High-temperature phase transition of lanthanum niobium titanate La-0.64(Ti-0.92,Nb-0.08)O-3 has been studied using neutron powder diffraction and the Rietveld method. The material is orthorhombic (Cmmm) between 295 and 534 K, while it is tetragonal (P4/mmm) between 637 and 740 K. The anti-phase tilt along the b axis of the oxygen octahedron around Ti and Nb atoms was found to induce the tetragonal-to-orthorhombic phase transition. The angle of the tilt and the b/a ratio of cell parameters decrease with an increase of temperature and become 0degrees and unity, respectively, at a transition temperature between 534 and 637 K. (C) 2003 Elsevier Science B.V. All rights reserved.