Wet process-prepared thick films of WO3 for NO2 sensing
Wet process-prepared thick films of WO3 for NO2 sensing
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DOI：
10.1016/s0925-4005(03)00439-8
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发表时间：
2003-10
影响因子：
8.4
通讯作者：
Y. Choi;G. Sakai;K. Shimanoe;N. Miura;N. Yamazoe
中科院分区：
文献类型：
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作者：
Y. Choi;G. Sakai;K. Shimanoe;N. Miura;N. Yamazoe
以Na_2WO_4为原料，采用离子交换法制备WO_3·2H_2O水溶胶，并结合后处理（超声波和/或离心），得到了不同形态和取向的WO_3·2H_2O凝胶。水相WO 3·H2O和三氧化钨（WO 3）的脱水相很好地继承了凝胶的形貌，从而可以通过湿法工艺控制WO 3的形貌。由凝胶制成并在300°C下煅烧的WO 3厚膜器件被发现对空气中的NO2显示出非常不同的传感器响应，这取决于WO 3的形态。也就是说，通过超声处理较长时间（5 h）获得的欠发达的小片层WO 3在200°C下给出了最灵敏的器件，其可以响应低至10 ppb的NO2，而通过离心处理较长时间（10 h）获得的发达的薄片层WO 3在300°C下给出了最灵敏的器件。为了了解传感器响应对WO 3形貌的依赖性，还采用了其他几种方法制备WO 3。结果表明，在300°C时，所有的传感器响应数据都与WO 3片层厚度或WO 3晶粒直径有很好的相关性，而在200°C时，这种相关性变得不那么确定。
Preparation of an aqueous sol of WO3·2H2O starting from Na2WO4through an ion-exchange method, coupled with post-treatments (ultrasonic and/or centrifugal), was found to give WO3·2H2O gels which differed in morphology and preferred orientation depending on the kinds and conditions of the post-treatments. The morphology of the gels was well inherited topotaxically by the dehydrated phases of WO3·H2O and tungsten trioxide (WO3), allowing to control the morphology of WO3by the wet processing. The WO3thick film devices, fabricated from the gels and calcined at 300°C, were found to show very different sensor responses to NO2in air depending on the morphology of WO3. That is, poorly developed, small lamellas of WO3obtained by the ultrasonic treatment for a prolonged time (5h) gave the most sensitive device at 200°C, which could respond to as low as 10ppb NO2, while well developed, thin lamellas of WO3obtained by the centrifugal treatment for a prolonged time (10h) gave the most sensitive one at 300°C. In order to understand the dependence of sensor response on the morphology of WO3, several other methods were also adopted for preparing WO3. It was found that all of the sensor response data collected at 300°C could be related fairly well with the thickness of WO3lamellas or the diameter of WO3grains, whereas such a relationship became less certain at 200°C.