Synthesis and characterization of Eu3+-doped glass ceramics from the system CaO-GeO2-Li2O-B2O3

Three Eu ³⁺ doped glass compositions from the system CaO-GeO ₂-Li ₂O-B ₂O ₃ were thermally treated for obtaining of the nano glass-ceramics. A series of glass ceramics were obtained under different heat treatment conditions for each glass composition. The main crystallizing phases in the three investigated compositions were Ca ₂GeO ₄, Ca ₅Ge ₃O ₁₁ or Li ₂CaGeO ₄. Research was aimed at finding the optimal thermal treatment conditions of parent glasses for preparing of glass-ceramics with optimal particle size, degree of crystallization and transparency determining high emission intensity. For this, a stepwise heat treatment was applied to obtain a series of glass-ceramic samples from the same starting glass composition. Under such treatment, the kinetics of nucleation and growth of the crystallizing phase were tracked. DTA, XRD, TEM, UV–vis analyses were used for characterization of the obtained series of glass-ceramics. Based on the results, it was concluded that the main factors determining the behavior of the crystallizing nanophase (predominant new nucleation or predominant growth of already appeared seeds) are the thermal treatment conditions and the composition and structure of the parent glass, and not so much the composition and structure of the crystallizing phase.