Structural, dielectric and magnetic properties of Ta-substituted Bi0.8La0.2FeO3 multiferroics

• Ta substitution on the structural and dielectric properties of Bi0.8La0.2FeO3 (BLFO).
• Ta5+ slows down the oxygen ion motion consequently reducing grain growth.
• Ferroelectric transition temperature shifts towards higher temperatures with Ta.
• Ta doped BLFO has enhanced resistivity, dielectric properties and remanent magnetization.

The role of doping Ta in Fe-site on the phase, microstructure and dielectric properties of Bi0.8La0.2FeO3 (BLFO) has been investigated in this research. Single phase Bi0.8La0.2Fe1−xTaxO3 (BLFTO) ceramics with x = 0.0, 0.01, 0.03 and 0.05 were synthesized by conventional solid-state reaction method. The BLFTO dried pellets were calcined at 800 °C for 2 h and then sintered at 1000 °C for 2 h. Phase analysis by X-ray diffraction (XRD) indicated formation of single phase distorted R3c structure. Microstructural investigation using the field emission scanning electron microscope (FESEM) showed that addition of Ta dramatically reduced the average grain size of Bi0.8La0.2FeO3 due to its strong pinning effect from 10.6 μm in Bi0.8La0.2FeO3 to 0.92 μm in Bi0.8La0.2Fe0.95Ta0.05O3. Ta doped BLFO showed superior values of dielectric constant (>2000) at room temperature. At higher temperature a considerable increase in the dielectric constant of Bi0.8La0.2FeO3 samples occurred due to space charge polarization. However, in Ta-substituted ceramics the stability of dielectric constant with temperature considerably improved. DTA analysis revealed that the peak for ferroelectric transition (TC) shifted towards higher temperatures for the Ta-substituted BLFO and reached 870 °C for x = 0.05. Moreover, a significant increase in remanent magnetization has been observed with increasing Ta addition in BLFO samples from 0.038 emu g−1 in Bi0.8La0.2FeO3 to 1.13 emu g−1 in Bi0.8La0.2Fe0.95Ta0.05O3.