The influence of temperature on the structural behaviour of sodium tri- and hexa-titanates and their protonated forms

The thermal stability of Na2Ti3O7 and Na2Ti6O13, together with that of their protonated forms was investigated. The influence of temperature on the structural behaviour of tri- and hexa-titanates was studied using DTG, XRD, FTIR and FT-Raman. These results were correlated with the nature of the exchangeable cations using elemental analysis and N2-sorption. The tunnel structure of Na2Ti6O13 revealed a higher thermal stability compared to the layered structure of Na2Ti3O7 that shows traces of dimerisation above 800 °C. The sodium forms were observed to be more thermally stable compared to their protonated forms. However, analysis show that ‘H2Ti6O13’ is much more thermally stable than the layered H2Ti3O7 which go through structural changes above 250 °C and suffer a complete structural collapse into anatase/rutile above 800 °C. It was obvious that thermal stability was significantly influenced by the nature of the exchangeable cations and the degree of ion-exchange.