Fig. 7 presents the SEM micrographs of samples with different firing temperatures of 1160 C, 1220 C and 1280 C. It could be shown that the discrete droplet phase separation structures were formed in every sample [20]. Additionally, with the increase of firing temperature, the average diameter of the phase separation droplets increased while the density decreased in the glazes, which were due to the decreased viscosity of the molten glazes at higher firing temperatures.Therefore, the movement speed of particles got faster so that the discrete phase droplet could easily move to the surface of phosphate glass [21].