| Nuclear energy is a promising 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 perovskite oxide is an effective material for the separation and purification of hydrogen isotopes. However, BaZrO3-based compound suffers several problems such as high sintering temperature, long sintering time, low proton conductivity, and unclear proton conductivity mechanism. In this thesis, we attempt to reduce the sintering temperature and time of BaZrO3-based compound by addition of flux, and meanwhile to introduce different defect states in matrix materials. Besides, the influences of defect states on proton conductivity are studied by combination of emission spectra and thermoluminescence spectroscopy.In this thesis, a BaZrO3-based material was prepared via sintering at 1200? for 5 h by a high temperature solid-phase reaction. XRD tests show that a 5mol% excess of BaCO3 did not produce ZrO2 impurity phases. XRD structure refinement indicates that the unit cell size of BaZrO3 was 4.1982A. Calculation by CASTEP procedure gives that the indirected band gap is 3.49eV, the O2p atom contribute the top electrons of valence band, and the Zr4d atom contribute the bottom electrons of conduction band.A series of BaZr1-xYxO3- ?(0?x?0.3) were prepared via sintering at 1200? for 5h, pressing into sheets, and then sintering at 1500? for 48h by a high temperature solid state reaction. XRD analysis shows that the maximum content of Y is up to 24mol%. With the increasement in doping concentration of Y, the conductivity of sample increases (x? 0.2). However, the conductivity of samples with a Y-doped content of 22mol% or 24mol% is lower than that of samples with a Y-doped content of 20mol%. Generally, Y-doped BaZrO3 would produce defects (Y2O3?BaZrO32YZr+Vo+3Oo). Emission spectroscopy and thermolumine-scence spectra indicate that two non-equivalent oxygen vacancies (VO) formed, which are beneficial to the proton conductivity. However, Y-doped BaZrO3 lattice generates a new center with negative charge (YZr), which is able to capture the proton in crystal and thus reduce the concentration of protons (YZr+H?(YZr·H)x). With the increasement of Y-content, the YZr defect traps shallow, the proton-capture capabilities are thus reduced, and the the release ability of trapped protons (YZr·H)×??YZr+H) are correspondingly increased. Therefore, the conduct-ivity may be increased.Besides, BaZr0.8Y0.2O3-?5 were prepared with different fluxes by a high-temperature solid-phase reaction. A single-phase powder, with the greatest lattice parameters and a high degree of crystallinity, was obtained by sintering at 950? for 5h using LiOH as flux. In conclusion, all refluxes applied could effectively improve the density of the ceramic body:LiOH>LiCl>NaCl>NaOH>BZY20. Experiments show that incorporation of LiOH and NaOH could obviously improve the proton conductivity, while LiCl and NaCl could slightly decrease the proton conductivity. The sample with LiOH or NaOH as flux has a lower peak T1 in thermoluminescence spectrum, a lower peak P1 in emission spectra, and a lower defect concentration of YZr, which is beneficial to reduce proton-capture abilities; The T1 peak of thermoluminescence shifts to a lower temperature, and the defect trap of YZr shallows, resulting in the proton-capture ability decreasement. Therefore, the conductivity of samples doped with LiOH or NaOH are improved obviously. Comparatively, the emission spectrum of samples doped with LiCl or NaCl did not significantly change, indicating that the incorporation of flux does not make the concentration of defect YZr decrease; However, the peak T1 of thermoluminescence moved to a higher temperature, and the defect YZr trap was deepened, giving a higher proton-capture ability. Therefore, the proton conductivity doped with LiCl and NaCl decrease slightlyUsing LiOH or NaOH as flux, a Y-doped BaZrO3 based material with a good conductivity was prepared at a lower temperature for a shorter sintering time. The defect types and proton conductivity mechanism of BaZr1-xYxO3-? materials were thoroughly studied by emission spectroscopy (PL) and thermoluminescence (TL). |
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