Non-isothermal crystallization kinetics growth of LiYF4(Yb,Er) nanoparticles

Abstract The crystallization process of Yb 3+ /Er 3+ codoped LiYF 4 nanoparticles obtained by sol-gel method was studied using differential scanning calorimetry and X-ray diffraction. Thermal data obtained from differential scanning calorimetry measurements under non-isothermal conditions at different heating rates were examined using both model-free and model fitting approaches. It was shown that LiYF 4 phase crystallization occurs at around 383 °C as a result of the thermal decomposition of trifluoracetates and is shifted to higher temperatures as the heating rate increases. Both Friedman and Ozawa-Flynn-Wall analyses have indicated that the activation energy and pre-exponential factor decrease slightly as the crystallization proceeds. According to the model-fitting approach (by using extended Prout-Tompkins nth-order, ath autocatalysis reaction), LiYF 4 nanocrystalline phase is the result of an autocatalytic process where a second metastable phase YF 3 acts as a catalyst that accelerates the crystallization process of the LiYF 4 phase.