高质子导电性.本文通过发射光谱和热释光谱相结合,有效地研究了BaZr_(1-x)Y_xO(3-δ)材料的缺陷类型.

Nuclear energy is a promising new energy to solve energy crisis. Separation and purification of hydrogen isotopes play an important role in the developing and utilizing of nuclear energy. BaZrO3-based oxide is an effective material for the separation and purification of hydrogen isotopes. In this paper, a series of BaZr（1-x）YxO（3-δ）（0 x 0.3） are synthesized by high-temperature solid state reaction method. The raw materials are calcined at 1200？C for 5 h in air. Then the calcined powder is consolidated by an isostatic press and sintered at 1500？C for 48 h in air, using a furnace equipped with aluminum oxide heater. Phase purity and phase structure of the obtained BaZr（1-x）YxO（3-δ） are analyzed by XRD. Results show that the structures of the Ba Zr1 xYxO3 δare consistent with the BaZrO3 diffraction pattern（JCPDS 06-399）. The Y ions are already incorporated into the lattice of BaZrO3, and the maximum doping concentration of Y rangs from 0.24 to 0.26. Besides, the proton conductivity of Y-doped BaZrO3 is determined under hydrogen atmosphere by the electrochemical impedance spectroscopy（EIS）. Experiments show that the BaZr（1-x）YxO（3-δ） with 20 mol% Y has the highest conductivity of 0.0015 S/cm at 600？C which is higher than that of the BaZrO3 matrix material by two orders of magnitude. As the concentration of Y increases, the strain in the crystal structure of BaZrO3 increases, which may be created by the defect of Y-doped BaZrO3. In order to reveal the mechanism of proton conduction in Y-doped BaZrO3, the influence of defect types on proton conduction is also investigated via photoluminescence（PL）and thermoluminescence（TL）. For the BaZrO3 matrix, an asymmetrical broad emission peak at 350 to 650 nm occurs in PL with an excitation light of 334 nm. Analysis of Gaussian decomposition shows that the asymmetrical broad emission peak is created by two kinds of different oxygen vacancies（V O）, which are beneficial to proton conduction. Interestingly,when BaZrO3 is doped with Y, a new emission peak P1 at 388 nm appears owing to the negatively charged Y′Zrof proton-trapping-type defects, which is harmful to the proton conduction in general. TL analysis shows that the number of Y′Zrincreases and the depth of the trap reduce, as the Y concentration increases in BaZr（1-x）YxO（3-δ）（x = 0, 0.05, 0.1,0.2）. Although the Y′Zris noxious for the proton conduction, the proton conductivity of BaZr（1-x）YxO（3-δ）（x = 0, 0.05,0.1, 0.2） can be improved via the increase of the release ability of proton trapping as the depth of trap is reduced.