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Lead‐based piezo‐ceramics like lead zirconate titanate (PZT) are a mainstay for many piezoelectric applications. However, lead oxide (PbO) evaporation during sintering poses a significant environmental challenge. Flash sintering (FS) is a novel technique that can densify ceramics in seconds and at a much lower furnace temperature. The liquid‐phase FS (LPFS) of PZT (Pb (Zr0.5Ti0.5) O3, with 3 wt.% Cu2O and PbO in the molar ratio of 1:4) is investigated in this work. Further, a comparison has been made among the lead loss, dielectric, and piezoelectric properties of flash‐sintered and conventionally liquid‐phase‐sintered PZT. It has been observed that the evaporation of PbO has been brought down 3–5 times by FS. The dielectric constant of LPFS PZT is significantly higher, especially at higher frequencies with lower dielectric loss. An enhanced piezoelectric coefficient in flash‐sintered PZT has also been observed. The LPFS of PZT shows that the lead loss can be brought down significantly with the added benefit of enhanced dielectric and piezoelectric properties. XRD and Rietveld analysis show an increase in tetragonality after FS in comparison with conventional sintering. XPS and ESR studies show a difference in defect concentration after FS in comparison with conventional sintering that is likely responsible for the enhanced dielectric and piezoelectric properties. [ABSTRACT FROM AUTHOR]

We study the magnetic properties and emergence of superconductivity in YBa$_2$Cu$_3$O$_7$ (YBCO)/ La$_{0.67}$Sr$_{0.33}$MnO$_3$ (LSMO) heterostructures. Bilayer films of superconducting layer, YBCO, and ferromagnetic layer, LSMO were grown on SrTiO$_{3}$ (STO) (001) substrate using ultrahigh vacuum Pulsed Laser Deposition system. Magnetization data at 100 K as a function of applied magnetic field shows ferromagnetic behaviour due to the LSMO layer. Cooling below 100 K leads to superconductivity in this material; the onset of superconductivity occurs at a temperature, $T_{c,SC},$ of 86 K for $H_{ext}\perp c$ (in-plane) \& 84 K for $H_{ext}||c$ (out-of-plane) under 100 Oe applied field. In-plane magnetic measurements show significant suppression of diamagnetic behaviour as compared to the out-of-plane measurements. The susceptibility signals are higher for out-of-plane direction. Such strong anisotropy in magnetism and the transition temperatures reveal complex interplay of magnetism and superconductivity in this system and calls for further study in this direction.

There is a growing interest in BiFeO3-based alloys because of the possibility it offers for developing high-temperature high-performance piezoelectric materials and for their interesting multiferroic properties. Often such ceramics are synthesized with additives either to reduce/suppress leakage current that the system inherits from the parent compound BiFeO3 or to promote sintering via formation of the liquid phase. We demonstrate here the propensity for stabilizing ferromagnetism in the ferroelectric solid solution BiFeO3–PbTiO3 (BF–PT) when synthesized with additive MnO2. Detailed investigation revealed that the ferromagnetic property of the ceramic is extrinsic and caused by the additive enabled precipitation of trace amount of the ferrimagnetic Pb-hexaferrite phase, not easily detected in conventional x-ray diffraction measurements. We also show that the ferromagnetic property is induced in Co-modified BF–PT. However, in this case, the additive stabilizes the CoFe2O4 spinel ferrite phase. While our findings offer a strategy to develop particulate magnetoelectric multiferroic composites using additive assisted precipitation of the ferrimagnetic phase(s) in BiFeO3-based ferroelectric alloys, it also helps in better understanding of the electromechanical response in BFO-based alloys. [ABSTRACT FROM AUTHOR]

One of the important requirements for piezoelectric materials for use as high strain actuators is that they exhibit large unipolar electrostrain with minimum hysteresis. While large unipolar electrostrain >1% is generally achievable in good quality single crystals, most polycrystalline piezoelectric show low values < 0.4%. Unipolar electrostrain 0.5%–0.7% in polycrystalline piezoelectrics has often been reported in Na0.5Bi0.5TiO3-based compositions at the non-ergodic ergodic boundary. Not amenable to poling, such materials exhibit almost nearly zero direct piezoelectric coefficient (d33 ∼ 0 pC/N) and cannot be simultaneously used as a sensor. In this paper, we report a combination of large unipolar electrostrain of ∼0.6% with small strain hysteresis of 25% in a Sn-modified relaxor ferroelectric system PbTiO3–Bi(Ni1/2Zr1/2)O3. It exhibits d33 ∼ 340 pC/N, which is stable up to 130 °C, and large signal converse piezoelectric coefficient d33* ∼ 1200 pm/V. A combination of large d33 and d33* in the same material makes it an important candidate for simultaneous use as a sensor and high strain actuators. X-ray diffraction study in situ with the electric field suggests that large electrostrain with low strain hysteresis in this system is because of the increased reversible switching of the field stabilized tetragonal ferroelastic domains. [ABSTRACT FROM AUTHOR]