The use of a single ammonium acidic salt towards simple green co-precipitation synthesis for Mn-activated fluorides

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 49; no. 18; pp. 5823 - 5831
• Main Authors: Deng, T. T, Song, E. H, Zhou, Y. Y, Chen, J. Y, Cheng, Y. F, Yuan, J, Fan, T
• Format: Journal Article
• Language: English
• Published: 14.05.2020
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d0dt00986e

Herein, a simple green co-precipitation route for Mn 4+ -activated fluorides has been realized via individually using the aqueous acidic salt NH 4 HF 2 as a solvent. The systematic explorations of ionization, erosion, solvent concentration, solvency on reactants, and reaction with an extra weak acid disclosed that the near-saturated aqueous NH 4 HF 2 , ionizing into abundant HF 2 − , H + , and F − ions, exhibited large dissolving capacity and good stabilization on Mn 4+ without obvious toxicity. The green synthesized example of Cs 2 GeF 6 :Mn 4+ emitted a typical narrow band red light at 633 nm with normal optimal doping at ∼8 at%. Compared with its contrast prepared from the HF system, it experienced only ∼10% reduction in quantum efficiency and slight emission attenuation below 150 °C as the more humidity-sensitive weaker acid surface aroused lattice thermal vibration. The further action as red component fabricated a high-quality warm white light-emitting diode (W-LED) with a high color rendering index (Ra ∼ 91), high luminous efficacy (∼149 lm W −1 ), low correlated color temperature (∼3211 K), and good color stability against the operating environment. Combined with the universal synthesis of A 2 XF 6 :Mn 4+ (A = K, Rb, Cs; X = Si, Ge), our findings can probably open up a simple and feasible green synthetic strategy for efficient Mn 4+ -doped fluorides using acidic salts. Simply using acidic salt NH 4 HF 2 contributes to the green co-precipitation synthesis of Mn 4+ -doped fluorides for W-LED applications.