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Nano- materials research Cr_2O_3 based gas

Author: QiXiaoJuan
Tutor: HuoLiHua
School: Heilongjiang University
Course: Inorganic Chemistry
Keywords: Cr2O3 nanopowders soft chemistry synthesis gas sensitivity RF sputtering
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 68
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Abstract


The oxide semiconductor gas sensors with simple structure, low cost and high sensitivity have been widely applied. It is still necessary for the sensors to improve their stability and selectivity. It is urgent to develop new gas-sensing materials. Therefore, the development of Cr2O3 nano-material as a new candidate for the gas-sensing material is of great significance.In this paper, precipitation, hydrothermal synthesis and citrate methods were used to synthesize Cr2O3 nanopowders, and co-precipitation method was used to synthesize Cr2-xMxO3（x=0.1-0.5）（M=Fe、Sn、Ni）nanopowders. The structures of materials have been characterized by XRD, SEM, BET and XPS techniques. Their thick film-type gas sensors were fabricated and their gas sensitivities were measured to acetone, 1-propanol, ethanol, methanol, benzene and toluene. The results show that Cr2O3 prepared by precipitation method with nano-powders has better gas sensitivities. The sensitivity of the powders sintered at 450 oC is better than that of the material sintered at 350 oC. The thick-film sensor has high gas sensitivities to 1-propanol, acetone, ethanol and methanol gases at the best heating voltage of 4 V. It could detect 1-propanol, acetone and ethanol as low as 10μL·L-1 and exhibits good humidity-resistivity. After Fe, Sn and Ni elements were doped, the electrical conductivity and gas sensitivities of the materials were improved to some extent and the working temperature was also decreased a little. Among Cr2-xMxO3（x=0.1-0.5） （M=Fe、Sn、Ni） materials, Cr1.5Ni0.5O3 has the highest gas sensitivity to 1-propanol, and decrease in the order of acetone, ethanol and methanol. It could detect 5μL·L-1 of 1-propanol, acetone and ethanol. The response and recovery times of Cr1.5Ni0.5O3 were significantly shortened than that of pure Cr2O3. The Cr1.5Ni0.5O3 nanomaterial still shows better humidity-resistivity.Cr1.5Ni0.5O3 thin film was prepared by the RF sputtering method and heated at 700oC for 5 h. The XPS analysis indicated that the composition and surface state of Cr1.5Ni0.5O3 thin film are basically similar to those of the powder. Comparing with the Cr1.5Ni0.5O3 thick film, the response and recovery capabilities of Cr1.5Ni0.5O3 thin film was increased, but the gas sensitivity was a little decreased.

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