Low‐Temperature Synthesis of Bismuth Titanate Niobate (Bi ₇ Ti ₄ NbO ₂₁ ) Nanoparticles from a Metal‐organic Polymeric Precursor

This paper describes the preparation of homogeneous Bi 7 Ti 4 NbO 21 single‐phase ceramic powders of ∼55 nm crystallite size, at temperatures as low as 400°–500°C using a metal citrate complex method based on the Pechini‐type reaction route. The thermal decomposition/oxidation of the polymerized resin, as investigated by TG/DTA, XRD, and SEM, led to the formation of a well‐defined orthorhombic Bi 7 Ti 4 NbO 21 compound with lattice parameters a = 0.544, b = 0.540, and c = 2.905 ± 0.0005 nm. Reaction takes place through an intermediate binary phase with a stoichiometry close to Bi 20 TiO 32 which forms between 300° and 375°C. The metal‐organic precursor synthesis method, where Bi, Ti, and Nb ions are first chelated to form metal complexes and then polymerized to give a gel, allows control of the Bi/Ti/Nb stoichiometric ratio leading to the rapid formation of nanosized bismuth titanate niobate (Bi 7 Ti 4 NbO 21 ) ceramic powders, at temperatures much lower than usually needed by conventional processing of mixed‐oxide powders.