We want to fabricate glass transparent containing LaF3 nano-crystals through melting the mixed materials 40SiO2–19Na2CO3–25Al2O3–16LaF3 at 1773K. However , the mixed materials was not melted at 1773K. Instead of high temperature more than 1773K, what should be added to decrease melting point?
Dear Xiangfu Wang
It seems that the base glass, (without considering the addition of 16LaF3) has high viscosity values up to 1700 -1800C.
Please, let me know:
a-composition is mole or weight percent?
b-give me the ranges you can vary Si , Na and Al oxides .
With these data perhaps I am able to determine the composition of base glass with lowest viscosity. Then you can do additions of LaF3 on the base glass.
Regards
Miguel Prado
Dear Miguel Prado,
Thanks for your help. The questions you mentioned are answered as follow:
1. The composition is mole percent.
2. The variational range of the SiO2 is 40-50 mol; The variational range of the Na2CO3 is 18-22 mol; The variational range of the Al2O3 is 15-20 mol. The 16LaF3 is fixed.
Regards,
Xiangfu Wang
Dear Xiangfu
In attachment, there is a Figure with lines. Each line is at constant Temperature.
Red line is at 1600C. Green is at 1500C. All these lines have a log(viscosity)=1Poise wich is a viscosity that allows you to pour the glass from the crucible.
Compositions do not include LaF3 (not included in models).
With these 3 components, it seems that you should choose for example 17.%Al2O3, 33 SiO2, 49 Na2O in order to have reasonable viscosity at 1600C.
Regards
Miguel Prado
Dear Miguel Prado,
Thanks for your help! If we want to fabricate glass transparent containing LaF3 nano-crystals, how to confirm the composition of the LaF3 powder?
Regards,
Xiangfu Wang
Dear Xiangfu, one question: your composition is entirely oxides / fluorides except the Na2CO3. Including the Na2CO3 makes your composition sum to 100%. However, during melting this Na2CO3 will decompose and evolve the carbonate as CO2. My question is: is it possible your glass composition should be 40SiO2-16Na2O-25Al2O3-16LaF3 instead of the one you have stated? This may be the cause of your melting difficulties, since the glass you have been trying to make may be lower in Na2O than it should be? Kind Regards, Paul.
The mentioned composition is very common for fluoro-alumino-silicate based transparent glass ceramics. There are many reports. I also have prepared the similar glasses and transparent glass-ceramics with even lesser alkali oxide contents. The melting temperature of 1773 K (1500 C) is sufficient for this composition. One of the possibility in above case may be the actual temperature is not the same as programmed one. Platinum crucible is best for melting such batches. Also the use of Al(OH)3 instead of Al2O3 is helpful to accelerate the reaction.
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