| In recent years, the rapid development of semiconductor integrated circuit manufacturing industry leads to the high value-added electronic sputtering target material has a broad market. Dense ceramic material which is a tin oxide has a direct band gap of wide band gap semiconductor material, and it has good chemical, mechanical, thermal stability, high rate of migration characteristics. It is a potential substitute for ITO material. SnO2 thin film as an excellent functional material, it has broad application prospects in the transparent conductive film and the field of chemical gas sensors. However, due to the poor sinterability of SnO2, the SnO2 is difficult to densify, so there are very few reports on the SnO2 ceramic target, and the mechanism of the densification of SnO2 ceramics and conductive mechanism of divergent views are still controversial.This paper firstly prepared pure SnO2 ceramic target, using spark plasma sintering (SPS), by analyzing the process parameters such as sintering temperature, pressure, holding time and heating rate. the sintering process of the 1000℃-40MPa-3min-200℃/min, which the target relative density (of) reaches 96.6%. Whereas, it is impossible to fabricate the pure and high densification SnO2 ceramic target.The results of pure densification of SnO2 ceramic target research show that the mechanisms of densification of pure SnO2 ceramic target by SPS were:SPS sintering process produces local high temperature, causing the abnormal growth of grains, and producing a high vapor pressure difference, mass transfer through evaporation condensation method transfer; Second, the Sn2+ is replaced with Sn4+ in the process of SPS,SPS sintering processes of Sn2+ to replace Sn4+, generating oxygen vacancies promote the densification of SnO2. Isostatic cool pressing-sintering is mainly evaporation - condensation of mass transfer.Secondly, ATO is prepared by mechanical mixing Sb2O3 doped SnO2 composite powder, and it is analyzed the effect of sintering temperature and Sb2O3 doping on the density. The results show that temperature between 800℃-1000℃can get high density of ATO (97.56SnO2-2.44Sb2O3) ceramic target. The relative density of ceramic is 98.2% by sintering ATO (99SnO2-1Sb2O3) in the 1000℃-40Mpa-200℃/ min-3min. Some amount of Sb2O3 help to promote moderate temperature of dense SnO2.The densification of ATO ceramic sample by SPS is the result of interaction of the following four main mechanisms:First, in the SPS sintering process, abnormal grain growth is generated by the local high temperature and the mass transfer is evaporation-condensation; Second, Sn4+ replaced by Sn2+ generated the oxygen space promote the densification of SnO2; third, densification is mainly through the Sb3+ solution to the SnO2 lattice oxygen vacancies to promote densification. Sb3+ and Sn4+ price difference, Sb+ (0.076) replaced with Sn4+, makes the neighboring oxygen atoms form a large number of oxygen vacancies, and promote crystal growth to densify SnO2 ceramics. At last, Sb5+ as a donor substituted for Sn4+ and Sn2+ of SnO2, and Sb3+ replace Sn2+, the combination of obstruction and growth of SnO2 particles is not conducive to the densification of SnO2.Electrical properties of ceramics prepared by SPS ATO, when Sb doping concentration is low, such as Sb doping was 0.1%, Sb5+ replace the main Sn4+ donor doping; With the increase of Sb doping, such as the amount of Sb doping was 2.44%, Sb5+ /Sb3+ increase in carrier concentration mainly by Sb5+ / Sb3+ ratio is determined mainly by Sb5+ donor doping, abnormal grain growth reduces the effective grain boundary area; when Sb doping increased to a certain degree, Sb5+/ Sb3+ ratio declines and the conductivity mainly Sb5+ the donor doping and oxygen vacancies to decide.To improve the performance of ceramic targets, and it is finally prepared by wet doped ZnO SnO2, Sb2O3 doped SnO2, ZnO-Sb2O3 doped SnO2 composite powder.When the SPS sintering process is 1000℃-40MPa-3min-200℃/min and ZnO doped lmol%, the availability of SnO2-ZnO ceramic target maximum density is 6.98 g·cm-3, and the relative density of the great value is 99.8%; SnO2-1Sb2O3 ceramic target density and relative density reached the maximum 6.88 g·cm-3 and 98.3% respectively; SnO2-lZnO-1Sb2O3 ceramic target density and relative density reached the maximum 6.96 g·cm-3 and 99.2% respectively.The room-temperature resistivity of Sb2O3 doped ATO ceramics decreases rapidly with the sintering temperature decreasing, but increasing the temperature, change is not obvious. At 900℃, the resistance rate is 6.63×10-2 (?)·cm, and at 950℃, the minimum value reaches 9.1 x 10-3 (?)·cm. When the sintering temperature is 1000℃, with increasing the content of Sb2O3 doped SnO2-based ceramics, the room temperature resistance decreases rapidly, but with further increase in doping Sb2O3, resistivity at room temperature do not change significantly, when the Sb2O3 doping content is 0.5mol%, SnO2 samples reached the minimum room temperature resistivity of 2.3×10-2(?)·cm. |
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