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Intercony-meeting 30. Mai 2008

Intercony-meeting 30. Mai 2008. Roman Wurth Prof. C. Rüssel Otto-Schott-Institut. Intercony-meeting. Crystallization of lithiumalumosilicat-glass as a model for low- a glass-ceramics Crystallization of (Pb, Cd, Yb)F x -glasses for the formation of up-conversion glasses

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Intercony-meeting 30. Mai 2008

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  1. Intercony-meeting30. Mai 2008 Roman Wurth Prof. C. Rüssel Otto-Schott-Institut

  2. Intercony-meeting • Crystallization of lithiumalumosilicat-glass as a model for low-a glass-ceramics • Crystallization of (Pb, Cd, Yb)Fx-glasses for the formation of up-conversion glasses they transfer light of large wavelength to light of short wavelength

  3. Lithiumalumosilicat-Glassmodel glass for low-a glass-ceramics http://www.news-reporter.net/downimg.las?size=small&imageID=1632

  4. XRD • Change between high and low crystal modifications at 925 °C b-spodumen SS b-quartz SS

  5. Solid State NMR • The base glass shows a chemical shift of -1 ppm -> coordination-number of 6 • Typical for glass • After tempering the chemical shift of 6Li is 0 ppm -> coordination number of 4 • Coordination number of Li in β-quartz SS • All Li+ is in the crystal phase after tempering

  6. Rietveld Refinement • Simulation of the β-Quartz SS • CAS-Number 74-1095 (LiAlSi2O6) • hexagonal space group P6222 • a = 5,182; c = 5,431 750 °C, 4h

  7. Size of particles • Only small growth of nanoparticles with tempering time • Glass ceramic is still transparent after tempering 750°C, 8h

  8. Percentage of crystal phase • Large amount of the glass crystallizes with tempering time • After 120h 82% is crystallized

  9. Shift of peaks with tempering time • Shown: 100 % peak at around 25.5 degree • Shift to larger 2q-values with tempering time -> unit cell is shrinking

  10. Cell parameters vs. tempering time • Cell parameter a decreases with tempering time • Cell parameter c remains constant

  11. Percentage of Li+, Mg2+, Si4+ • Formula: LixMgyAlx+2ySi1-x-2yO2 • Percentage of Si4+ increases with tempering time, percentage of Li+ decreases

  12. Cell parameters vs. percentage of Si4+ • Cell parameter a shrinks with increasing percentage of Si4+, cell parameter c stays constant • With increasing Si4+ the size of the elemental cell shrinks

  13. Volume elemental cell vs. tempering time • Tg can not be messured with dilatometry after tempering longer than 2 h at 750°C

  14. Number of crystals • Number of crystal particles in 100 mm3 with annealing time

  15. (Pb, Cd, Yb)Fx-glass 405 °C, 72 h

  16. Upconversion

  17. Future Work • Use of different methods to determine the Tg of the glass (mainly DSC) • Use of solid-state-NMR to get a better understanding of the structure • Impedance messurements at fixed temperatures and variable times to examine the crystalization process in the glass • TEM-messurements to make the crystals visible • (Pb, Cd, Yb)Fx-glass: ASAX-measurements under preperation

  18. Thanks for your attention

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