| In2009, our group first reported that Tb4O7-based ceramics exhibit apparent varistor behavior and anti-aging ability. This novel nonlinear resistor system is helpful for further understanding the problems that remain unclear in addition to satisfying the need for better electrical properties. However, the use of terbium dioxide ceramics is limited by low densification during the sintering process. The bonding energy of surface oxygen to terbium is weak due to the low symmetry structure, and the oxygen ions can readily flee from the original sites Cu2O has a high symmetry structure with strong bond energy. There is a possibility that Cu can substitute for Tb ions in the lattice and thereby improve the densification process. The goal of the existent job is to research the influence of CuO on the microstructure and electrical properties of Tb4O7-based ohmic resistance. Results include a reduction in the sintering temperature to1100°, a grain size of4.2μm, and a density of96.2%, which are larger than the values in previous investigation for TB4O7ceramics (0.4μ m and70.0%). Among the sintered ceramics, the sample doped with10.0wt%Tb4O7showed the maximum nonlinear coefficient α=43.5, which is obviously greater than α=3.03of the pure sample. Doping with CuO also exhibited nonlinearity α=2.14even at1123K. Al2O3doped TO4O7is also researched, while Al2O3can’t improve the density and nonlinearity. So, CuO is treated as dopant in this article.To maintain the electrically neutral, the negative allegation on the grain boundary is balanced on both sides by the electron depleted space-charge layers in the adjacent grains, which formed the Schottky barriers. Such barriers in Tb4O7can hinder the movement of electrons. For purpose of verifying the correctness of the model, the samples were sintering in Ar、O2、 Ar with O2. It demonstrated that the samples sintering in argon gas had poor density, small grain size but an excellent nonlinear. Li tong ye got the same result of Pr6O11sintering in argon gas. He considered this phenomenon can’t be explained by the grain boundary surface features of Schottky barriers. It is similar to the nonlinear mechanism of ZnO ceramic which is caused by the high resistance tier in crystal boundary. Combining with our experimental results, we agree with his view on the samples sintering in argon gas. Due to the poor density and small grain, the nonlinear is also by Microstructure. Furthermore, we find O2can improve the samples’density which can promote the growth of crystal size. It also makes the nonlinearity much larger. With the CuO adding, the second phase gathered in the grain boundary, which hindered the material transportation and increased energy of Schottky barriers. As a consequence, the grain size, density decreased and nonlinear increased.With previous studies, we found that CuO-TD4O7had excellent microstructure and electrical performance. With the purpose of getting more excellent performance, we doped WO3and Al2O3in CuO-Tb4O7ceramics. Through the experimental results, we found that both WO3and Al2O3can’t obviously improve the electrical performance of CuO-Tb4O7ceramics. To some extent, they decrease the performance of CuO-Tb4O7ceramics. It can be explained by the influence of other phases which gathered in the grain boundary and hindered the material transportation. The relative molecular mass of Tb4O7is747.7, which is much larger than other metal oxide. So, we Choose quality score (wt%) as the doping standard. |
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