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Pseudo-tetragonal phase boundary existent Ca0.60(Li0.5Bi0.5)0.40Bi2Nb2O9:xwt%MnO2 (CBNL:xMn) ceramic series is fabricated to investigate the ferroelectric and piezoelectric properties. Pure CBNL and CBNL:xMn ceramics have maintained their pseudo-tetragonal phase boundary even after the insertion of Mn ions. The addition of MnO2 in CBNL has improved the multifunctional properties of material at x = 0.20. CBNL:0.20Mn has shown the relative density of 98%, saturated polarisation (PS) of ~ 13.5 µC/cm2, high piezoelectric coefficient (d33) of ~ 25 pC/N, and high impedance of ~ 8.9 × 108 Ω at room temperature, which are the much improved values as compared to pure CBN or CBNL ceramics. The dielectric constant (ɛr) dependence on temperature is presenting the sharp peak of CBNL:0.20Mn ceramic at Curie temperature (TC) ~ 918°C confirming the strong ferroelectric nature of the ceramic. Importantly, poled CBNL:0.20Mn ceramic has shown the thermally stable depoling performance, which remains 92% (23 pC/N) of its initial room temperature value even after annealing the sample at 800°C. Results indicate the clear significance that the introduction of multivalence Mn ions in the pseudo-tetragonal existent region of CBNL has improved the multifunctional properties of the material, making it a strong candidate to be utilised in actuators and high-temperature piezoelectric devices. [ABSTRACT FROM AUTHOR]

Morphotropic phased boundary (MPB) existent Bi 0.5 (K 0.2 Na 0.8) 0.5 TiO 3 :xwt%MnO 2 (BKNT:xMn) ceramic system is fabricated to investigate the ferroelectric and piezoelectric properties. All the ceramic samples have maintained the tetragonal (P4mm)-rhombohedral (R3c) structural duality due to MPB regional investigation of BKNT. The addition of MnO 2 in BKNT has improved the multifunctional properties of the material at x ​= ​0.15. BKNT:0.15Mn ceramic has shown the maximum density of 6.98 ​g/cm3, remnant polarization (P r) ​∼ ​32.5 ​μC/cm2, high impedance of ∼108 ​Ω, d 33 of 206 ​pC/N, which are much improved properties than pure single phase BKNT and Bi 0.5 K 0.5 TiO 3 ceramics. The dependence of dielectric constant (ε r) on temperature suggests the relaxor behavior and the high Curie temperature (T C) ​∼ ​410 ​°C for BKNT:0.15Mn ceramic, higher than the T C ​∼ ​360 ​°C of pure BKNT ceramic. The poled ceramics have maintained the stable piezoelectric properties till 300 ​°C. The introduction of multivalence Mn has improved the multifunctional properties of the material significantly, making it a strong candidate to be utilized in actuators and sensors. [Display omitted] • Morphotropic phased boundary (MPB) existent Bi 0.5 (K 0.2 Na 0.8) 0.5 TiO 3 :xwt%MnO 2 (BKNT:xMn) ceramic system is fabricated. • All the ceramic samples have maintained the tetragonal (P4mm)-rhombohedral (R3c) structural duality due to MPB regional investigation of BKNT even after the addition of xwt%MnO 2. • BKNT:0.15Mn ceramic has shown the maximum density of 6.98 ​g/cm3, and remnant Polarization of P r ∼32.5 ​μC/cm2. • BKNT:0.15Mn has shown high impedance of ∼108 ​Ω and d 33 of 206 ​pC/N, which are much improved from the properties of pure Bi 0.5 K 0.5 TiO 3 ceramic. • The relaxor behavior and the high Curie temperature (T C) of ∼410 ​°C has been observed for BKNT:0.15Mn ceramics. [ABSTRACT FROM AUTHOR]