Abstract
Ferroelectrics are important technological materials with wide‐ranging applications in electronics, communication, health, and energy. While lead‐based ferroelectrics have remained the predominant mainstay of industry for decades, environmentally friendly lead‐free alternatives are limited due to relatively low Curie temperatures (T C) and/or high cost in many cases. Efforts have been made to enhance T C through strain engineering, often involving energy‐intensive and expensive fabrication of thin epitaxial films on lattice‐mismatched substrates. Here, a relatively simple and scalable sol–gel synthesis route to fabricate polycrystalline (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 nanowires within porous templates is presented, with an observed enhancement of T C up to ≈300 °C as compared to ≈90 °C in the bulk. By combining experiments and theoretical calculations, this effect is attributed to the volume reduction in the template‐grown nanowires that modifies the balance between different structural instabilities. The results offer a cost‐effective solution‐based approach for strain‐tuning in a promising lead‐free ferroelectric system, thus widening their current applicability.
Highlights
Ferroelectrics are important technological materials with wide-ranging appliattracted considerable attention,[2,3] due to confinement-induced enhancement of cations in electronics, communication, health, and energy
Ferroelectric materials have been widely investigated for decades the ferroelectric polarization and the piezoelectric responses as the building blocks for applications ranging from transducers from these materials
BCT-0.5BZT NWs were prepared through a two-step chemical synthesis process, shown schematically in Figure 1a that includes (i) preparation of the BCT-0.5BZT sol and subsequent infiltration of the sol in track-etched polyimide (PI) porous templates of pore diameter ≈200 nm and thickness ≈20 μm, and (ii) annealing the sol-filled PI template at 1000 °C in air to crystallize the BCT-0.5BZT ceramic phase
Summary
BCT-0.5BZT NWs were prepared through a two-step chemical synthesis process, shown schematically in Figure 1a that includes (i) preparation of the BCT-0.5BZT sol and subsequent infiltration of the sol in track-etched polyimide (PI) porous templates of pore diameter ≈200 nm and thickness ≈20 μm, and (ii) annealing the sol-filled PI template at 1000 °C in air to crystallize the BCT-0.5BZT ceramic phase. From the P–E measurements, the BCT-0.5BZT NWs showed clear hysteresis loops till 50 °C, polarization was found to increase with temperature indicating that at these temperatures, the material is not fully in a pure ferroelectric tetragonal phase, unlike what is expected in the bulk This is confirmed by dielectric permittivity measurements presented . While the first transition in the bulk sample (inset I in Figure 4a) was recorded below room temperature (≈18 °C) the second transition corresponding to a ferroelectric-to-paraelectric transition was recorded at about TC ≈ 90 °C, as predicted by the phase diagram of the BCT-0.5BZT composition,[19] BCT-0.5BZT NWs, showed two dielectric anomalies at ≈110 °C and ≈300 °C, indicating two distinct phase transitions (Figure 4b), with the second one being stronger These two peak temperatures correspond to rhombohedral–tetragonal (R–T) structural transition (as shown enlarged in inset II), and tetragonal–cubic (T–C) structural transition in BCT-0.5BZT NWs which were enhanced by ≈100 °C and >200 °C, for the R–T and T–C transitions respectively, as compared to the bulk and other reported values in the literature[19] (see Figure S9, Supporting Information). The BCT-0.5BZT NWs were found to have low loss factor in the entire temperature range of measurement, as shown in Figure 4d, values of which were comparable with other nanoferroelectric systems.[38,40] The observed low dielectric loss in our BCT-BZT NWs indicates that the measured hysteresis loops, as well as the dielectric peak anomaly at 300 °C, are not related to conductivity phenomena
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