| Pr3+-doped C12A7 powders were fabricated by the self-propagation synthesis methods.X-ray diffraction(XRD), excitation spectra and emission spectra were conducted to investigate the microstructure of the powders. The XRD result showed that polycrystalline12 Ca O·7Al2O3(C12A7) powders with nanocaged stucture were obtained. The characteristic emission peak of Pr3+were observed in the excitation spectra and emission spectra. These results suggested that Pr3+ had been doped into the host without destroying the structure of the lattice.To obtain encaged H- and OH-, we first annealed the as-prepared powders in hydrogen ambient(20%H2/80%N2) at the calcining time of 3 and 6 hours, respectively, then the samples were carefully grinded. The emission spetrum result shows that the ratio of blue to red luminesecnt intensity is gradually increased with increasing the annealing time. This mainly is due to the reaction of O2-(cage)+H2(atmosphere)? OH-(cage)+H-(cage) happened in H2 ambient and the lattice local environment arround Pr3+was changed. With increasing the annealing time, the number of high-energy vibration group( encaged OH- ions) was increased.It will accelerate the non-radiation transition rate of3P0'1D2. The fluorescent decay measurement showed that the lifetime of 3P0 level gradually decrease with increasing the annealing time which is agreement with the PL result.The conductivity of C12A7:x%Pr3+ was measured by adoping AC impedance meth od. It can be observed that, with increasing the doped Pr3+concentration,the conductiv ity of bulk and grain boundary increased. It can be explained by the fact that accordi ng to the principle of charge compensation,with the increasing of the doped with rare earth Pr3+ concentration, will induce the cage produce more of the O2- ions, when at t he temperature of 1350°C and dry oxygen O2 atmosphere heat treatment, will generate more O- ions, so the conductivity will increases. By changing the kinds of doped with rare earth ions as electrolyte,the electrical conductivity of grain will be increase,this may be due to that When doped with rare earth ions Sm3+ will cause larger cage distortion,This will provide wider access for the transmission for the O2-ions,so the electrical conductivity of grain will increase, At the same time findingthe same phenom enon on the doped mentioned above, on the heating and cooling process of Arrhenius curves, at the same temperature,the Arrhenius curve of grain is not coincidence and the Arrhenius curve of grain boundary is also not coincidence, this shows that :the reaction of is constantly moving in the test temperature range.That is to say,In each temperature preservation,the reaction is constantly shifting.The test results of each temp erature preservation show that:when the temperature is large than 650°C(650°C to 800°C),The reversible reaction of is constantly moving to the right with the temperature preservation time increasing.When temperature is less than 650°C(550°C to 600°C), t he above reaction is constantly moving to the left with the time increasing. At the sa me time,The test results of temperature preservation show that:the theory equilibrium c oncentration is difficult to achieve simply through the temperature preservation for a l ong time,and the actual balance concentration at a certain temperature is not only affe cted by the theory equilibrium concentration,but also significantly affected by the histo rical process.This is very important for the practical application for the O2-、O2-、Oion based the reaction O2-(cage)+O2(atmosphere)?O-(cage) + O2-(cage). |
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