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利用二氯化钯(PdCl_2)溶液浸渍法,研究了二氧化钛(TiO_2)厚膜钯(Pd)原子表层扩散对氧气响应特性的影响。扫描电子显微镜显示:Pd扩散后厚膜表面均匀分布着纳米级Pd晶粒。利用Kroger-Vink方程分析了不同扩散时间下对应的lnR-lnpo_2曲线,针对不同斜率的曲线,用缺陷方程分析了Pd元素的分布状态。样品响应特性的伏安法测试结果显示:820℃,2h扩散的敏感膜具有理想灵敏度和响应时间。研究结果表明:Pd元素在敏感膜表面形成了纳米级Pd晶粒,并在TiO_2厚膜表层中存在着少量的钯间隙原子(Pd_i)及替位钯离子(Pd~(2+))。合理的扩散温度和扩散时间,可获得表层Pd氧化量最少、扩散浓度合适的敏感膜,进而获得效果理想的厚膜氧敏材料。
The influence of Pd (superscript 2 +) surface diffusion on the response to oxygen was investigated by using PdCl2 solution impregnation method. Scanning electron microscope (SEM) shows that the nano-scale Pd grains are uniformly distributed on the surface of the thick film after Pd diffusion. The corresponding lnR-lnpo_2 curves at different diffusion times were analyzed by Kroger-Vink equation. The distribution of Pd elements was analyzed by the defect equation for different slope curves. Voltammetric test results of the response characteristics of the samples show that the sensitive films diffused at 820 ℃ for 2h have the ideal sensitivity and response time. The results show that the Pd element forms nano-sized Pd grains on the surface of the sensitive film, and there are a small amount of palladium interstitial atoms (Pd_i) and substitutional palladium ions (Pd 2+) in the surface of the TiO_2 thick film. Reasonable diffusion temperature and diffusion time, can be obtained on the surface of the Pd oxide at least, the diffusion concentration of the appropriate sensitive film, and then get the desired effect thick film oxygen sensitive materials.