To achieve good long-term temperature stability in devices used in energy-conversion applications, this study is aimed at developing combined ceramics, referred to as PZN-PMN-PZT, comprising Pb(Zn_1/3Nb_2/3)O₃ (PZN) and Pb(Mn_1/3Nb_2/3)O₃ (PMN), which are typical relaxor ferroelectric materials, and Pb(Zr_,Ti)O₃ (PZT). The piezoelectric properties were compared based on several parameters according to the change in the composition ratio between relaxor materials, amounts of Sb₂O₃ dopant, and Zr/Ti ratio in the PZT system. Finally, we established optimal poling conditions to improve the electrical properties of the optimized piezoelectric material, based on the evaluation of ceramic properties according to the applied voltage during the poling process. The optimized composition of the investigated piezoelectric ceramics is represented by 0.14PZN-0.06PMN-0.80PbZr_0.49Ti_0.51 + 0.3 wt.% CuO + 0.3 wt.% Fe₂O₃ with 0.1 wt.% Sb₂O₃ doping, which yielded the superior properties (d₃₃ = 361 pC/N, Q_m = 1234, T_c = 306 °C).

Optimization of equipment structure and process conditions is essential to obtain thin films with the required properties, such as film thickness, trapped charge density, leakage current, and memory characteristics, that ensure reliability of the corresponding device. In this study, we fabricated metal–insulator–semiconductor (MIS) structure capacitors using HfO₂ thin films separately deposited by remote plasma (RP) atomic layer deposition (ALD) and direct-plasma (DP) ALD and determined the optimal process temperature by measuring the leakage current and breakdown strength as functions of process temperature. Additionally, we analyzed the effects of the plasma application method on the charge trapping properties of HfO₂ thin films and properties of the interface between Si and HfO₂. Subsequently, we synthesized charge-trapping memory (CTM) devices utilizing the deposited thin films as charge-trapping layers (CTLs) and evaluated their memory properties. The results indicated excellent memory window characteristics of the RP-HfO₂ MIS capacitors compared to those of the DP-HfO₂ MIS capacitors. Moreover, the memory characteristics of the RP-HfO₂ CTM devices were outstanding as compared to those of the DP-HfO₂ CTM devices. In conclusion, the methodology proposed herein can be useful for future implementations of multiple levels of charge-storage nonvolatile memories or synaptic devices that require many states.

A multilayer piezoelectric material was fabricated using piezoelectric materials with low-temperature sintering capabilities and high piezoelectric coefficients to develop a functionally superior piezoelectric speaker with a large-displacement deformation. A soft relaxor was utilized to prepare the component materials, with the optimized composition of the investigated piezoelectric ceramics represented by $0.2Pb\left({\left(Z{n}_{0.8}N{i}_{0.2}\right)}_{\frac{1}{3}}N{b}_{\frac{2}{3}}\right)O_3-0.8Pb\left(Z{r}_{0.5}T{i}_{0.5}\right)O_3$. $L{i}_{2}C{O}_3$ was added to assist the low-temperature sintering conducted at 875 °C, which yielded a multilayer piezoelectric material with superior properties ($d_{33}$= 500 pC N⁻¹, $k_p$= 0.63, $g_{33}$= 44 mV N⁻¹). A multilayer piezoelectric actuator with a single-layer thickness of ~40 µm and dimensions of 12 × 16 mm² was fabricated by tape casting the prepared green sheets. Finite element analysis revealed that the use of a PEEK film and a smaller silicone–rubber film as a composite in the diaphragm realized optimal frequency-response characteristics; the vibrations generated by the piezoelectric element were amplified. The optimal structure obtained via simulations was applied to fabricate an actual piezoelectric speaker with dimensions of 20 × 24 × 1 mm³. The actual measurements exhibited a sound pressure level of ~75 dB and a total harmonic distortion ≤15% in the audible frequency range (250–20,000 Hz) at an applied voltage of 5$V_p$.

ZnO is one of the most widely used inorganic sunscreens, owing to its fine particle size and UV light shielding capability. However, powders at nanosizes can be toxic and cause adverse effects. The development of non-nanosized particles has been slow. The present work investigated synthesis methods of non-nanosized ZnO particles for ultraviolet protection application. By altering the starting material, KOH concentration, and input speed, the ZnO particles can be obtained in different forms, including needle type, planar type, and vertical wall type. Cosmetic samples were made by mixing different ratios of synthesized powders. The physical properties and the UV blockage efficacy of different samples were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analyzer (PSA), and ultraviolet/visible (UV/Vis) spectrometer. The samples with 1:1 ratio of needle-type ZnO and vertical wall-type ZnO exhibited superior light blocking effect owing to improved dispersibility and prevention of particle agglomeration. The 1:1 mixed sample also complied with the European nanomaterials regulation due to the absence of nanosized particles. With superior UV protection in the UVA and UVB regions, the 1:1 mixed powder showed potential to be used as a main ingredient in UV protection cosmetics.

Hf_0.5Zr_0.5O₂ (HZO) thin film exhibits ferroelectric properties and is presumed to be suitable for use in next-generation memory devices because of its compatibility with the complementary metal–oxide–semiconductor (CMOS) process. This study examined the physical and electrical properties of HZO thin films deposited by two plasma-enhanced atomic layer deposition (PEALD) methods— direct plasma atomic layer deposition (DPALD) and remote plasma atomic layer deposition (RPALD)—and the effects of plasma application on the properties of HZO thin films. The initial conditions for HZO thin film deposition, depending on the RPALD deposition temperature, were established based on previous research on HZO thin films deposited by the DPALD method. The results show that as the measurement temperature increases, the electric properties of DPALD HZO quickly deteriorate; however, the RPALD HZO thin film exhibited excellent fatigue endurance at a measurement temperature of 60 °C or less. HZO thin films deposited by the DPALD and RPALD methods exhibited relatively good remanent polarization and fatigue endurance, respectively. These results confirm the applicability of the HZO thin films deposited by the RPALD method as ferroelectric memory devices.

Plasma-enhanced atomic layer deposition (ALD) is a common method for fabricating Hf_0.5Zr_0.5O₂ (HZO) ferroelectric thin films that can be performed using direct-plasma (DP) and remote-plasma (RP) methods. This study proposed co-plasma ALD (CPALD), where DPALD and RPALD are applied simultaneously. HZO films fabricated using this method showed wake-up-free polarization properties, no anti-ferroelectricity, and high fatigue endurance when DPALD and RPALD started simultaneously. To minimize defects in the film that could negatively affect the low polarization properties and fatigue endurance, the direct plasma power was reduced to 75 W. Thus, excellent fatigue endurance for at least 10⁹ cycles was obtained under a high total remanent polarization of 47.3 μC/cm² and an applied voltage of 2.5 V. X-ray photoelectron spectroscopy and transmission electron microscopy were used to investigate the mechanisms responsible for these properties. The HZO films fabricated by CPALD contained few lattice defects (such as nonstoichiometric hafnium, nonlattice oxygen, and residual carbon) and no paraelectric phase (m-phase). This was attributed to the low-carbon residuals in the film, as high-energy activated radicals were supplied by the adsorbed precursors during film formation. This facilitated a smooth transition to the o-phase during heat treatment, which possessed ferroelectric properties.