Ammonia-based direct reduction (ADR) of iron oxides is a promising method for sustainable ironmaking, offering a hydrogen carrier with high energy density and ease of transportation. However, the challenge lies in understanding the reaction kinetics and nitrogen incorporation during reduction. This study investigates the effects of temperature on reduction efficiency and nitride formation through phase, local chemistry, and gas evolution analysis. The effects of inherent reactions and diffusion on phase formation and chemistry evolution are discussed in relation to reduction temperature. The work also discusses nitrogen incorporation into the material, which occurs through both spontaneous and in-process nitriding, fundamentally affecting the structure and chemistry of the reduced material. The effect of nitrogen incorporation on the reoxidation tendency of the ammonia-based reduced material is investigated and compared with that of the hydrogen-based reduced counterpart. The results provide a fundamental understanding of the reduction and nitriding for iron oxides exposed to ammonia at temperatures from 500 to 800 °C, serving as a basis for exploitation and upscaling of ammonia-based direct reduction for future green steel production. The study focuses on two main aspects: (1) the fundamental mechanisms controlling the reduction capabilities of iron oxides with ammonia at temperatures from 500 to 800 °C, particularly the microstructural transformations controlled by the chemical interaction of the oxide material with the reducing gas during the reduction process that stems from the ammonia decomposition into hydrogen and nitrogen species in dependency of temperature. (2) The final nitriding effect during cooling, which has been documented in previous research. The effects of such nitriding on the final state of the reduced material and the possibilities of avoiding this final nitriding by gas purging with inert Ar gas are investigated. The implications of nitriding are also explored in relation to the reoxidation properties of the final reduced ore and compared with the reduced material via HyDR. The reduction experiments were performed in a thermogravimetric analysis (TGA) system with a quartz tube furnace and a weight balance. The experiments were performed on individual commercial hematite pellets with weights ranging from 2.6 to 2.9 g and an average diameter of 11 mm. The reduction experiments were performed with a heating rate of 5 °C/s up to temperatures from 500 to 800 °C with a holding time of 1 to 10 h at a pressure of 1 bar. For the HyDR process, 99.999% pure H₂ gas was continuously used, and for the ADR process, 99.999% pure NH₃ gas was continuously used during the entire reduction procedure. The reduction gas was introduced to the system, and the chamber was flushed completely before the heating of the samples occurred. The flow rate for the reduction and purging gases was 10 L/h (0.166 SLM). After the holding time, the infrared heating was switched offAmmonia-based direct reduction (ADR) of iron oxides is a promising method for sustainable ironmaking, offering a hydrogen carrier with high energy density and ease of transportation. However, the challenge lies in understanding the reaction kinetics and nitrogen incorporation during reduction. This study investigates the effects of temperature on reduction efficiency and nitride formation through phase, local chemistry, and gas evolution analysis. The effects of inherent reactions and diffusion on phase formation and chemistry evolution are discussed in relation to reduction temperature. The work also discusses nitrogen incorporation into the material, which occurs through both spontaneous and in-process nitriding, fundamentally affecting the structure and chemistry of the reduced material. The effect of nitrogen incorporation on the reoxidation tendency of the ammonia-based reduced material is investigated and compared with that of the hydrogen-based reduced counterpart. The results provide a fundamental understanding of the reduction and nitriding for iron oxides exposed to ammonia at temperatures from 500 to 800 °C, serving as a basis for exploitation and upscaling of ammonia-based direct reduction for future green steel production. The study focuses on two main aspects: (1) the fundamental mechanisms controlling the reduction capabilities of iron oxides with ammonia at temperatures from 500 to 800 °C, particularly the microstructural transformations controlled by the chemical interaction of the oxide material with the reducing gas during the reduction process that stems from the ammonia decomposition into hydrogen and nitrogen species in dependency of temperature. (2) The final nitriding effect during cooling, which has been documented in previous research. The effects of such nitriding on the final state of the reduced material and the possibilities of avoiding this final nitriding by gas purging with inert Ar gas are investigated. The implications of nitriding are also explored in relation to the reoxidation properties of the final reduced ore and compared with the reduced material via HyDR. The reduction experiments were performed in a thermogravimetric analysis (TGA) system with a quartz tube furnace and a weight balance. The experiments were performed on individual commercial hematite pellets with weights ranging from 2.6 to 2.9 g and an average diameter of 11 mm. The reduction experiments were performed with a heating rate of 5 °C/s up to temperatures from 500 to 800 °C with a holding time of 1 to 10 h at a pressure of 1 bar. For the HyDR process, 99.999% pure H₂ gas was continuously used, and for the ADR process, 99.999% pure NH₃ gas was continuously used during the entire reduction procedure. The reduction gas was introduced to the system, and the chamber was flushed completely before the heating of the samples occurred. The flow rate for the reduction and purging gases was 10 L/h (0.166 SLM). After the holding time, the infrared heating was switched off