The reaction between TiF3 or TiO2 and Ce3+ in sodium hydroxide solutions yields highly crystalline NaCeTi2O6 at room temperature and under mild hydrothermal conditions (T less than or equal to 240 degreesC). There is no evidence for the formation of ternary Ce-Ti-O materials by this method, and the use of bases other than NaOH always produces poorly crystalline materials. The material NaCeTi2O6 has a distorted perovskite structure with sodium and cerium ions randomly occupying the A sites: Pnma, a = 5.4517(8) Angstrom, b = 7.7292(6) Angstrom, c = 5.4573(3) Angstrom. XANES spectroscopy at the Ti K edge and Ce L-III edge, with reference to crystalline model compounds, reveals that cerium is found solely as Ce(III) and titanium as Ti(IV) in NaCeTi2O6. Isomorphous substitution of Ce3+ by Nd3+ or Ti4+ by V4+ is found to be very facile under hydrothermal conditions (at a temperature of 240 degreesC), by addition of appropriate amounts of metal salts to the hydrothermal reaction mixtures. The series NaCe1-xNdxTi2O6 (0 less than or equal to x less than or equal to 1) and NaCeTi2-xVxO6 (0 less than or equal to x less than or equal to 1.8) can be formed directly in one step, and all materials were characterized by powder X-ray diffraction. The oxidation states of the substituent elements were determined using XANES spectroscopy, which further demonstrates that isomorphous substitution has taken place, with all vanadium present as V(IV) when the B site is substituted. Scanning electron microscopy analysis of the solids shows them to be made up of irregularly shaped particles made up of clusters of submicron-sized crystallites but that on firing in excess of 1000 degreesC the particle size is increased to similar to10 mum and the particles have distinct, sharp edges.