Site engineering: A Tool to enhance functional properties in high-temperature lead-free relaxors prepared via air quenching

With employing judicious chemical modifications, two new isovalently substituted lead-free binary solid-solutions of 0.67BiFe
0.97-x
Ga
0.03
Sc
x
O
3
-0.33BaTiO
3
and 0.67(Bi
1-x
La
y
Fe
0.97
Ga
0.03
O
3
)-0.33(BaTiO
3
) abbreviated as BFSBT-x and BLFBT-y respectively where x, y ≤ 0.07 were synthesized via site engineering, using solid-state route employing air quenching sintering technique. Site engineering is used to introduce the functionality by substituting A/B sites in respective solid solutions of these perovskites (general formula ABO
3
). To better understand its effect, crystal structural, dielectric, optical, and ferroelectric properties were characterized and compared for different compositions. The X-ray diffraction pattern suggests the formation of pure perovskite structure with pseudocubic phase as the major phase present in both BFSBT-x and BLFBT-y series. The direct band gap energy of 1.97 eV and 2.14 eV lying in visible range was obtained for x=0.03 and y=0.03 composition, respectively. The temperature-dependent dielectric studies reveal frequency-dependent dielectric anomalies in permittivity corresponding to diffuse phase transitions stipulating relaxor-like behavior, which was further confirmed by modified Curie-Weiss law fitting. The enhanced temperature stability, good dielectric properties, and lower band gap suggest that site engineering is an efficient way to enhance the functional properties of BiFeO
3
-BaTiO
3
based samples for high-temperature applications.