Synthesis, luminescence properties, and thermal decomposition kinetics of NH4GdF4:Eu3+with an intense negative thermal quenching effect

Developing Eu3+-doped red emission phosphors with exceptional luminescence thermostability is crucial for advancing white light emitting diodes (WLEDs). Herein, a series of NH4GdF4:xEu3+ (NGF:Eu3+) compounds are synthesized using the co-precipitation method, with NGF:0.25Eu3+ identified as the most promising sample. The paper discusses the mechanism underlying the negative thermal quenching (NTQ) effect, indicating that NGF:0.25Eu3+ exhibits sufficient luminescence thermal stability and chemical resistance under the operational temperatures of WLEDs, making it a viable application for this purpose. Experimental results reveal the following key findings. (a) Supported by the NTQ effect, NGF:0.25Eu3+ exhibits remarkable luminous thermostability. The integrated emission intensities at 150 degrees C, 180 degrees C, and 121 degrees C are 210.6 %, 234.1 %, and 244.2 % respectively, of the initial intensity at 30 degrees C. (b) NGF:0.25Eu3+ demonstrates good chemical thermostability and sufficient luminescent thermal stability under WLED operational temperatures and commences decomposition at 200 degrees C, making it suitable for use in WLEDs. (c) An assembled prototype WLED combining NGF:0.25Eu3+ and YAG:Ce3+ (a yellow emitting phosphor), emits warm white light under ultraviolet excitation. Furthermore, this study delves into the thermal decomposition kinetics of NGF:0.25Eu3+ using an iterative approach, identifying a single-step reaction mechanism. Consequently, the study provides three kinetic parameters (E alpha, g(alpha), and A) and three thermodynamic functions (Delta H#, Delta S#, and Delta G#) associated with the decomposition process.