铁酸盐复合氧化物（MFe₂O₄）系列气敏材料的制备及新型气体传感器的研究

【作者】 杨留方；

【导师】 赵怀志；

【作者基本信息】 昆明理工大学 ， 材料学， 2005， 博士

【摘要】 本论文系统地研究了铁酸盐复合氧化物（MFe₂O₄）新型气敏材料。采用反滴定化学共沉淀法制备出了NiFe₂O₄、MgFe₂O₄、CdFe₂O₄和Zn_0.5Ni_0.5Fe₂O₄纳米粉末,对材料制备方法和工艺、材料结构的表征、材料合成、反应动力学、材料的气敏特性、气敏机理等作了较系统的研究;对新型组合结构气体传感器的原理进行了研究,提出了材料选择原则,制作出了几种组合结构气体传感器。 1、NiFe₂O₄、MgFe₂O₄、CdFe₂O₄和Zn_0.5Ni_0.5Fe₂O₄纳米材料的制备工艺、结构表征及性能测试。 （1） 采用反滴定化学共沉淀法制备出了NiFe₂O₄、MgFe₂O₄、CdFe₂O₄和Zn_0.5Ni_0.5Fe₂O₄纳米材料,获得了上述材料的最佳制备工艺。 （2） 通过X射线衍射谱测定了粉末的晶粒粒径。在不同热处理温度（350℃～700℃）下获得的NiFe₂O₄晶粒粒径为9～39nm;在500℃～700℃热处理温度下获得的MgFe₂O₄晶粒粒径为14～19nm;在600℃热处理温度下获得的CdFe₂O₄晶粒粒径为80nm;在600℃热处理温度下获得的Zn_0.5Ni_0.5Fe₂O₄的晶粒粒径为50nm。用透射电子显微镜（TEM）测量得到的二次粒子的颗粒直径为100nm左右。 （3） 采用室温固相合成方法合成了CdFe₂O₄粉末,与反滴定化学共沉淀法进行了比较。结果表明,反滴定化学共沉淀法,在热处理温度为700℃时可获得单相的CdFe₂O₄;而室温固相合成法,在该热处理温度下获得的产物不是单相的CdFe₂O₄,而是CdO、Fe₂O₃及CdFe₂O₄的混合物,且合成前驱物时,反应激烈,反应热难以控制。 （4） 研究了NiFe₂O₄、MgFe₂O₄的晶粒生长动力学。其生长均遵从Arrhenius方程,2LnD与1/T满足单一线性关系。通过计算,得出NiFe₂O₄在350～700℃之间晶粒生长活化能为42.00 kJ/mol;MgFe₂O₄材料在500～700℃范围内晶粒生长的活化能为17.58kJ/mol。 （5） 对NiFe₂O₄、MgFe₂O₄、CdFe₂O₄和Zn_0.5Ni_0.5Fe₂O₄纳米粉末的气敏特性进行了测量。通过实验发现,在一定的工作温度下,NiFe₂O₄纳米超细粉体对甲苯（C₆H₅CH₃）敏感性高,MgFe₂O₄对丙酮（CH₃COCH₃）敏感性高,更多还原

【Abstract】 Gas sensitive materials of spinel type ferrite （MFe₂O₄） composite oxides were studied systematically in the thesis. NiFe₂O₄, MgFe₂O₄, CdFe₂O₄ and Zn₀.5Ni₀.5Fe₂O₄ powders were prepared by inverse titration chemical co-precipitation. The method and the technology of preparation, the structures, gas sensitive properties and gas sensitive mechanism of the materials were researched, and reaction kinetics of NiFe₂O₄ powders and MgFe₂O₄ powders were discussed. Principles of new combined structure gas sensors and choosing materials were also studied. The combined structure gas sensors based on the powders were prepared. The results are as follows:1. The preparation techniques, structures and gas sensing properties of NiFe₂O₄, MgFe₂O₄, CdFe₂O₄ and Zn₀.5Ni₀.5Fe₂O₄ nano-powders.（1） By applying inverse titration chemical co-precipitation to obtain NiFe₂O₄, MgFe₂O₄, CdFe₂O₄ and Zn₀.5Ni₀.5Fe₂O₄ nano-powders, the best techniques of above materials were acquired.（2） The sizes of NiFe₂O₄, MgFe₂O₄, CdFe₂O₄ and Zn₀.5Ni₀.5Fe₂O₄ nano-powders were analyzed by means of powder XRD. The diameter of NiFe₂O₄ powders sintered at 350⁷00℃ is about 9-39 nm, MgFe₂O₄ powders at 500⁷00℃ about 14-99 nm, CdFe₂O₄ powders at 700 ℃ about 80 nm, Zn₀.5Ni₀.5Fe₂O₄ powders at 600℃ about 50 nm. The size of the powders through TEM is about 100 nm.（3） CdFe₂O₄ powders were synthesized by solid reaction at room temperature, comparing with inverse titration chemical co-precipitation. The results exhibited that pure CdFe₂O₄ powders sintered at 700℃ were obtained by inverse titration chemical co-precipitation, but CdFe₂O₄ powders were complex oxides with CdO and Fe₂O₄, and the reaction was so tense that the reaction energy was not controlled.（4） Reaction kinetics of NiFe₂O₄ powders and MgFe₂O₄ powders were studied. The crystallite sizes increase with the increase of calcining temperature, whichfollows Arrhenius equation. The changes of 2LnD with 1/T for the NiFe2O4 materials and MgFe2O4 materials are approximately linear , and the activation energy of the NiFe2O4 materials sintered at 350- 700°C is 42.00 kJ/mol. The activation energy of the MgFe2O4 materials sintered at 500⁷00°C is 17.58 kJ/mol.（5） The gas sensing properties of NiFe2C>4, MgFe2O4, CdFe2C>4 and Zno.5Nio.5Fe204 powders were also studied. It was discovered that sensors based on NiFe2C>4 powders exhibited higher sensitivity and better selectivity to toluene （C6H5CH3） at 300°C; that the sensors based on MgFe2C>4 powders higher sensitivity and better selectivity to CH3COCH3; that the sensors based on CdFe2O4 powders higher sensitivity and better selectivity to ethanol （C2H5OH）; that the sensors based on Zn0.5Nio.5Fe204 powders higher sensitivity and better selectivity to ethanol （C2H5OH） and acetone （CH3COCH3）. The work was reported for the first time. 2. Gas sensitive mechanism of spinel type ferrite （MFe2O4） materials.（1） The reversible adsorption and the irreversible adsorption of gases for NiFe2O4powders were examined, comparing with the sensitive properties of sensors based on NiFe2O4 powders for gases at- different operating temperature. It is found that the total adsorption bears a liner relation to the sensitivity for gases and vise versa.（2） According to the MFe2O4 gas-sensing materials which deviated normal chemical components, to adsorption properties and surface principle, the gas-sensing mechanism of n-type and p-type MFe2O4 materials were put forward. The work was not reported.3 N+p and n+n structure semiconductor gas sensors based on the compensation-multiplication and compensation-feedback principle were studied in advance. The sensors are composed of two sensitive body A and B. The sensing properties of the structure semiconductor gas sensors have been improved when the sensitive body A and B satisfied certain conditions.4 The combined structure semiconductor gas sensors based on thecompensation-feedback and compensation-multiplication principle by choosing sensitive body A and B were designed, and its sensing properties were studied.（1） The n+p combined structure gas sensor based on the compensation-multiplication principle for ozone （O3） was obtained. hr^C^ and Pt doped p-type NiFe2O4 material used as sensitive body B, Nb2O5 doped n-type ZnO material used as sensitive body A which has better sensitivity for ozone compared with doping WO3. The gas sensor showed higher sensitivity and better selectivity to ozone gas.（2） The n+p combined structure gas sensor for ethanol （C2H5OH） was researched in this thesis. In2O3 and Pt doped n-type CdFe2O4 material used as sensitive body A, and sensitive body B is p-type C02O3 complex oxides. The experimental results exhibited that the sensor displayed higher sensitivity and selectivity, better thermal stability for ethanol.（3） The n+n combined structure gas sensor based on the compensation-feedback principle for acetone （CH3COCH3） was reported in this thesis. ZnO and ZrC>2 doped n-type MgFe2C>4 material used as sensitive body A, Nb2Os, Sb2C>3 and Pt doped n-type SnO2 material used as sensitive body B. The experimental results revealed that the sensor had higher selectivity for acetone.更多还原