<p>A high-performance room temperature ammonia (NH₃) gas sensor based on ZnO/Zn₂SnO₄ composite was synthesized by a one-step hydrothermal method by combining simply prepared zinc oxide (ZnO) with zinc stannate (Zn₂SnO₄), which has a high gas-sensitive performance at room temperature. The experimental results show that the response value of ZnO/Zn₂SnO₄ for 1000 ppm NH₃ is 4364.6, and the response/recovery time is 1.4&#xa0;s/1.2&#xa0;s, respectively, and a minimum detection limit of 0.16 ppm. This is better than that of pure Zn₂SnO₄, which has a response value of 151.8, and it is difficult to reach the equilibrium during the adsorption process. Thus, the response/recovery time of ZnO/Zn₂SnO₄ is faster than that of the current metal oxide semiconductor-based gas sensors. This is due to more oxygen vacancies and oxygen radicals on the ZnO/Zn₂SnO₄ surface. In addition, the synergistic effect between ZnO and Zn₂SnO₄ heterojunction accelerates the carrier migration efficiency and improves the gas-sensitive performance. Thus, the ZnO/Zn₂SnO₄ sensor combines the advantages of room-temperature operation and the simplicity of preparation, and at the same time broadens the application of Zn₂SnO₄ in the sensor field.</p>