Low temperature synthesis of lead titanate by a hydrothermal method

Alkoxide-based hydrothermal powder synthesis of lead titanate was investigated. The objective of this work was to lower the synthesis temperature. By modifying titanium isopropoxide with acetylacetone during solution mixing, the phase-pure lead titanate with perovskite structure was synthesized at temperatures as low as 150 degrees C. It was determined that the pH of the hydrothermal reaction medium and the initial Pb/Ti ratio are critical factors in forming stoichiometric PbTiO3. When the pH of the initial feedstock is above 14 and the Pb/Ti ratio is greater than 1.5, a phase-pure PbTiO3 can be obtained. The modification of titanium alkoxide gave rise to the formation of a stable complex against hydrolysis and eventually reduced the synthesis temperature significantly. A possible formation mechanism for PbTiO3 is the dissolution-recrystallization from an amorphous precursor to a well-crystalline product as originally proposed by Rossetti et al. Hall-Williamson analysis was also performed on the hydrothermally derived PbTiO3 to interpret the systematic peak broadening and asymmetry for {001} reflections, unlike the commercial PbTiO3. It was observed that the strain in the c-axis direction is much higher than that in the a-axis direction while the domain sizes for both directions are similar. This strain anisotropy exerted in the particles may indicate a unique domain structure in the hydrothermally synthesized particles in which either only 180 degrees domains exist or possibly only a single domain.