乙醇作为一种典型的挥发性有机化合物，在制药、涂料与能源等领域被广泛用作溶剂和燃料。然而，其具有易燃易爆的特性且对人体健康存在危害，使得对其浓度的快速检测显得尤为重要。SnO₂是一种n型半导体材料，因宽禁带（Eg=3.6 eV）和低成本等优势，广泛应用于气体传感器领域，然而单一的SnO₂气体传感器存在着气体响应差等问题。为提升气敏性能，本文引入了p型半导体Bi₂O₃，与SnO₂复合形成pn异质结结构，该复合结构能够提升对乙醇气体的响应，为实现对乙醇的可靠检测提供了新思路。

本文制备了SnO₂@Bi₂O₃异质结气体传感器，通过正交实验优化制备了SnO₂@Bi₂O₃异质结的参数，探究SnO₂@Bi₂O₃异质结气体传感器的气敏性能。同时，探讨了不同金属元素掺杂对SnO₂@Bi₂O₃异质结气体传感器气敏性能的影响。主要研究内容如下：

（1）采用水热法制备SnO₂基底，随后，采用二步水热法制备SnO₂@Bi₂O₃异质结材料。通过四因素四水平的正交实验优化工艺参数，以气体传感器对100 ppm乙醇气体的响应值为指标，利用极差分析确定了影响SnO₂@Bi₂O₃异质结气体传感器气敏性能的主要因素是反应时间，最优工艺参数为：[Bi³⁺]/[OH^-]=1:3，[Bi³⁺]浓度=0.015 mol/L，反应温度=160 ℃，反应时间=6 h。将最优参数下制备的SnO₂@Bi₂O₃异质结气体传感器进行气敏性能测试。测试结果表明：该气体传感器对乙醇具有较好的选择性，对100 ppm乙醇气体的响应值为18.3，单一的SnO₂气体传感器响应值为9，最佳工作温度在300 ℃，响应与恢复时间为13 s与7 s，气敏性能的提升得益于异质结的形成。

（2）在优化工艺参数的基础上，探讨了不同浓度（1%、3%、5%）金属元素（Cu、Co、Fe）掺杂对SnO₂@Bi₂O₃复合异质结材料的微观结构和气敏性能的影响。当掺杂浓度为1%、3%与5%时，三种金属元素都能成功地掺入SnO₂@Bi₂O₃异质结材料中。对制成的SnO₂@Bi₂O₃异质结气体传感器的气敏性能进行测试，测试结果表明：5%Cu掺杂时对乙醇具有良好的选择性，气体传感器响应值为21.05，最佳工作温度为290 ℃，响应和恢复时间分别为14 s和8 s。5%Fe掺杂时气体传感器的响应值为22.2，最佳工作温度为290 ℃，响应和恢复时间分别为12 s和11 s 。Fe与Cu的掺杂提升了气敏性能。1%Co掺杂时气体传感器时，响应值只有15.5，最佳工作温度为300 ℃，响应和恢复时间为分别为17 s和6 s。Co掺杂使异质结形成不完全，降低了气敏性能。

Ethanol, as a typical volatile organic compound, is widely used as a solvent and fuel in industries such as pharmaceuticals, coatings, and energy. However, its flammable and explosive properties, coupled with potential health hazards to humans, make rapid detection of its concentration particularly important. SnO₂ is an n-type semiconductor material that, due to its wide bandgap (Eg = 3.6 eV) and low cost, is widely used in gas sensor applications. However, single SnO₂ gas sensors suffer from issues such as poor gas response. To enhance gas sensitivity, this study introduces p-type semiconductor Bi₂O₃, which is combined with SnO₂ to form a pn heterojunction structure. This composite structure improves response to ethanol gas, providing a new approach for reliable ethanol detection.

In this thesis, SnO₂@Bi₂O₃ heterojunction gas sensors were prepared. Through orthogonal experiments, the parameters of the SnO₂@Bi₂O₃ heterojunction were optimised, and the gas-sensing performance of the SnO₂@Bi₂O₃ heterojunction gas sensor was investigated. Additionally, the effects of different metal element dopants on the gas-sensing performance of the SnO₂@Bi₂O₃ heterojunction gas sensor were explored. The main research contents are as follows:

(1) The SnO₂ substrate was prepared using the hydrothermal method, followed by the two-step hydrothermal method to prepare the SnO₂@Bi₂O₃ heterojunction material. Through a four-factor, four-level orthogonal experiment, the process parameters were optimised. Using the response value of the gas sensor to 100 ppm ethanol gas as the indicator, the range analysis determined that the primary factor influencing the gas-sensing performance of the SnO₂@Bi₂O₃ heterojunction gas sensor was the reaction time. The optimal process parameters were: [Bi³⁺]/[OH⁻] = 1:3, [Bi³⁺] concentration = 0.015 mol/L, reaction temperature = 160 °C, and reaction time = 6 h. The SnO₂@Bi₂O₃ heterojunction gas sensor prepared under the optimal parameters was tested for gas sensitivity performance. The test results indicate that the gas sensor exhibits good selectivity towards ethanol, with a response value of 18.3 for 100 ppm ethanol gas, while the response value of a single SnO₂ gas sensor is 9. The optimal operating temperature is 300 °C, with response and recovery times of 13 s and 7 s, respectively. The improvement in gas-sensing performance is attributed to the formation of the heterojunction.

(2) Based on optimised process parameters, the effects of different concentrations (1%, 3%, 5%) of metal elements (Cu, Co, Fe) doping on the microstructure and gas-sensing performance of SnO₂@Bi₂O₃ composite heterojunction materials were investigated. When the doping concentrations were 1%, 3%, and 5%, all three metal elements were successfully doped into the SnO₂@Bi₂O₃ heterojunction materials. The gas-sensing performance of the fabricated SnO₂@Bi₂O₃ heterojunction gas sensors was tested. The test results indicated that at 5% Cu doping, the sensor exhibited excellent selectivity towards ethanol, with a response value of 21.05, an optimal operating temperature of 290 °C, with response and recovery times of 14 s and 8 s, respectively. At 5% Fe doping, the gas sensor response value was 22.2, with an optimal operating temperature of 290 °C, and response and recovery times of 12 s and 11 s, respectively. Fe and Cu doping enhanced the gas-sensing performance. At 1% Co doping, the gas sensor response value was only 15.5, with an optimal operating temperature of 300 °C, with response and recovery times of 17 s and 6 s, respectively. Co doping results in incomplete heterojunction formation, thereby reducing gas-sensing performance.