Reversible Phase Transformation Research Articles

Reversible phase transformations between Pb nanocrystals and a viscous liquid-like phase.

Phase transformations have been a prominent topic of study for both fundamental and applied science. Solid-liquid reaction-induced phase transformations can be hard to characterize, and the transformation mechanisms are often not fully understood. Here, we report reversible phase transformations between a metal (Pb) nanocrystal and a viscous liquid-like phase unveiled by in situ liquid cell transmission electron microscopy. The reversible phase transformations are obtained by modulating the electron current density (between 1000 and 3000 electrons Å-2 s-1). The metal-organic viscous liquid-like phase exhibits short-range ordering with a preferred Pb-Pb distance of 0.5 nm. Assisted by density functional theory and molecular dynamics calculations, we show that the viscous liquid-like phase results from the reactions of Pb with the CH3O fragments from the triethylene glycol solution under electron beam irradiation. Such reversible phase transformations may find broad implementations.

Origins of functional fatigue and reversible transformation of precipitates in NiTi shape memory alloy

The work clarifies several key questions in shape memory research that have eluded previous studies. The findings show that dislocation slip emanates at austenite-martensite interfaces during unloading and aligns with the internal twin boundary interface of martensite. It was observed that the type II internal twins of the martensite become parallel dislocations in the austenite. During reloading, these dislocations act as nucleation sites for the martensitic twins, reducing the nucleation barrier and the transformation stress. The precipitates facilitate martensite nucleation but also act as an obstacle to martensite front motion, restrict detwinning, and pin the interfacial dislocations during unloading, thereby contributing to residual strains and martensite stabilization. Martensite nucleation is not suppressed by the size of the thin film, which is of the order of 85 to 105 nanometers thick, and repeated transformation occurred cycle after cycle. Single crystals deformed in the <101>LD exhibited the best recoverability of up to 5.5 % and tensile stresses of up to 1.4 GPa. It was demonstrated for the first time that, when favorably oriented, Ni4Ti3 precipitates undergo a reversible phase transformation to R-phase and can accommodate up to 4 % reversible strains.

Thermomechanics of phase transformation induced localization in NiTi tubes. Part II constitutive modeling and simulations

In an isobaric test, typically used for establishing the transformation temperatures of SMAs, a specimen is taken through a cool/heat cycle at a prescribed stress level. The companion paper, Part I, demonstrated that such tests on NiTi tubes result in rather complex interactions between the helical bands of localized deformation induced by phase transformations, the associated latent heat, and the thermal exchange with the environment. These interactions were quantified using accurately controlled testing conditions and full-field diagnostics, and provide a challenging platform for evaluating analyses. In Part II this challenge is met by first extending the thermomechanical constitutive framework developed by our group to include variations of transformation stress, strain, and latent heat with temperature. Unique features of the model include: modeling the reversible phase transformations of NiTi through a single surface in the deviatoric stress–temperature space with the transformation strain and entropy as the internal variables; and use of softening to model the inhomogeneous deformation exhibited in tension. The model is calibrated to the isothermal results of Part I. The constitutive model is then incorporated into a fully coupled static displacement-thermally transient finite element analysis that is used to simulate the isobaric experiments on NiTi tubes of Part I over a range of stresses. The clamped ends of the experiment are idealized as radial constraints. Heat exchange between the structure and the environment is strictly by convection. Isobaric testing is simulated by taking the model tube through the cool/heat cycle of the experiment at the prescribed stress level. A small thickness depression at one of the ends is used to initiate localized transformation. The temperature-strain response is reproduced with the two transformations initiating at essentially the same temperatures as in the experiments, producing the correct transformation strains for all stress levels. Transformation of M propagates via a helical band at similar speeds as in the experiments, while transformation of A is via multipronged fronts for all cases. Successful reproduction of the velocities of the banded transformations is governed by the value of the convection coefficient. Overall, the reproduction of the isobaric experiments over a range of stress levels, validates the constitutive and structural models. It also points to the limitations of modeling the heat exchange between the specimen and the environment only by convection.

Hyper‐Elastic Deformation via Martensitic Phase Transformation in Cadmium Telluride

Cadmium telluride (CdTe) is a highly promising material for photovoltaics (PV) and photodetectors due to its light‐absorbing properties. However, efficient design and use of flexible devices require a deep understanding of its atomic‐level deformation mechanism. Herein, uniaxial compression deformation of CdTe monocrystalline with varying crystal orientations is investigated using molecular dynamics (MD) with a newly developed machine‐learning force field (ML‐FF), alongside in‐situ micropillar compression experiments. The findings reveal that CdTe bulk deformation is dominated by reversible martensitic phase transformation, whereas CdTe pillar deformation is primarily driven by dislocation nucleation and movement. CdTe monocrystals possess exceptional super‐recoverable deformation along the &lt;100&gt; orientation due to hyper‐elastic processes induced by martensitic transformation. This discovery not only sheds light on the peculiarities observed in micropillar experimental measurements, but also provides pivotal insights into the fundamental deformation behaviors of CdTe and similar II–VI compounds under various stress conditions. These insights are crucial for the innovative design and enhanced functionality of future flexible electronic devices.

Microstructure and Magnetic Properties of Fe67.6-Pd32-In0.4 (at.%) Shape Memory Melt-Spun Ribbons.

Fe-~30 at.%Pd is a ferromagnetic shape memory alloy (SMA) with a reversible thermoelastic fcc-fct phase transformation. The advantage of adding a small amount of Indium to Fe-Pd SMAs is, among other things, the upward shift of the transformation temperatures, which allows us to maintain the material in the martensitic state (fct structure) at room temperature. In this work, we study the microstructure and the magnetic properties of nominally Fe67.6-Pd32-In0.4 (at.%) melt-spun ribbons. Energy-dispersive spectroscopy analysis showed a certain level of non-uniformity of Indium distribution in the as-spun ribbon. However, the attempt to homogenize the ribbon by annealing at 1273 K for 120 h resulted in an unfavoured structural change to bct martensite. Magneto strains induced by a 9 kOe magnetic field reached over 400 ppm for certain field orientations, which is around four times more than the magneto strains of near-binary Fe-Pd shape memory alloys.

In situ atomic-scale tracking of unusual interface reaction circulation and phase reversibility in (de)potassiated alloy-typed anode

Alloy-typed anode materials, endowed innately with high theoretical specific capacity, hold great promise as an alternative to intercalation-typed counterparts for alkali-ion batteries. Despite tremendous efforts devoted to addressing drastic volume change and severe pulverization issues of such anodes, the underlying mechanisms involving dynamic phase evolutions and reaction kinetics have not yet been fully comprehended. Herein, taking antimony (Sb) anode as a representative paradigm, its microscopic operating mechanisms down to the atomic scale during live (de)potassiation cycling are systematically unraveled using in situ transmission electron microscopy. Highly reversible phase transformations at single-particle level, that are Sb ↔ KSb2 ↔ KSb ↔ K5Sb4 ↔ K3Sb, were revealed during cycling. Meanwhile, multiple phase interfaces associated with different reaction kinetics coexisted and this phenomenon was properly elucidated in the context of density functional theory calculations. Impressively, previously unexplored unidirectional circulation of reaction interfaces within individual Sb particle is confirmed for both potassiation and depotassiation. Based on the empirical results, the surface diffusion-mediated potassiation-depotassiation pathways at single-particle level are suggested. This work affords new insights into energy storage mechanisms of Sb anode and valuable guidance for targeted optimization of alloy-typed anodes (not limited to Sb) toward advanced potassium-ion batteries.

Design, synthesis and characterization of multilayer environmental barrier coatings

The formation of cristobalite thermally grown oxides (TGO) is a major life limiting factor for environmental barrier coatings (EBCs) with Si bond coat exposed to high temperature steam environments due to its reversible phase transformation and the resultant cracking behaviour during thermal cycling. Therefore, controlling or avoiding cristobalite TGO formation by engineering coating chemistry and architecture will be desirable for a highly durable EBC system. In this work, a multilayer Si/Al-Si-N/Yb2Si2O7 EBC was produced using a hybrid vapor deposition process. The oxidation behavior of the EBC was evaluated in flowing 90% H2O (g) + 10% air at 1316 °C. After 100 h and 510 h steam test, crack-free mullite and Al-Si-O-N layers formed above Al-Si-N layer and no SiO2 scale formation of Si bond coat was observed. Detailed TEM analyses show that the Al-Si-N layer successfully prevented the oxidation of underlying Si bond coat and avoided the formation of detrimental cristobalite phase.

Designing a Morphing Wing for Fixed-Wing UAVs By IJISRT

This project report details the original conceptualization, design, and analysis of a morphing wing structure for fixed-wing Unmanned Aerial Vehicles (UAVs). Our approach incorporates an octahedron cell structure coupled with the application of shape memory alloys(SMAs) to facilitate controlled wing morphing. The primary goal is to augment the UAVs aerodynamic efficiency and adaptability to various flight conditions. The octahedron cell structure is employed as the foundational framework, providing a balance between structural integrity andflexibility for shape adjustments. The integration of shape memory alloys, known for their reversible phase transformations, enables precise and efficient control over the morphing process. Through this combination, we aim to optimize the UAVs flight characteristics, including improved efficiency, stability, and maneuver ability. To validate the feasibility and performance of the morphing wing design, Finite Element Analysis (FEA) has been conducted. This computational approach allows for a comprehensive evaluation of the structural integrity and aerodynamic behavior of the morphing wing under diverse loading conditions. The FEAresults offer crucial insights into the structural response, stress distribution, and deformation patterns, guiding the iterative refinement of the design for optimal functionality. This project represents a unique contribution to UAV technology, presenting an original perspective on morphing wing design that harnesses the benefits of octahedron cell structureand shape memory alloys. The insights gained from the FEA analysis provide valuable guidance for the ongoing development and implementation of morphing wing structures in fixed- wing UAVs. This work sets the stage for improved adaptability and performance in a range of operational scenarios, without reliance on external sources or existing research

Layered Chalcogenide Scintillators Enabled by Reversible Hydrous-Induced Phase Transformation for High-Resolution X-ray Imaging.

Scintillation materials have been widely used in various fields, such as medical diagnosis and industrial detection. Chalcogenides have the potential to become a new generation of high-performance scintillation materials due to their high effective atomic number and good resistance to radiation damage. However, research on their application in radiation detection is currently very scarce. Herein, single crystals of rare earth ion-doped ternary chalcogenides NaGaS2/Eu were grown by a high-temperature solid-phase method. It exhibits unique characteristics of structure transformation by absorbing water molecules from the air. To maintain the anhydrous phase of the material, we have used a strategy of organic-inorganic composites of epoxy resin and NaGaS2/Eu to prepare devices for radiation detection and discuss the irradiation luminescence properties of the two phases. The anhydrous phase of NaGaS2/Eu demonstrates excellent sensitivity to X-rays, with a low detection limit of 250 nGy s-1, which is approximately 1/22 of the medical imaging dose. Additionally, composite flexible films were prepared, which exhibited excellent performance in X-ray imaging. These films enable clear observation of a wide range of objects with a high spatial resolution of up to 13.2 line pairs per millimeter (lp mm-1), indicating that chalcogenide holds promising prospects in the realm of X-ray imaging applications.

High thermal stability effect of vanadium on the binary CuAl base alloy for a novel CuAlV high-temperature shape memory alloy

Abstract In this study, two high-temperature shape memory alloys (HTSMAs) of CuAlV with unprecedented chemical compositions were fabricated using the arc melting technique, followed by traditional ice-brine water quenching after the melting process. To characterize the shape memory properties and structure of the alloys, a series of tests including differential calorimetry (DSC and DTA), EDS, optical microscopy, and XRD were conducted. The DSC tests, performed at different heating and cooling rates, demonstrated highly stable reversible martensitic phase transformation peaks at high temperatures, which were also confirmed by the results of DTA tests. Microstructural XRD and optical microscopy tests were conducted at room temperature, revealing the martensitic structure of the alloys in both cases. Based on all the results, the effects of different minor amounts of vanadium additives directly on the CuAlV alloy were discussed.

Atomic-Scale In Situ Observations of Reversible Phase Transformation Assisted Twinning in a CrCoNi Medium-Entropy Alloy.

Twinning is an important deformation mode of face-centered-cubic (FCC) medium- and high-entropy alloys, especially under extreme loading conditions. However, the twinning mechanism in these alloys that have a low or even negative stacking fault energy remains debated. Here, we report atomic-scale in situ observations of the deformation process of a prototypical CrCoNi medium-entropy alloy under tension. We found that the parent FCC phase first transforms into a hexagonal close-packed (HCP) phase through Shockley partial dislocations slipping on the alternate {111} planes. Subsequently, the HCP phase rapidly changes to an FCC twin band. Such reversible phase transformation assisted twinning is greatly promoted by external tensile loads, as elucidated by geometric phase analysis. These results indicate the previously underestimated role of the metastable HCP phase in nanotwin nucleation and early plastic deformations of CrCoNi alloys and shed light on microstructure regulation of medium-entropy alloys with enhanced mechanical properties.

High-pressure phase transitions in a laser directed energy deposited Fe-33Cu Alloy

Additively manufactured Fe-Cu alloys contain both equilibrium face-centered cubic (FCC) and metastable body-centered cubic (BCC) crystal structure Cu precipitates depending on their size. However, the stability of these nanoscale precipitates under extreme conditions such as high pressures has not been reported. This study investigates the phase transformations and microstructural stability of laser directed energy deposition (DED-LB) made Fe67Cu33 alloy (nominal composition in at.%) under high static pressure deformation using in-situ synchrotron X-ray diffraction under pressure, postmortem high-resolution scanning transmission electron microscopy (HR-STEM), and molecular dynamics (MD) simulations. In-situ XRD results reveal a reversible phase transformation from BCC to the hexagonal close-packed (HCP) structure in the Fe grains at an onset pressure of 16.4 GPa, significantly higher than reported in the literature for pure Fe. Although no high-pressure phase transition was observed in the FCC Cu grains through XRD, HR-STEM analysis uncovers a phase transition to the HCP structure in nanoscale metastable BCC Cu precipitates within the BCC Fe matrix. After decompression, the Fe matrix reverted back to the BCC structure with periodic lath martensite, while regions of the nanoscale BCC Cu precipitates retained the metastable HCP structure. MD simulations support the BCC → HCP transition in the embedded nanoscale coherent Cu precipitates, consistent with the classical Burgers mechanism. Thus, by leveraging in-situ XRD observation, postmortem high-resolution S/TEM microscopy, and MD simulations, this study offers profound insights into the distinctive phase transformations induced by high pressure in DED-LB Fe67Cu33 alloy, which is distinguished by its hierarchical microstructure.

Preparation and thermophysical properties of medium-entropy fluorite-structured oxide of (Y0·25Zr0.25Hf0.25Ce0.25)O2−δ

A medium-entropy fluorite-structured ceramic of (Y0·25Zr0.25Hf0.25Ce0.25)O2−δ was prepared using a solid state reaction method combined with conventional sintering at 1600 °C for 10 h. This ceramic has uniform elemental distribution without impurity and segregation. The annealing experiment results show a reversible transformation between single phase and double phases in (Y0·25Zr0.25Hf0.25Ce0.25)O2−δ in 800–1600 °C. The reversible phase transformation does not display any obvious influence on the thermal expansion of this sample. The thermal expansion coefficient of (Y0·25Zr0.25Hf0.25Ce0.25)O2−δ is 12.4 × 10−6 K−1 in 100–1500 °C, higher than that of 8 wt% yttria-stabilized zirconia (8 YSZ). Furthermore, (Y0·25Zr0.25Hf0.25Ce0.25)O2−δ possesses a lower thermal conductivity (1.51 W m−1 K−1 at 900 °C) and higher oxygen barrier property compared with 8 YSZ at high temperature. The Vickers' hardness, Young's modulus and fracture toughness of (Y0·25Zr0.25Hf0.25Ce0.25)O2−δ are 10.0 GPa, 193.9 GPa and 1.93 MPa m1/2, respectively. These results demonstrate that (Y0·25Zr0.25Hf0.25Ce0.25)O2−δ can be used as a promising candidate ceramic of thermal barrier coatings.

Berkovich indentation and the Oliver-Pharr method for shape memory alloys

Advances in instrumentation and interpretation of nanoindentation data with the Oliver-Pharr (O-P) method have fueled the reliable assessment of hardness and elastic modulus. However, shape memory alloys (SMAs) undergo a reversible phase transformation that complicates and challenges the conventional practice. This paper examines through finite element simulations the variation in nanoindentation response with SMA constitutive properties and the deformation regimes underneath a Berkovich indenter. Unique features of phase transformations – including tension-compression asymmetry, limited magnitude of transformation strain compared to plastic strain, and pressure-dependent transformation stress – inject fundamentally different patterns of elastic and inelastic deformation, compared to conventional elastic-plastic indentation. This can generate errors of up to 16% and 40% in hardness and modulus, respectively, when a conventional O-P approach for elastic-plastic materials is used. These errors are decreased if (1) contact stiffness is measured over a reduced (2% or less) portion of the initial unloading response and (2) new material-dependent expressions are used for geometric and correction factors in the O-P nanoindentation analysis. Approximate analytic expressions are obtained for the effective elastic modulus and martensite volume fraction in the inhomogeneous medium created by indentation. This new method is applied to Ni50.5Ti49.5 (at%) wire and for other SMAs, general guidance for selection of geometric and correction factors is provided.

Self-terminating, heterogeneous solid–electrolyte interphase enables reversible Li–ether cointercalation in graphite anodes

Ether solvents are suitable for formulating solid-electrolyte interphase (SEI)-less ion-solvent cointercalation electrolytes in graphite for Na-ion and K-ion batteries. However, ether-based electrolytes have been historically perceived to cause exfoliation of graphite and cell failure in Li-ion batteries. In this study, we develop strategies to achieve reversible Li-solvent cointercalation in graphite through combining appropriate Li salts and ether solvents. Specifically, we design 1M LiBF4 1,2-dimethoxyethane (G1), which enables natural graphite to deliver ~91% initial Coulombic efficiency and >88% capacity retention after 400 cycles. We captured the spatial distribution of LiF at various length scales and quantified its heterogeneity. The electrolyte shows self-terminated reactivity on graphite edge planes and results in a grainy, fluorinated pseudo-SEI. The molecular origin of the pseudo-SEI is elucidated by ab initio molecular dynamics (AIMD) simulations. The operando synchrotron analyses further demonstrate the reversible and monotonous phase transformation of cointercalated graphite. Our findings demonstrate the feasibility of Li cointercalation chemistry in graphite for extreme-condition batteries. The work also paves the foundation for understanding and modulating the interphase generated by ether electrolytes in a broad range of electrodes and batteries.

Phase-field description of fracture in NiTi single crystals

A phase-field model for thermomechanically-induced fracture in NiTi at the single crystal level, i.e., fracture under loading paths that may take advantage of either of the functional properties of NiTi–superelasticity or shape memory effect–, is presented, formulated within the kinematically linear regime. The model accounts for reversible phase transformation from austenite to martensite habit plane variants and plastic deformation in the austenite phase. Transformation-induced plastic deformation is viewed as a mechanism for accommodation of the local deformation incompatibility at the austenite–martensite interfaces and is accounted for by introducing an interaction term in the free energy derived based on the Mori–Tanaka and Kröner micromechanical assumptions and the hypothesis of martensite instantaneous growth within austenite. Based on experimental observations suggesting that NiTi fractures in a stress-controlled manner, damage is assumed to be driven by the elastic energy, i.e., phase transformation and plastic deformation are assumed to contribute in crack formation and growth indirectly through stress redistribution. The model is restricted to quasistatic mechanical loading (no latent heat effects), thermal loading sufficiently slow with respect to the time rate of heat transfer by conduction (no thermal gradients), and a temperature range below Md, which is the temperature above which the austenite phase is stable, i.e., stress-induced martensitic transformation is suppressed. The numerical implementation of the model is based on an efficient scheme of viscous regularization in both phase transformation and plastic deformation, an explicit numerical integration via a tangent modulus method, and a staggered scheme for the coupling of the unknown fields. The model is shown able to capture transformation-induced toughening, i.e., stable crack advance attributed to the shielding effect of inelastic deformation left in the wake of the growing crack under nominal isothermal loading, actuation-induced fracture under a constant bias load, and crystallographic dependence on crack pattern.

Realizing reversible phase transformation of shape memory ceramics constrained in aluminum

Small-scale shape memory ceramics exhibit superior shape memory or superelasticity properties, while their integration into a matrix material and the subsequent attainment of their reversible tetragonal-monoclinic phase transformations remains a challenge. Here, cerium-doped zirconia (CZ) reinforced aluminum (Al) matrix composite is fabricated, and both macroscopic and microscopic mechanical tests reveal more than doubled compressive strength and energy absorbance of the composites as compared with pure Al. Full austenitization in the CZ single-crystal clusters is achieved when they are constrained by the Al matrix, and reversible martensitic transformation triggered by thermal or stress stimuli is observed in the composite micro-pillars without causing fracture in the composite. These results are interpreted by the strong geometric confinement offered by the Al matrix, the robust CZ/Al interface and the local three-dimensional particle network/force-chain configuration that effectively transfer mechanical loads, and the decent flowability of the matrix that accommodates the volume change during phase transformation.

Unlocking the Origins of Highly Reversible Lithium Storage and Stable Cycling in a Spinel High‐Entropy Oxide Anode for Lithium‐Ion Batteries

AbstractDeveloping high‐capacity conversion‐type anodes with superior durability substituting conventional graphite anodes is urgently desired to improve the energy density of lithium‐ion batteries (LIBs). However, fatal capacity decay during cycling of the conversion‐type anodes, which is primarily due to their inevitable structural degradation and continuous solid‐electrolyte interphase reformation induced by drastic volume change, has highly restricted their commercialization. And, the interrelated effects of phase transformation, structural evolution, and electrochemical characteristics of the conversion‐type anodes during cycling remain poorly understood. Herein, the findings on the fabrication and understanding of a previously unexplored entropy‐stabilized spinel oxide, (Co0.2Mn0.2V0.2Fe0.2Zn0.2)3O4 as a promising conversion anode for LIBs, exhibiting not only moderate volume change character but also highly reversible capacities of ≈900 mAh g−1 for 500 cycles at 0.2 A g−1 and ≈500 mAh g−1 for 2000 cycles at 3 A g−1, respectively, are reported. Evidenced by in situ transmission electron microscopy coupled with theoretical calculations, its underlying mechanism underpinning highly reversible Li storage is explicitly revealed, which originates from reversible phase transformation and domain reconstruction during cycling. Moreover, the origin of small volume change is also clearly clarified. This work provides renewed mechanistic insights into designing high‐capacity and durable conversion‐type electrode materials for high‐performance LIBs.

Switching Lead for Tin in PbHfO3: Noncubic Structure of SnHfO3**

AbstractThe removal of lead from commercialized perovskite‐oxide‐based piezoceramics has been a recent major topic in materials research owing to legislation in many countries. In this regard, Sn(II)‐perovskite oxides have garnered keen interest due to their predicted large spontaneous electric polarizations and isoelectronic nature for substitution of Pb(II) cations. However, they have not been considered synthesizable owing to their high metastability. Herein, the perovskite lead hafnate, i.e., PbHfO3 in space group Pbam, is shown to react with SnClF at a low temperature of 300 °C, and resulting in the first complete Sn(II)‐for‐Pb(II) substitution, i.e. SnHfO3. During this topotactic transformation, a high purity and crystallinity is conserved with Pbam symmetry, as confirmed by X‐ray and electron diffraction, elemental analysis, and 119Sn Mössbauer spectroscopy. In situ diffraction shows SnHfO3 also possesses reversible phase transformations and is potentially polar between ≈130–200 °C. This so‐called ‘de‐leadification’ is thus shown to represent a highly useful strategy to fully remove lead from perovskite‐oxide‐based piezoceramics and opening the door to new explorations of polar and antipolar Sn(II)‐oxide materials.

Switching Lead for Tin in PbHfO3 : Noncubic Structure of SnHfO3.

The removal of lead from commercialized perovskite-oxide-based piezoceramics has been a recent major topic in materials research owing to legislation in many countries. In this regard, Sn(II)-perovskite oxides have garnered keen interest due to their predicted large spontaneous electric polarizations and isoelectronic nature for substitution of Pb(II) cations. However, they have not been considered synthesizable owing to their high metastability. Herein, the perovskite lead hafnate, i.e., PbHfO3 in space group Pbam, is shown to react with SnClF at a low temperature of 300 °C, and resulting in the first complete Sn(II)-for-Pb(II) substitution, i.e. SnHfO3 . During this topotactic transformation, a high purity and crystallinity is conserved with Pbam symmetry, as confirmed by X-ray and electron diffraction, elemental analysis, and 119 Sn Mössbauer spectroscopy. In situ diffraction shows SnHfO3 also possesses reversible phase transformations and is potentially polar between ≈130-200 °C. This so-called 'de-leadification' is thus shown to represent a highly useful strategy to fully remove lead from perovskite-oxide-based piezoceramics and opening the door to new explorations of polar and antipolar Sn(II)-oxide materials.