Defect dipole induced improved electrocaloric effect in modified NBT-6BT lead-free ceramics

The Rietveld refinement of the polycrystalline powders 1% Fe and Mn-doped (Na0.5Bi0.5)0.94Ba0.06Ti0.98V0.02O3 at Ti-site confirmed a single rhombohedral (R3c) phase. bandgap, (Eg) was affected by anti-phase octahedral tilt angle spin-orbit splitting energy Ti4+2p3/2 Ti4+2p1/2 states. decrease in Bi loss increase binding Ba due to Fe/Mn doping has been correlated strengthening Bi-O Ba-O bonds which revealed from XPS studies thereby further related average A-O bond length structural studies. Hence, reduction oxygen vacancy (VO) for doped samples justified. A significant improvement dielectric constant, relaxation time (τ0), conductivity frequency-dependent (10 Hz-1 MHz) measurement study. conduction process are dominated short-range movement defects. activation (Ea ~1 eV) that there is presence double-ionized VOs. ECE study showed enhancement changes entropy, ΔS, adiabatic temperature difference, ΔT, doping, with ΔT being highest Fe-doped sample. Such properties mobility because formation(MnTi′′−Vo••)/(MnTi′−Vo••)• FeTi′′−Vo••/(FeTi′−Vo••)• defect dipoles.