Eco‐friendly 0.92(Na0.5Bi0.49Nd0.01TiO3)‐0.08(BaTiO3) [denoted as NBNT‐BT 92/8] ceramic is synthesized with the help of conventional solid state reaction route. The structural phase pure studies reveals, the compound stabilizes into mixed phase of Cc + P4 mm and the surface morphology of microstructure shows the uniform distribution of Nd. The temperature dependent dielectric study reveals two typical anomalies with the diffuse phase transition and show the relaxor future estimated with the help of diffusivity (γ). From the temperature dependent polarization and room temperature bipolar strain hysteresis loops over broad electrical field range from (0–73) kV cm−1, the estimated energy storage density, energy storage efficiency, and strain values are Wrec ≈ 1.53J cm−3, η ≈ 93(%), and S(%) ≈ 0.4, respectively, which is the best obtained value among available various reported lead‐free piezoelectric ceramics. The adiabatic or electrocaloric temperature change (ΔT) is calculated to be ΔT ≈ 0.95 K at 50 kV cm−1. The obtained valued of ΔT, strain and energy storage density for NBNT‐BT 92/8 is tremendous enhancement compared with absence of Nd in NBT‐BT 92/8.

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Lead-free polycrystalline K 1/2 Bi 1/2 TiO 3 was prepared by the solid state reaction method. Experimentally observed frequencies of Raman modes signified its tetragonal phase, and matched reasonably well with theoretically calculated values. The relaxor nature of this material was observed in the temperature-dependent real part of the permittivity and dielectric loss curve. The value of the degree of diffuseness (1.99) was estimated from the modified Curie-Weiss law confirmed its relaxor behavior. The validation of this behavior was justified by the Vogel-Fülcher relation. The shoulder in the imaginary part of the modulus (M″) and permittivity (ε″) spectra revealed the presence of polar nano regions (PNRs). The evidence of PNRs was detectable above freezing temperatures, and became weaker when the temperature exceeded T m (temperature at the maximum of the dielectric constant). The electric fieldinduced polarization and strain curve showed the stabilization of the long-range ferroelectric order of the specimen at room temperature. Moreover, the discharge energy density and strain were 0.46 J cm −3 and 0.12%, respectively, at the maximum application of the electric field of 115 kV cm −1 at room temperature.

First-principles density functional calculations are performed to investigate the lattice dynamics, Infrared reflectivity, and Raman intensity spectra of a lead-free ferroelectric K 1/2 Bi 1/2 TiO 3 system. In particular, the A-site cation ordering in K 1/2 Bi 1/2 TiO 3 and its effects on lattice dynamics and the Raman spectrum are explored. The results suggest that the cation ordering at the A-site in K 1/2 Bi 1/2 TiO 3 significantly influences its Raman spectra. From the analysis of theoretical and experimental Raman spectra, it is suggested that randomly arranged cation ordered nanoregions with different A-site orderings are formed in K 1/2 Bi 1/2 TiO 3 samples. The random arrangement is favored by entropy contributions to free energy and may explain the lack of observed long-range A-site cation ordering in K 1/2 Bi 1/2 TiO 3. Further, it is suggested that partial A-site cation ordering may also occur in K 1/2 Bi 1/2 TiO 3 favored by kinetic factors during sample preparation. The Born effective charges of K and Bi ions at the A-site are computed and found to be significantly disparate, thereby suggesting hetero-polar activity at the A-site in K 1/2 Bi 1/2 TiO 3. The formation of A-site hetero-polar cation ordered nanoregions and their random or/and partially ordered arrangement in K 1/2 Bi 1/2 TiO 3 may play an important role in the determination of its relaxor properties apart from the dominant role played by polar nanoregions. The computed Infrared reflectivity and Raman intensity spectra are expected to provide benchmark first-principles results for further analysis of experimental spectra and results.

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