Structure and photoluminescence of mullite-Ge nanocomposite

Al12Si3.75Ge0.25O26 ceramic powder was prepared by sol-gel method using Al(NO3)3,Si(OC2H5)4 and Cl3GeCH2-CH2COOH as precursors.The structural formation of Al12Si3.75Ge0.25O26 ceramic powder was analyzed by XRD.After reduction by flowing H2/Ar mixture gas,strong room temperature photoluminescence (PL) can be observed at 565 nm,613 nm,682 nm,731 nm and 777 nm,respectively.The PL intensity scarcely depends on the reduction temperature and duration,while the sample reduced at 500 ℃ for 3 hours has the highest PL intensity.Before and after reduction at 500 ℃,the volume of unit cell of mullite solid solution decreases to 0.4699 (A)3.Based on the analysis of XPS and Raman spectra,it can be approved that the PL phenomenon at room temperature is caused by the embedded Ge nanoparticles with the average size of about 1.95 nm.