Study On Preparation And Sintering Properties Of La₂O₃,Pr₂O₃ Doped SnO₂ Electrode Ceramics

Tin dioxide electrode with excellent electrically-conductive property in high temperature and good corrosion resistance to molten glass and no pollution to environment has extensive application in all kinds of glass electric-melting, especially it could be used to melt top-grade glass such as lead glass and optical glass and so on. Due to pure tin dioxide belongs to material which is not electric and hard to sinter, the chief problem needs to resolve of preparing electric tin dioxide ceramic is how to improve electrical properties and sintering properties of tin dioxide. However, nowadays the studies about tin dioxide are mainly focused on gas sensitivity ceramic, capacitor ceramic and electric films of tin dioxide, the studies about tin dioxide electrode are less, domestic electrodes have low quality and the high quality tin dioxide electrodes are still depended on import, therefore, it is urgent to study the domestic tin dioxide with excellent electrical properties and sintering properties.In this paper, preparation of powder, forming process and sintering process were studied, a new technics about preparation of SnO₂ electrodes was established, the influence of the different additives and their contents were discussed. According to diversified test results, the influence mechanism of every additive and its content and sintering process were also analyzed, a new type SnO₂ electrode which both had better resistivity and bulk density than domestic electrode was prepared successfully.Considering nano-scale powder had a good improvement on the sintering of the electrodes, and pure nano-SnO₂ raw material was prepared by co-precipitation method could reduce impurity brought by industrial raw material. Compound doped nano-SnO₂ powders prepared by co-precipitation method were studied in chapter two. SnO₂ powders singly doped by La and mixed doped by La, Sb, Ce and Zn were prepared, keeping the same pH by co-drop mode. The test results of XRD and TEM showed SnO₂ had a rutile structure of the square crystal system; a good growth grain and SnO₂ powder presented like a ball and the grain size was from 10 to 25 nanometers; additive did not change SnO₂ crystal type and the increase of La additive could inhibit the crystallization of SnO₂.Powders were prepared and next were powders getting wet, forming under normal pressure, drying samples and finally compound doped SnO₂ electrodes were obtained. In chapter three, after studying forming pressure and sintering temperature in the process, I found when the forming pressure was 30Mpa and sintering temperature was between 1300 and 1400℃, SnO₂ electrode had a lowest resistivity. Through the influence of the additives, I also found La₂O₃, Sb₂O₃ doped had a remarkable effect on the electrics performance and discussed the doped theory, the resistivity of electrode which had the best doped contents involved 1.5wt% La₂O₃ and 1.0wt% Sb₂O₃ is 98Ω·cm, it was lower than 185Ω·cm of the domestic electrode.La₂O₃ doped had a nice improvement on the electrics performance of the SnO₂ electrodes, for researching the effects of the La₂O₃ doped content and sintering process on the densification of the electrodes, the best sintering project and the highest sintering temperature were investigated, the densification theory also was discussed in chapter four, the results showed La₂O₃ doped had a big improvement on the densification of the SnO₂ electrodes. With the increase of La₂O₃ content, the bulk density of samples increased at the beginning then decreased. The best bulk density of sample doping 1.5wt% La₂O₃ was up to 6.514g·cm^-3, it was better than 6.4 g·cm^-3 of the domestic electrode.SnO₂ electrodes research hardly involved doped chemical Pr at the present time, for studying the effect of the Pr doped on the electrodes, the effects of the Pr₂O₃ doped content on the properties of the SnO₂ electrodes in the chapter five. The results showed Pr₂O₃ doped had an unconspicuous improvement on the properties of the SnO₂ electrodes. The reason mainly was doping Pr₂O₃ enriched other elements (Zn, La and Sb) on the SnO₂ crystal surfaces, and destroyed the integrality and regular arrangement SnO₂ crystal, lead to sloppy and loose electrodes at the same time made resistivity increase fast.