Solid-state synthesis of LaFeO₃: unraveling the impact of calcination temperature on phase formation and dielectric properties

Abstract Calcination temperature plays a crucial role in the synthesis of ceramic materials by influencing phase purity, grain size, and dielectric properties. This study investigates the effect of calcination temperature on the structural and dielectric characteristics of LaFeO 3 to identify the optimal temperature for achieving phase purity and enhanced dielectric performance. LaFeO 3 powders were synthesized via the solid-state reaction method and subjected to calcination at temperatures of 850 °C, 950 °C, 1050 °C, 1150 °C, and 1250 °C for 3 hours. X-ray diffraction (XRD) analysis indicated the presence of secondary phases at temperatures below 1150 °C, while a pure orthorhombic perovskite phase was obtained at 1150 °C and above, with enhanced crystallinity at 1250 °C. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) analyses, conducted on samples calcined at 1150 °C and 1250 °C, confirmed that increasing the calcination temperature resulted in grain growth and enhanced phase purity, with a noticeable increase in oxygen vacancies at 1250 °C. Impedance spectroscopy revealed that the sample calcined at 1150 °C exhibited higher electrical resistance, whereas the sample calcined at 1250 °C demonstrated increased electrical conductivity due to reduced grain boundary resistance. The dielectric constant ( ε′ ) was higher at 1250 °C, attributed to the increased grain size and improved structural ordering, while the dielectric loss tangent (tan δ ) increased at low frequencies. Modulus analysis confirmed a reduction in grain boundary relaxation effects at 1250 °C, facilitating faster charge transport, while AC conductivity analysis indicated that higher calcination temperatures facilitated charge transport via a long-range hopping mechanism. These findings suggest that calcination at 1150 °C is the minimum required temperature to achieve phase purity, whereas calcination at 1250 °C enhances the dielectric properties significantly.