AbstractReal-time monitoring of combustion products and composition is critical to emission reduction and efficient energy production. The fuel efficiency in power plants and automobile engines can be dramatically improved by monitoring and controlling the combustion environment. However, the development of novel materials for survivability of oxygen sensors at extreme environments and demonstrated rapid response in chemical sensing is a major hindrance for further development in the field. Gallium oxide (Ga₂O₃), one among the wide band gap oxides, exhibit promising oxygen sensing properties in terms of reproducibility and long term stability. However, the oxygen sensors based on β-Ga₂O₃ and other existing materials lack in response time and stability at elevated temperatures. In this context, we demonstrate an approach to design materials based on Ti-doped Ga₂O₃, which exhibits a rapid response and excellent stability for oxygen sensing at elevated temperatures. We demonstrate that the nanocrystalline β-Ga₂O₃ films with 5% Ti significantly improves the response time (~20 times) while retaining the stability and repeatability in addition to enhancement in the sensitivity to oxygen. These extreme environment oxygen sensors with a rapid response time and sensitivity represent key advancement for integration into combustion systems for efficient energy conversion and emission reduction.