Lead‐Free Polycrystalline Ferroelectric Nanowires with Enhanced Curie Temperature

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 (Ba 0.85 Ca 0.15 )(Zr 0.1 Ti 0.9 )O 3 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.

Tunable Ferroelectricity in Ruddlesden–Popper Halide Perovskites

“…Such a P−E loop shape has also been widely observed in various ferroelectric reports. 23,50,51 Finally, we performed MD simulations in a bid to gain deeper insights into the polarization switching behavior in these RP perovskites. Unlike the pure 2D perovskite (i.e., n ̅ = 1), which only consists of the weakly polar PEA molecule, the polarity of n ̅ = 2 to n ̅ = 5 can be enhanced by the highly polar MA + molecule (2.3 Debye).…”

Mapping piezoelectric response in nanomaterials using a dedicated non-destructive scanning probe technique

“…In addition, we observed that no NWs were dislodged or damaged in ND-PFM, whereas this was not strictly the case for c-PFM. In a recent work from our group, we studied the ferroelectric and dielectric properties of lead-free polycrystalline BCT-BZT NW network which was interestingly found to have an enhanced Curie temperature 25 . However, we were unable to image this NW network using c-PFM, which is an otherwise routine characterization technique for ferroelectric thin films.…”

“…However, we were unable to image this NW network using c-PFM, which is an otherwise routine characterization technique for ferroelectric thin films. We found that the NW network could not sustain the pressure induced by contact-mode AFM operation (see Supporting Information Figure S5a), and we only managed to perform and report single-point spectroscopy measurements, without correlation to topography 25 . Several other reports also present topography images accompanied by single point spectroscopy data when studying non-planar ferroelectric materials 37,38 , highlighting a key deficiency in the applicability of c-PFM to nanoscale objects in particular.…”

“…In order to circumvent this problem, we have developed a "non-destructive" PFM (ND-PFM) technique that allows spatially resolved piezoelectric properties of nanomaterials to be directly measured. We demonstrate the versatility of our method in addressing a wide range of piezoelectric nanomaterials by applying it to both polymeric as well as ceramic nanowires 24,25 which are otherwise destroyed or dislodged when using conventional PFM.…”

All-Mechanical Polarization Control and Anomalous (Electro)Mechanical Responses in Ferroelectric Nanowires

“…Piezoelectric and ferroelectric nanowires often exhibit properties that are not accessible in bulk. Some examples include anomalous coupling of light into the ferroelectric nanowire, enhanced Curie temperature, hardening of the soft modes, enhanced energy conversion and storage, unusual phase transitions, phases, and morphotropic phase boundary …”