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1. Strengthened relaxor behavior in (1− x )Pb(Fe _0.5 Nb _0.5 )O ₃ – x BiFeO ₃

   https://doi.org/10.1039/C9TC05883D  

   Prah, Uroš ; Dragomir, Mirela ; Rojac, Tadej ; Benčan, Andreja ; Broughton, Rachel ; Chung, Ching-Chang ; Jones, Jacob L. ; Sherbondy, Rachel ; Brennecka, Geoff ; Uršič, Hana ( March 2020 , Journal of Materials Chemistry C)

   A systematic study of (1− x )Pb(Fe 0.5 Nb 0.5 )O 3 – x BiFeO 3 ( x = 0–0.5) was performed by combining dielectric and electromechanical measurements with structural and microstructural characterization in order to investigate the strengthening of the relaxor properties when adding BiFeO 3 into Pb(Fe 0.5 Nb 0.5 )O 3 and forming a solid solution. Pb(Fe 0.5 Nb 0.5 )O 3 crystalizes in monoclinic symmetry exhibiting ferroelectric-like polarization versus electric field ( P–E ) hysteresis loop and sub-micron-sized ferroelectric domains. Adding BiFeO 3 to Pb(Fe 0.5 Nb 0.5 )O 3 favors a pseudocubic phase and a gradual strengthening of the relaxor behavior of the prepared ceramics. This is indicated by a broadening of the peak in temperature-dependent permittivity, narrowing of P–E hysteresis loops and decreasing size of ferroelectric domains resulting in polar nanodomains for x = 0.20 composition. The relaxor behavior was additionally confirmed by Vogel–Fulcher analysis. For the x ≥ 0.30 compositions, broad high-temperature anomalies are observed in dielectric permittivity versus temperature measurements in addition to the frequency-dispersive peak located close to room temperature. These samples also exhibit pinched P–E hysteresis loops. The observed pinching is most probably related to the reorganization of polar nanoregionsmore »under the electric field as shown by synchrotron X-ray diffraction measurements as well as by piezo-response force microscopy analysis, while in part affected by the presence of charged point defects and anti-ferroelectric order, as indicated from rapid cooling experiments and high-resolution transmission electron microscopy, respectively.« less
2. Correlation between oxygen evolution reaction activity and surface compositional evolution in epitaxial La _0.5 Sr _0.5 Ni _1-x Fe _x O _3-δ thin films

   https://doi.org/10.1039/D2NR05373J  

   Adiga, Prajwal ; Wang, Le ; Wong, Cindy ; Matthews, Bethany E ; Bowden, Mark E ; Spurgeon, Steven Richard ; Sterbinsky, George E. ; Blum, Monika ; Choi, Min-Ju ; Tao, Jinhui ; et al ( January 2023 , Nanoscale)

   Water electrolysis can use renewable electricity to produce green hydrogen, a portable fuel and sustainable chemical precursor. Improving electrolyzer efficiency hinges on the activity of the oxygen evolution reaction (OER) catalyst. Earth-abundant, ABO3-type perovskite oxides offer great compositional, structural, and electronic tunability, with previous studies showing compositional substitution can increase the OER activity drastically. However, the relationship between the tailored bulk composition and that of the surface, where OER occurs, remains unclear. Here, we study the effects of electrochemical cycling on the OER activity of La 0.5 Sr 0.5 Ni 1-x Fe x O 3-δ (x = 0-0.5) epitaxial films grown by oxide molecular beam epitaxy as a model Sr-containing perovskite oxide. Electrochemical testing and surface-sensitive spectroscopic analyses show Ni segregation, which is affected by electrochemical history, along with surface amorphization, coupled with changes in OER activity. Our findings highlight the importance of surface composition and electrochemical cycling conditions in understanding OER performance on mixed metal oxide catalysts, suggesting common motifs of the active surface with high surface area systems.
3. A thermodynamic potential and the temperature-composition phase diagram for single-crystalline K _{1- x} Na _x NbO ₃ (0 ≤  x  ≤ 0.5)

   https://doi.org/10.1063/1.4978360  

   Pohlmann, Hannah ; Wang, Jian-Jun ; Wang, Bo ; Chen, Long-Qing ( March 2017 , Applied Physics Letters)
4. Fe _3–x InSn _x O ₆ ( x = 0, 0.25, or 0.5): A Family of Corundum Derivatives with Sn-Induced Polarization and Above Room Temperature Antiferromagnetic Ordering

   https://doi.org/10.1021/acs.chemmater.2c00312  

   Frank, Corey E. ; McCabe, Emma E. ; Orlandi, Fabio ; Manuel, Pascal ; Tan, Xiaoyan ; Deng, Zheng ; Jin, Changqing ; Croft, Mark ; Emge, Thomas ; Yu, Shukai ; et al ( June 2022 , Chemistry of Materials)
5. Synthesis and Characterization of SrFe _x Mn _1–x (O,F) _3−δ Oxide (δ = 0 and 0.5) and Oxyfluoride Perovskite Films

   https://doi.org/10.1021/acs.inorgchem.0c01148  

   Wang, Jiayi ; Lefler, Benjamin M. ; May, Steven J. ( July 2020 , Inorganic Chemistry)

   We report the synthesis and characterization of as-grown SrFexMn1-xO2.5 epitaxial films, which were also subjected to post-growth oxidation and topotactic fluorination to obtain SrFexMn1-xO3 and SrFexMn1-xO(2.5-d)Fg films. We show how both the B-site cation and anion composition influence the structural, electronic, and optical properties of this family of perovskite materials. The Fe substitution of Mn in SrMnO2.5 gradually expands the c-axis parameter, as indicated by X-ray diffraction. With increasing x, the F content incorporated under identical fluorination conditions increases, reaching its maximum in SrFeO(2.5-d)Fg. In the compounds with mixed B-site occupation, the Fe 2p photoemission peaks are shifted upon fluorination while the Mn 2p peaks are not, suggesting inductive effects lead to asymmetric responses in how F alters the Mn and Fe bonds. Electronic transport measurements reveal all compounds are insulators, with the exception of SrFeO3, and demonstrate that fluorination increases resistivity for all values of x. Optical absorption spectra in the SrFexMn1-xO2.5 and SrFexMn1-xO3 films evolve systematically as a function of x, consistent with a physical scenario in which optical changes with Fe substitution arise from a linear combination of Mn and Fe 3d bands within the electronic structure. In contrast, the F incorporation induces non-linear changes to themore »optical response, suggesting a more complex impact on the electronic structure in materials with concurrent B-site and anion site substitution.« less