Features of the phase transformations in titanium-containing zinc aluminosilicate glasses doped with cobalt oxide

We demonstrated the efficiency of the Raman spectroscopy method in the study of the process of the formation of the amorphous zinc aluminotitanate (ZAT) phase during the phase decomposition of the titanium-containing zinc aluminosilicate glasses doped with cobalt oxide. The quantitative dependences of the variation of the intensity of the Raman bands characteristic for amorphous and crystalline phases on the temperature of the thermal treatment and the cobalt oxide concentration have been obtained. The speed of phase decomposition with the separation of the nanosize crystals of zinc aluminate spinel (gahnite) and ZAT phase increases at low-temperature thermal treatments with increasing cobalt oxide concentration. The addition of cobalt oxide increases the amount of the amorphous ZAT phase separated during phase decomposition and increases its thermal stability during high-temperature treatments. It has been shown that the Co2+ ions enter the zinc aluminate spinel (gahnite) crystals precipitated during phase decomposition. It has been supposed that the composition of the residual glass is close to that of the quartz glass and it contains a very small amount of titanium-oxygen tetrahedra.