Synthesis and characterization of nano-LaFeO3 powders by a soft-chemistry method and corresponding ceramics

The preparation of a nano-sized LaFeO3 powder by a soft-chemistry method using starch as complexing agent is described herein. Phase evolution and development of the specific surface area during the decomposition process of (LaFe)-gels were monitored up to 1000 °C. A phase-pure nano-sized LaFeO3 powder with high specific surface area of 25.7 m2/g and a crystallite size of 37 nm was obtained after calcining at 570 °C. TEM investigations reveal a porous powder with particles in the range of 20 to 60 nm. Calcinations to 1000 °C result in crystallite sizes up to 166 nm. The dilatometric measurements of the sintering behaviour show that the beginning of shrinkage of pellets from the nano-sized powder is downshifted by more than 300 °C compared to the coarse-grained mixed-oxide powder. The orthorhombic ⇆ rhombohedral phase transition was observed at 980 °C in DTA measurements for the coarse-grained ceramic bodies. The enthalpy change (ΔH) during the phase transition and the thermal expansion coefficient (αdil) for the ceramics were determined as 410 J/mol and 11.8·10− 6 K− 1, respectively. Whereas the enthalpy changes during the phase transition of the nano-sized LaFeO3 powders are ≤ 200 J/mol.

► Novel, eco-friendly and simple synthesis route for nano LaFeO3 powders using starch as complexation agent ► Monitoring the phase evolution during the synthesis ► Nano LaFeO3 powder with high sintering activity obtained after calcination at 570 °C ► Dense ceramic bodies even at 1250 °C without any sintering additive ► Investigations of phase transition and the thermal expansion coefficient