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Gas sensing properties of perovskite -type materials

Author: YangFen
Tutor: ZhangPengXiang
School: Kunming University of Science and Technology
Course: Materials Science
Keywords: gas sensitivity perovskite structure La1-xSrxCoO3 Pulse Laser Deposition
CLC: TB321
Type: Master's thesis
Year: 2004
Downloads: 190
Quote: 2
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Abstract


With the development of society and the improvement of people’s living conditions, gas-sensors have been used more and more widely. Semiconductor-typed gas sensor is one kind of most widely used gas sensors. Muti-components oxides have been thought as one of promising materials used in gas sensors.Precursor was synthesized by co-precipitation method in this paper, then it was heated by two stage technology so La0.5Sr1.5MnO4, La0.7 (Ca0.53Sr0.47Mn) 0.3, La0.33Ca0.67MnO La0.5Sr0.5CoO can be produced. XRD Patterns have proved that these Muti-components oxides show single-phase structure and no other phases appeared. Synthesized materials showed good size distribution according to SEM and particle size analysis results. The synthesis technology used here combined the advantages of both sol-gel method and solid heating.The synthesized La1-xSrxCoO3 materials were made into gas sensor film according to PLD method and gas sensor characters were investigated. The test results showed that LaCoO3 and La0.5Sr0.5CoO3 were sensitive to H2 and C2H5OH, but the CH4 sensitivity is near to zero. The H2 sensitivity of these two film samples raised with temperature, and this tendency pricked up when the temperature was over 200C. The H2 sensitivity of La0.5Sr0.5CoO3 was higher than which of LaCoO3. The C2H5OH sensitivity of these two samples raised with temperature till 200C then began to drop concussively. The gas sensitivity of the two samples increases with the ethanol concentration because of the higher resistance in higher concentration.Although the initial gas sensitivity of La0.5Sr0.5CoO3 is higher than LaCoO3, the later is more stable. The H2 sensitivity of LaCoO3 change slightly in storage while the H2 sensitivity of La0.5Sr0.5CoO3 drop greatly. The reason is the formation of oxygen-deficient because of the partial substitute of Sr to La, which stimulates the lattice oxygen diffusing from inner to the surface. This caused the destruction of perovskite structure, which increased the resistance of the samples. So the doped sample has higher gas sensitivity but worse stability.In addition, LaCaMnO, LaSrMnO, LaCaSrMnO also have been investigated, however, the sensitivity does not exist.

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