The present report leads to the development of a lead-free perovskite system (BaCa)(Sn0.11Zr0.05Ti0.84)O3 (BCSZTx); 00.20, exhibiting relaxor ferroelectric behaviour in an average cubic structure. The x-ray diffraction measurements have shown a simple cubic phase with Pmm space group for all the compositions. Despite having a centrosymmetric cubic phase, a slim hysteresis loop has been observed via PE loop measurements. Raman spectroscopic measurements have revealed the presence of local ordering in the macroscopic cubic matrix, corresponding to ‘A’ and ‘B’ sites. The cooperative behaviour of ‘A’ and ‘B’ site off-centered (local) atoms leading to microscopic polar symmetry in the macroscopically cubic matrix is held responsible for the observed relaxor ferroelectric nature. Owing to the aforementioned contrapositive behaviour, these ceramics have exhibited a high value of dielectric constant. Eventually, we have clearly observed a decisive role of Ca2+ dopant at ‘A’ site in BCSZTx ceramic system leading to the enhancement in the relaxor ferroelectric behaviour and dielectric properties. The presence of a slim hysteresis loop along with broad and diffuse dielectric nature makes these ceramics, a potential candidate for energy storage applications.

The effect of 5% Sr substitution at the Ba site in Ba(Ti1−xSnx)O3 (BTSnx) system is investigated for x = 0.05, 0.075, and 0.12 compositions. The phase transition studies were carried out using dielectric, high-resolution X-ray diffraction, and PE hysteresis loop measurements. Rietveld refinements, along with dielectric studies on strontium-doped BTSnx reveal that the interferroelectric phase boundaries observed in pure BaTiO3 approach the Tc line, with morphotropic phase boundary like behaviour. The PE hysteresis loops show enhanced polarization (≈190%) in Sr-doped BTSn5, which is attributed to the inter-ferroelectric phase instability (which facilitates polarization rotation, phase boundary motion, and domain wall motion), enhanced tetragonality (c/a), and increased unit-cell polarization evident from the amplitude of frozen phonon mode (GM − 4) corresponding to the zone center of the cubic Brillouin zone. The ferroelectric polarization observed in the average-cubic-structure state of Sr-doped BTSn12 is attributed to the cooperative polar off-centre displacements of A (Ba 2+ /Sr 2+ ) and B (Ti 4+ /Sn 4+ ) site cations along 100 and 111 directions, respectively. Further, Sr-doped BTSn12 has high dielectric constant and low loss which makes this material an important composition for various technological applications.

We report here the presence of three coexisting ferroelectric phases in a lead-free lithium sodium niobate (Lix Na1−xNbO3; LNNx) system stable for 0.15≤x≤0.80, which contrasts the review report of Dixon and Lightfoot [Phys. Rev. B 97, 224105 (2018)]. More importantly, we have identified LNN20 as an important composition for technological applications due to its high dielectric permittivity, low loss, and high ferroelectric response. The anomalous dielectric and ferroelectric responses in LNN20 have been attributed to the morphotropic phase boundary like nature around this composition.

Various distortion parameters for alkaline-earth-metal-based perovskites (A 2+ B 4+O3) have been analyzed as a function of A- and B-site cationic radii R A and R B . The observed octahedral rotations and their associated mode amplitudes have shown an increasing trend with larger B-site cations, while a decreasing trend has been observed with larger A-site cations. Moreover, the analysis demonstrates that for incipient ferroelectrics like CaTiO3 and SrTiO3, having respective space groups Pnma (a − 0 b + 0 a − 0) and Pm 3 m (a 0 0 a 0 0 a 0 0), ferroelectric displacements are achieved via cation manipulation, which is governed by the R A /R B parameter. The increase in R A /R B through substitutions on the A site may suppress octahedral rotations as well as A-site anti-polar displacements in CaTiO3 and can consequently lead to a ferroelectrically distorted BaTiO3-like P4mm (a 0 0 a 0 0 c 0 +) phase via a cubic phase of SrTiO3, which has an intermediate R A /R B parameter. These results have been further corroborated by the calculated amplitudes of various frozen phonon modes associated with the cubic Pm 3 m Brillouin zone, responsible for symmetry breaking to tilt-oriented non-ferroelectric Pnma and ferroelectric P4mm phases.

We report here the role of component freezing of three dimensional polar (Γ4-) phonon mode corresponding to the center of cubic Brillouin zone in tuning the structure-property correlations of a scientifically enriched and technologically important barium titanate based eco-friendly functional material (Ba0.92Ca0.08)(Zr0.05Ti0.95-xSnx)O3; BCZTSnx (0 ≤ x ≤ 0.10) synthesized via solid-state reaction method. The combined X-ray diffraction, Raman spectroscopic analysis, and temperature-dependent dielectric studies have revealed the presence of several crystallographic phase transitions with coexisting phases viz., P4mm→(P4mm + Amm2 + R3m)→(Amm2 + R3m)→R3m→(Pm3m+R3m), as a function of Sn(x) content. These crystallographic phases viz; P4mm, Amm2, and R3m results due to freezing of the component(s) of Γ4- phonon mode (belonging to Pm3m space group), with the respective order parameter directions (0,0,a), (a,a,0), and (a,a,a) leading to ferroelectric polarization along ⟨001⟩, ⟨110⟩ and ⟨111⟩ directions, respectively. The ceramic composition corresponding to x=0.025 exhibits a significant reduction in the coercive field (Ec) and an enhancement in ferroelectric polarization (Pr) in comparison to x=0, inferred from PE loop measurements. The enhancement in ferroelectric polarization at x=0.025 has been attributed to the inter-ferroelectric threephase (P4mm + Amm2 + R3m) coexistence around this composition, and significantly enhanced amplitudes of ferroelectric phonon modes corresponding to orthorhombic and rhombohedral phases, calculated using the symmetry mode analysis technique. The existence of a high ferroelectric polarization and low coercive field may lead to x=0.025 composition as an eco-friendly candidate for ferroelectric memory devices.