Structural and ferroelectric properties of Ta-substituted Bi 0.8 La 0.2 FeO 3 multiferroics Takian Fakhrul 1 , Rubayyat Mahbub 2 , Nadim Chowdhury 3 , Quazi Khosru 3 and Ahmed Sharif 1 1 Department of Materials and Metallurgical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh. 2 Department of Glass and Ceramic Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh. 3 Department of Electrical and Electronic Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh. Corresponding Author: Dr. Ahmed Sharif, Tel: (+88)-01912802486, Fax: (+88)-029665618, E-mail: "Dr. Ahmed Sharif" asharif@mme.buet.ac.bd Abstract The role of doping Ta in Fe-site on the phase, microstructure and dielectric properties of Bi 0.8 La 0.2 FeO 3 (BLFO) has been investigated in this research. Single phase Bi 0.8 La 0.2 Fe 1- x Ta x O 3 (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 o C for 2 hours and then sintered at 1000 o C for 2 hours. 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 Bi 0.8 La 0.2 FeO 3 due to its strong pinning effect from 10.6 µm in Bi 0.8 La 0.2 FeO 3 to 0.92µm in Bi 0.8 La 0.2 Fe 0.95 Ta 0.05 O 3. Ta doped BLFO showed superior values of dielectric constant (> 2000) at room temperature. At higher temperature a considerable increase in the dielectric constant of Bi 0.8 La 0.2 FeO 3 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 (T C ) shifted towards higher temperatures for the Ta- substituted BLFO and reached 870 o C for x=0.05.