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1. Aliovalent substitution of Pb with (Li _1/2 Bi _1/2 ) in PbZrO ₃ model system

   https://doi.org/10.1111/jace.20520  

   Taylor, Odin D; Hoyt, Andrew; Tan, Xiaoli (August 2025, Journal of the American Ceramic Society)

   Abstract Li⁺and Bi³⁺(at 1:1 ratio) substitution of Pb²⁺in the model compound PbZrO₃is investigated. It is found that [Pb_1−x(Li_1/2Bi_1/2)_x]ZrO₃ceramics remain phase pure of orthorhombic perovskite atx = 0.05, are almost phase pure atx = 0.10 and 0.15, and contain minor amounts of impurity phases atx = 0.20. The substitution allows the ceramics to be sintered to a high density at reduced temperatures, and at the same time, significantly enhances the dielectric breakdown strength. At 160°C when reversible antiferroelectric (AFE)–ferroelectric (FE) phase transitions are observed in all compositions, the chemical substitution is shown to reduce the electric hysteresis, increase the energy storage density, and improve the energy efficiency. The results will help design future high‐performance ceramics for energy storage capacitors. It is further observed that the (Li_1/2Bi_1/2) substitution of Pb in PbZrO₃weakly impacts the dielectric behavior of the ceramics: The temperature at dielectric maximum,T_m, varies within a narrow range of 232.4–237.6°C; the relaxation parameter in the paraelectric phase,γ, stays close to unity and barely changes; and the diffuseness parameter of the phase transition atT_m,d, remains low. Defect dipoles of preferably along 〈1 1 0〉 directions are proposed to explain the un‐disrupted long‐range AFE order in the [Pb_1−x(Li_1/2Bi_1/2)_x]ZrO₃ceramics. 

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2. Effect of Precursor Purge Time on Plasma-Enhanced Atomic Layer Deposition-Prepared Ferroelectric Hf _0.5 Zr _0.5 O ₂ Phase and Performance

   https://doi.org/10.1021/acsomega.5c01112  

   Choi, Yong Kyu; Holsgrove, Kristina; Watson, Andrea; Aronson, Benjamin L; Lenox, Megan K; Shvilberg, Liron; Zhou, Chuanzhen; Fields, Shelby S; Wang, Shihao; McDonnell, Stephen J; et al (May 2025, ACS Omega)

   Hafnium oxide-based thin films, in particular hafnium zirconium oxide (HZO), have potential for applications in nonvolatile memory and energy harvesting. Atomic layer deposition (ALD) is the most widely used method for HZO deposition due to its precise thickness control and ability to provide conformal coverage. Previous studies have shown the effects of different metal precursors, oxidizer precursors, and process temperatures on the ferroelectric properties of HZO. However, no mechanism has been identified to describe the different phase stabilities as the metal precursor purge time varies. This study investigates how varying the metal precursor purge time during plasma-enhanced ALD (PE-ALD) influences the phases and properties of the HZO thin films. Grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy, and scanning transmission electron microscopy are used to study the changes in phase of HZO with variation of the metal precursor purge time during the PE-ALD process. The phases observed are correlated with polarization and relative permittivity responses under an electric field, including wake-up and endurance effects. The resulting phases and properties are linked to changes in composition, as measured using time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. It is shown that short metal precursor purge times result in increased carbon and nitrogen impurities and stabilization of the antipolar Pbca phase. Long purge times lead to films comprising predominantly the ferroelectric Pca21 phase. 

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3. Medium‐Entropy Engineering of Magnetism in Layered Antiferromagnet Cu _x Ni _{2(1‐ x )} Cr _x P ₂ S ₆

   https://doi.org/10.1002/adfm.202418722  

   Upreti, Dinesh; Basnet, Rabindra; Sharma, M M; Chhetri, Santosh Karki; Acharya, Gokul; Nabi, Md_Rafique Un; Sakon, Josh; Benamara, Mourad; Mortazavi, Mansour; Hu, Jin (December 2024, Advanced Functional Materials)

   Abstract Antiferromagnetic van der Waals‐typeM₂P₂X₆compounds provide a versatile material platform for studying 2D magnetism and relevant phenomena. Establishing ferromagnetism in 2D materials is technologically valuable. Though magnetism is generally tunable via a chemical way, it is challenging to induce ferromagnetism with isovalent chalcogen and bimetallic substitutions inM₂P₂X₆. Here, we report co‐substitution of Cu¹⁺and Cr³⁺for Ni²⁺in Ni₂P₂S₆, creating Cu_xNi_2(1‐x)Cr_xP₂S₆medium‐entropy alloys spanning a full substitution range (x= 0 to 1). Such substitution strategy leads to a unique evolution in crystal structure and magnetic phases that are distinct from traditional isovalent bimetallic doping, with Cu and Cr co‐substitution enhancing ferromagnetic correlations and generating a weak ferromagnetic phase in intermediate compositions. This aliovalent substitution strategy offers a universal approach for tuning layered magnetism in antiferromagnetic systems, which along with the potential for light‐matter interaction and high‐temperature ferroelectricity, can enable multifunctional device applications. 

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4. Machine learning–guided optimization of coercive field in Al _{1− x} Sc _x N thin films for nonvolatile memory

   https://doi.org/10.1111/jace.20347  

   Das, Shaon; Garg, Prachi; Mazumder, Baishakhi (April 2025, Journal of the American Ceramic Society)

   Abstract This study employs a data‐driven machine learning approach to investigate specific ferroelectric properties of Al_1−xSc_xN thin films, targeting their application in next‐generation nonvolatile memory (NVM) devices. This approach analyzes a vast design space, encompassing over a million data points, to predict a wide range of coercive field values that are crucial for optimizing Al_1−xSc_xN‐based NVM devices. We evaluated seven machine learning models to predict the coercive field across a range of conditions, identifying the random forest algorithm as the most accurate, with a testR²value of 0.88. The model utilized five key features: film thickness, measurement frequency, operating temperature, scandium concentration, and growth temperature to predict the design space. Our analysis spans 13 distinct scandium concentrations and 13 growth temperatures, encompassing thicknesses from 9–1000 nm, frequencies from 1 to 100 kHz, and operating temperatures from 273 to 700 K. The predictions revealed dominant coercive field values between 3.0 and 4.5 MV/cm, offering valuable insights for the precise engineering of Al_1−xSc_xN‐based NVM devices. This work underscores the potential of machine learning in guiding the development of advanced ferroelectric materials with tailored properties for enhanced device performance. 

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5. Large Enhancements in Optical and Piezoelectric Properties in Ferroelectric Zn _{1‐ x} Mg _x O Thin Films through Engineering Electronic and Ionic Anharmonicities

   https://doi.org/10.1002/apxr.202300003  

   Zu, Rui; Ryu, Gyunghyun; Kelley, Kyle P.; Baksa, Steven M.; Jacques, Leonard C.; Wang, Bo; Ferri, Kevin; He, Jingyang; Chen, Long‐Qing; Dabo, Ismaila; et al (May 2023, Advanced Physics Research)

   Abstract Multifunctionality as a paradigm requires materials exhibiting multiple superior properties. Integrating second‐order optical nonlinearity and large bandgap with piezoelectricity can, for example, enable broadband, strain‐tunable photonics. Though very different phenomena at distinct frequencies, both second‐order optical nonlinearity and piezoelectricity are third‐rank polar tensors present only in acentric crystal structures. However, simultaneously enhancing both phenomena is highly challenging since it involves competing effects with tradeoffs. Recently, a large switchable ferroelectric polarization of ≈80 μC cm⁻²was reported in Zn_1‐xMg_xO films. Here, ferroelectric Zn_1‐xMg_xO is demonstrated to be a platform that hosts simultaneously a 30% increase in the electronic bandgap, a 50% enhancement in the second harmonic generation (SHG) coefficients, and a near 200% improvement in the piezoelectric coefficients over pure ZnO. These enhancements are shown to be due to a 400% increase in the electronic anharmonicity and a ≈200% decrease in the ionic anharmonicity with Mg substitution. Precisely controllable periodic ferroelectric domain gratings are demonstrated down to 800 nm domain width, enabling ultraviolet quasi‐phase‐matched optical harmonic generation as well as domain‐engineered piezoelectric devices. 

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