Effects of BiMO₃ on dielectric, ferroelectric, and piezoelectric properties of perovskite lead‐free piezoelectric BaTiO₃–(Bi_0.5Na_0.5)TiO₃ ceramics

Abstract

New lead‐free piezoelectric ceramics of 0.9BaTiO3–(0.1−x)(Bi0.5Na0.5)TiO3–xBiMO3, M=Al and Ga, where x=0.00‐0.10, were fabricated by the solid‐state reaction technique. The effect of BiMO3 contents on the perovskite structure, phase transition, and dielectric, ferroelectric, and piezoelectric properties was investigated. X‐ray diffraction patterns showed that the ceramics exhibit a monophasic perovskite phase up to x=0.06, suggesting stabilized perovskite structures with B‐site aliovalent substitutions. Compositional‐dependent phase transitions were observed from tetragonal to pseudo‐cubic phase with increasing BiMO3 amounts. Al3+ ions were found to stabilize the transition temperature of the ceramics, while significantly decreasing transition temperature, and a change in the dielectric peak were found with an increasing amount of Ga3+. Regarding Al3+ substitution, the remanent polarization (Pr) values were found to decrease slightly with the Al3+ amount. With regard to Ga3+ substitution, Pr values decreased with the Ga3+ amount up to 0.06 and then increased slightly. The ceramics became softer with a higher degree of substitution according to the lower coercive field (Ec), when compared with 0.9BaTiO3–0.1(Bi0.5Na0.5)TiO3 ceramics. Ceramics with a lower degree of substitution and tetragonal phase showed butterfly strain loops that correlated with normal ferroelectric behavior.

Temperature Stable Dielectric Properties in BaTiO3–Bi(Mg2/3Nb1/3)O3–NaNbO3 Solid Solution

“…x T m (°C) ε r(max) ε r(RT) ε r(mid)250°C T À range (°C) for ε r � 15% (1 kHz) tanδ (RT) T À range (°C) for tanδ < 0.05 (1 kHz) P max (μC/cm 2 ) J rec (J/cm 3 ) 0 [12] lattice order due to occupancy of multiple cation at A-site (Ba 2 + , Bi 3 + , Na + ) and B-site (Ti 4 + , Mg 2 + , Nb 5 + ). [31] Therefore, by increasing the level of doping may further promote the short range ferroelectric order as previously reported for BaTiO 3 À NaNbO 3 , causing a decrease in ε r . [32] The maximum relative permittivity is found for the composition at x = 0.10 i. e. ε r = 495 and low dielectric loss at room temperature i. e. less than 0.003 at 1 kHz.…”

“…On the other hand, the incorporation of NN in BMN also change the charge disorder due to the different oxidation state of Na + than other A‐site cations. This may cause an increase in the degree of lattice order due to occupancy of multiple cation at A–site (Ba 2+ , Bi 3+ , Na + ) and B‐site (Ti 4+ , Mg 2+ , Nb 5+ ) . Therefore, by increasing the level of doping may further promote the short range ferroelectric order as previously reported for BaTiO 3 −NaNbO 3 , causing a decrease in ϵ r .…”

Enhanced photovoltaic performance via polarization in Bi/Co co‐doped KN‐based ferroelectric ceramics

“…However, ABO 3 -type perovskite ferroelectric materials have a large electronegativity difference between the B-site cation and the O-ion, resulting a wide bandgap (≥3.0 eV) in most ferroelectrics. [11][12][13] This condition makes the absorption of sunlight by ferroelectrics stay in the UV region, although BiFeO 3 , 14,15 which has a known bandgap of as low as 2.7 eV, can only absorb ∼20% of the solar spectrum. The absorption of sunlight by ferroelectrics needs to be improved to enhance its photoelectric conversion efficiency and photovoltaic output.…”

“…Ferroelectric photovoltaic materials with both bulk photovoltaic effect 9 and electrostatic potential at the nano‐domain wall, 10 which can generate photovoltaic voltages above the bandgap, can further improve the photovoltaic conversion efficiency and are potential candidates for next‐generation photovoltaic devices. However, ABO 3 ‐type perovskite ferroelectric materials have a large electronegativity difference between the B‐site cation and the O‐ion, resulting a wide bandgap (≥3.0 eV) in most ferroelectrics 11–13 . This condition makes the absorption of sunlight by ferroelectrics stay in the UV region, although BiFeO 3 , 14,15 which has a known bandgap of as low as 2.7 eV, can only absorb ∼20% of the solar spectrum.…”