Study on the Structural Analysis of CaO-SiO2-TiO2 Glasses by X-Ray Photoelectron Spectroscopy

In a previous paper, three kinds of oxygen, i.e. O0, O− and O2− in binary silicate glasses were analyzed quantitatively by using XPS. In the present paper, the effect of TiO2 on the silicate structure was investigated for CaO-SiO2-TiO2 glasses in the same way as analyzed previously. It was found that the O1s spectra obtained by XPS was able to be separated into four kinds of oxygen ions spectram according to specification for binding state of oxygen ions, that is, Si-O-Si, Si-O−…Ca2+, Si-O-Ti (or Si-O−…Ti4+) and Ti-O−…Ca2+. The rate for existence of these oxygen ions analyzed from the O1s spectra was in good agreement with the distribution of oxygen ions, which was calculated from the existence ratio of tetrahedrally coordinated Ti4+ ion (Ti(4)) to octahedrally coordinated Ti4+ ion (Ti(6)) with reference to the results of electrical conductivity measurement of CaO-SiO2-TiO2 melts. From the results of the above analysis, the behaviour of TiO2 was explained in the range of three compositions as follows: (1) In the case of CaO/SiO2=1, Ti(4) existed at the same ratio as Ti(6). It means that TiO2 added to the CaO-SiO2 system did not act as network former or modifier on the silicate anions but existed as titanate ions having Ti-O−…Ti4+ bond. (2) In the case of CaO/SiO21, the amount of Ti(4) became larger than that of Ti(6), and the excess Ti(4) constituted titanate anions and made Ti-O−…Ca2+ bond.