In-situ crystallization of CoCr2O4 in tellurite glass with enhanced optical nonlinear limiting, photoluminescence, and magnetic properties: Influence of Co content

This article reports the in-situ growth of spinel CoCr 2 O 4 nanocrystals (NC) in tellurite glass through tailoring the Co content by melt-quenching method. The microstructure, optical, and magnetic properties of NC/ glass systems were systematically studied using various techniques. Well-defined 30 nm crystallization of CoCr 2 O 4 (space group of Fd3m ) homogeneously distributed in the glassy matrix and the concurrent formation of cubic BiCoO 3 (space group of P4mm ) when the Co content exceeds 3%. The coexistence of multivalence and coordination states of Co and Cr significantly modified the glass structure with conversion of TeO 4 →TeO 3 , BO 4 →BO 3 , and CoO 4 →CoO 6 units. Exceptional performance of the glass containing 5% Co-tuned CoCr 2 O 4 was obtained, showcasing the decrease of E g (2.09 eV), strong ferro-magnetization of 7.04 emu/g, large α 3 (4.88×10 −10 m/W) and good optical limiting property (threshhold of 1.31×10 12 W/m 2 ). Furthermore, the same glass showed excellent red emission between 650 and 800 nm under the excitation of 460 nm, with an increased lifetime (2.648 ms) and good stability of 90.7% within 25–300 °C. The emission mechanism was discussed. EPR analysis confirmed the active role and spin-states of magnetic Cr and Co ions , contributing synergistically to the improved optical and magnetic properties of the glasses.