basically how much boron concentration (10 or 20 or 30 or even more than that)should be there in the bioactive glass to avoid crystallization while sintering above glass transition temperature. kindly share some relevant literature if possible.
The more B2O3 contains the glass from the system SiO2-Na2O-CaO-P2O5, the lower the liquidus temperature (TL) and the temperature of the crystallization. Nevertheless, the crystallization temperature will never drop below 750-800°C and thus always remains significantly higher than Tg (glass transition temperature), which is at 500-550°C.
High concentrations of B2O3 make the glass less stable and sensitive to water. In addition, the combination of large amounts of CaO + B2O3 makes the glass melt less viscous and leads to coarse and rapid crystallization during cooling the melt. In the case of sintering, such glasses also crystallize faster than the glasses with low CaO + B2O3 contents.
This is a vague question. Depends on the glass system - silicates vs. borates vs. phosphates. What you are talking about is basically converting a glass to glass-ceramic. There are a lot of factors that affect the design of glass-ceramic including the phase field of crystallization in which the composition has been designed, and the accordingly the composition of residual glassy phase. In general, boron tends to suppress crystallization in silicate glasses, but again it varies from composition to composition. Therefore, until we have a good idea about the glass composition and the crystalline phase being formed, it is difficult to answer this question.
