The frit CF exhibited a lower relative density than the frit PF in the temperature range of the maximum sintering because the frit CF contained coarser particles than the frit PF. This result is in agreement with the model proposed by Prado and Zanotto[13], where the increase in particle size reduces the sintering rate. However, we observed that the specimens reached relative densities between 0.93 and 0.96 above 8501C, and the maximum values were achieved at 10001C. In this case, the reduction of surface area with increasing temperature should have significantly reduced the crystallization rate. Thus, this phenomenon should have reduced the negative effect on sintering and allowed the relative density to increase