Mössbauer Spectroscopic Study of the Ordering Degree in Sr_2–<i>x</i>Ba<i>_x</i>FeNbO₆ Double Perovskites Prepared via the Sol–Gel Method

Sr_2-<i>x</i>Ba<i>_x</i>FeNbO₆ double perovskite materials were synthesized for the first time by using the sol-gel method, and their ordering degree was analyzed with Mössbauer spectroscopy. By analyzing the changes in the Fe ion quadrupole splitting before and after Ba²⁺ doping, Mössbauer spectroscopy was used to quantify the ordering degree of the double perovskite materials. The double perovskite samples prepared by the novel sol-gel method exhibited a high degree of ordering. VSM measurements confirmed the Mössbauer results, revealing a significant correlation between the square of the slope of the magnetization curve and the ordering degree obtained from Mössbauer spectroscopy, further validating the feasibility of using Mössbauer spectroscopy for quantitative analysis of the ordering degree in double perovskite samples. This study not only overcomes the previous challenge of synthesizing Sr₂FeNbO₆ via the sol-gel method but also offers a new perspective for investigating the ordering degree of double perovskite materials through Mössbauer spectroscopy.