| With the development of modern science and technology progress, the requirement of multi-function devices has become more and more urgent. And multiferroic materials, which combine the properties of ferromagnetism, ferroelectricity, or ferroeleasticity, have attracted a lot of attention of scientists. The magnetoelectric coupling effect in multiferroic materials can make the high speed reading and writing in computer come true. In addition, the study of multiferroic materials across the disciplines of condensed matter physics and material science, which brings out many questions and challenges, is very significative to the theoretical physics.In various known multiferroic materials, the layered perovskite Bi5Ti3FeO15 ceramics has many superior properties, such as fatigue resistance, high Curie temperature, small leakage current and good stability. As a result, the Bi5Ti3FeO15 deserves wide attention. But the room temperature ferromagnetism is very weak, which seriously hindered the promising application prospect of Bi5Ti3FeO15 materials.There have been the reports on the magnetoelectric properties of the Bi5Ti3FeO15 ceramics which were doped the magnetic ions to the B set in the experiments. But the results of the experiments are not satisfactory.In this experiment, the Bi5Ti3FeO15 ceramics has been made by solid state reaction, and the Cr3+?Ni3+ was used to doping to the B set of the Bi5Ti3FeO15 ceramics. The main content includes the following three aspects:1?The Bi5Ti3FeO15 ceramic samples, Bi5Ti3Fe1-xCrxO15(x=0.1, 0.2, 0.5, 0.7)ceramic samples and Bi5Ti3Fe1-xNixO15(x=0.1, 0.2, 0.3, 0.4, 0.5, 0.7)ceramic samples were prepared by solid state reacting at the sintering temperature 700??800?and 900?.The rapid quenching method used here can effectively restrain the volatilization of Bi elements and reduce the structural defects and oxygen vacancy in the samples.2 ? The XRD test and the SEM test were made on our samples, Bi5Ti3Fe1-xCrxO15(x=0.1, 0.2, 0.5, 0.7)ceramic samples and Bi5Ti3Fe1-xNixO15(x=0.1, 0.2, 0.3, 0.4, 0.5, 0.7)ceramic samples. XRD test results show that the Bi5Ti3FeO15 ceramic samples are four layers perovskite structure in the proper sintering temperature 700?~800?. Cr ions doping has not significant effect on the sintering temperature and grain structure on Bi5Ti3FeO15 ceramics. However the Ni doping has great influence on the sintering temperature of the Bi5Ti3FeO15 ceramics. As the Ni content x increasing and the sintering temperature rising, the four layers perovskite structure of the samples can only formed in 900? and x?0.05. The SEM test also shows that the grain size decreases with the Ni content x increasing in the sintering temperature 900?3?The room temperature ferromagnetisms were measured in our samples, the Bi5Ti3FeO15 ceramic samples, Bi5Ti3Fe1-xCrxO15(x=0.1~ 0.7)ceramic samples and Bi5Ti3Fe1-xNixO15(x=0.1~ 0.7)ceramic samples. The remanent magnetization 2Mr and the coercive field 2Hc were also analysed on the simples.The measured result is that the Bi5Ti3FeO15 ceramic sample, made by rapid quenching method, shows the same remanent magnetization with the sample made by substep sintering method in the references. And the coercive field 2Hc are larger. Although the Cr doped samples sintered in 900? all show the paramagnetic characteristics, the samples sintered in 750? have obvious hysteresis loops with 2Mr~7.56*10-3 em?/g and 2Hc~4034 Oe,which are the difference with the result in the references. The room temperature magnetism of Ni doped samples is much improved compared to Bi5Ti3FeO15 ceramics. The x=0.3 samples shows the best magnetism with 2Mr~0.19198 em?/g and 2Hc~824.33 Oe. The room temperature ferromagnetism of the Bi5Ti3FeO15 ceramic sample is the best at present. |
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