[Display omitted] • Diaspore and kaolinite can transform into Na 2-x Al 2-x Si x O 4 by reacting with Na 2 CO 3. • The transformation is affected by temperature and the amount of Na 2 CO 3. • The leaching performance of Na 2-x Al 2-x Si x O 4 is negatively correlated with x value. A series of sodium aluminosilicates (Na 2-x Al 2-x Si x O 4 , x = 0.85, 0.55, 0.45, 0.35, 0.25 and 0.05) can be generated in the soda sintering process, some of which can be dissolved in sodium aluminate solution. This paper focuses on the transformation of aluminum-bearing minerals into Na 2-x Al 2-x Si x O 4 during the calcination of diasporic bauxite with different proportions of Na 2 CO 3 at 400–1100 °C. Based on thermodynamic analysis, the thermal behaviors, phase transformations and bonding changes of the aluminum-bearing minerals are investigated using thermogravimetric analysis and differential scanning calorimetric (TGA-DSC), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) techniques. In addition, the dissolution performances of some Na 2-x Al 2-x Si x O 4 are verified by water leaching. The results demonstrate that the aluminum-bearing minerals in diasporic bauxite are diaspore and kaolinite, which are converted into Na 2-x Al 2-x Si x O 4 after calcination with Na 2 CO 3 at 700–1100 °C. Increasing the calcination temperature in the range of 700–1000 °C and the proportion of Na 2 CO 3 results in Na 2-x Al 2-x Si x O 4 having lower x value and decomposing into NaAlO 2 and Na 2 SiO 3 if Na 2 CO 3 is present in excess. As the mass ratio of bauxite to Na 2 CO 3 is 1, Na 1.95 Al 1.95 Si 0.05 O 4 is primarily formed at 900–1000 °C, which has excellent dissolution performance, close to that of NaAlO 2. Upon further increasing the calcination temperature to 1100 °C, Na 1.95 Al 1.95 Si 0.05 O 4 transforms into Na 2-x Al 2-x Si x O 4 with a higher x value, which has worse dissolution performance. [ABSTRACT FROM AUTHOR]