Structural transformations and optical properties of glass-ceramics based on ZnO, β- and α-Zn2SiO4 nanocrystals and doped with Er2O3 and Yb2O3: Part I. The role of heat-treatment

Publication date: October 2018
Source:Journal of Luminescence, Volume 202
Author(s): Pavel Loiko, Olga Dymshits, Anna Volokitina, Irina Alekseeva, Darya Shemchuk, Marina Tsenter, Anastasia Bachina, Alexander Khubetsov, Elena Vilejshikova, Pavel Petrov, Alexander Baranov, Alexander Zhilin
Differential scanning calorimetry, X-ray diffraction analysis, transmission electron microscopy, high- and low-frequency Raman and optical spectroscopy were applied to the study of structural transformations in glass of the K2O – ZnO – Al2O3 – SiO2 system codoped with Er2O3 and Yb2O3 and subjected to heat-treatments at 680–1300 °C. Transparent glass-ceramics based on ZnO nanocrystals are prepared by heat-treatments at 680–800 °C, while at 860–900 °C, β-Zn2SiO4 (β-willemite) nanocrystals precipitate in addition to ZnO; α-Zn2SiO4 nanocrystals appear additionally at 950 °C, and the material loses transparency. Opaque glass-ceramic prepared by heat-treatments at 1000 °C contains only crystals of ZnO and α-Zn2SiO4, while crystallization of potassium aluminosilicates, KAlSi2O6 (from the surface) and KAlSiO4 (from the bulk) in addition to ZnO and α-Zn2SiO4, is observed at above 1000 °C. Optical absorption and luminescence of the initial glass and GCs are reported. A shift of the UV absorption edge and the near-IR losses due to the free charge carrier scattering are indications of the ZnO crystallization. Multiple visible emissions from the glass and GCs are determined by the Er³⁺ ions, nanocrystals of α-Zn2SiO4 and defects of the ZnO nanocrystals. The color of the latter emission can be tuned by varying the heat-treatment temperature. The rare-earth ions (RE³⁺) do not enter into the Zn-containing nanocrystals and remain in the residual glassy phase until ~ 1200 °C, when the RE silicates (RE2Si2O7) are formed resulting in structured intense Er³⁺ emission.



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