Promising Candidate Materials For Applications Research Articles

A deep neural network potential model for transition metal diborides

Transition metal diborides (TMB2s) are renowned for their high melting point and exceptional wear, corrosion, and erosion resistance, making them promising candidate materials for applications in extreme environments. As such, there is an urgent need for reliable material design tools for TMB2s to improve efficiency in developing new materials. To address this need, we have developed a domain-specific medium-scale interatomic potential model for TMB2s that encompasses elements Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and B. The prediction errors in energy and force of our model are 8.8 meV/atom and 387 meV/Å, respectively. Furthermore, the model demonstrates high accuracy in predicting various material properties, including lattice parameters, elastic constants, equations of states, and melting points, as well as grain boundary segregations. By providing a reliable and efficient tool for material design, this model will play a crucial role in the development of new, high-performance TMB2s for use in extreme environments.

Tunable Band Alignment and Optoelectronic Structure of Cu2Se/PtX2 (X=Se,Te) Heterostructures: under Strain and Electric Field

Two-dimensional (2D) material-based van der Waals heterostructures (vdWHs) are an emerging strategy for regulating the electronic properties of two-dimensional materials. This study investigated the effects of a vertical electric field and strain on the band alignment transition and optoelectronic properties of Cu2Se/PtSe2 (PtTe2) vdWHs using density functional theory calculations. Cu2Se/PtSe2 vdWHs exhibited type-I to type-II band alignment transformation under an in-plane strain, interlayer distance, and electric field of 2%, 2.40 Å, and -0.40 V/Å, respectively. Moreover, Cu2Se/PtTe2 vdWH demonstrated a rich transition of types I, II, and III band alignments with in-plane strain. The absorption spectra of Cu2Se/PtSe2 (PtTe2) vdWHs show a certain degree of blue and red shift phenomenon upon the application of strain and electric fields. The predicted power conversion efficiencies at 3% in-plane strain with an interlayer distance of 3.40 Å for Cu2Se/PtSe2 (PtTe2) vdWHs were observed to be as high as 22.58% (19.80%). Thus, our work demonstrated that both strain and electric field can effectively and flexibly control the electronic properties of Cu2Se/PtSe2 (PtTe2) vdWHs, making them a promising candidate material for applications in photodetectors and field-effect transistors.

Pyrochlore-type lanthanide titanates and zirconates: Synthesis, structural peculiarities, and properties

This contribution provides a thorough examination of the structural characteristics of pyrochlore-type lanthanide titanates and zirconates Ln2Ti2O7 and Ln2Zr2O7, across various length scales. This paper also examines their processing, interesting physical properties (electrical, magnetic, and thermal characteristics), and responses to high pressure and ion irradiation. Brief sections on the elemental oxides' crystal chemistry, pertinent phase diagrams, and energetics of defect formation are also provided. Pyrochlore-type Ln2Ti2O7 and Ln2Zr2O7 stand out as truly multifunctional materials. Moreover, they have emerged as fascinating materials due to magnetic geometrical frustration, arising from the ordering of magnetic Ln3+ and non-magnetic Ti4+ (or Zr4+) cations into separate, interpenetrating lattices of corner-sharing tetrahedra. This results in a diverse array of exotic magnetic ground states, such as spin-ice (e.g., Dy2Ti2O7 or Ho2Ti2O7) or quantum spin ice (e.g., Tb2Ti2O7), observed at both low and room temperatures. They also exhibit varied electrical and electrochemical characteristics. Some members such as Gd2Zr2O7, function as fast ion conductors with a conductivity (σ) of ≈10−2 S·cm−1 at 800 °C and activation energy (Ea) ranging from 0.85 to 1.52 eV, depending on the degree of structural disorder. Others, such as Gd2TiMoO7, are mixed ionic-electronic conductors with σ ≈ 25 S·cm−1 at 1000 °C, making them promising candidate materials for applications in energy conversion and storage devices and oxygen separation membranes. Their exceptionally low thermal conductivity (e.g., κ ∼ 1.1–1.7 W·m−1·K−1 between 700 and 1200 °C for Ln2Zr2O7), close to the glass-like lower limit of highly disordered solids, positions them as valuable materials for thermal barrier coatings. They can also effectively accommodate actinides (e.g., Pu, Np, Cm, Am) in solid solutions and sustain prolonged exposure to radiation due to alpha-decay events, while preserving the integrity of the periodic atomic structure. Proposed as major components in actinide-bearing ceramics, they contribute to the long-term immobilization and disposal of long-lived waste radionuclides from nuclear programs. Some of these properties are displayed simultaneously, opening avenues for new applications. Despite the wealth of data available in the literature, this review highlights the need for a better understanding of order/disorder processes in pyrochlore-type materials and the influence of the structural length scale on their physical and chemical properties. Recent experimental evidence has revealed that pyrochlore short-range structure is far more complex than originally thought. Moreover, pyrochlore local structure is now believed to include short-range, lower symmetry, ordered domains, such as the orthorhombic weberite-type of structure. Notably, short- and long-range structures appear decoupled across different length scales and temperature regimes, and these differences persist even in well-ordered samples. We believe that the pyrochlore structure offers a unique opportunity for examining the interplay between chemical composition, defect chemistry, and properties. In Memoriam: Rodney C. Ewing, Fondly Remembered.

Hygro‐Dynamic and Conductive Actuator That Restructures and Heals by Water

AbstractThe prospects of endowing stimuli‐responsive materials with various life‐like behaviors are promoting the development of intelligent robotic and electronic devices. However, it is challenging to incorporate stimuli‐responsive actuating and healing capabilities into one single material system. Herein, the design and assembly of humidity‐responsive thin films composed of poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and sodium carboxymethyl cellulose (NaCMC) forming a conducting polymer composite through a physically cross‐linked and hydrogen‐bonded supramolecular network are described. Owing to its enhanced dynamics of hydrogen bonding at an elevated humidity, the PEDOT:PSS/NaCMC thin film exhibits a rapid humidity‐responsive actuating performance in an environment with humidity gradient, as well as a repairing function of the structural, mechanical, electrical, and actuating properties after being damaged through a humidifying‐drying cycle. Based on a combined analytical approach, a structural model is proposed for the rearrangement of the thin film when being exposed to stepwise humidity levels at multi‐length scales. Due to the structural rearrangement powered by humidity variations, the film exhibits tunable actuating and healing performance, which makes it a promising candidate material for applications in intelligent soft robotics such as artificial muscles.

Luminescent properties of Y2LaCaGa3ZrO12: Bi3+, Al3+ cyan phosphors for application in white light emitting diodes

High-quality white light can be obtained from a mixture of blue, green, and red phosphors excited by ultraviolet chips. However, this approach suffers from the presence of a cyan gap in the emission spectra, which hinders further improvement in the color rendering index (CRI). The obvious solution to this problem should be the development of efficient ultraviolet-excited cyan phosphors to fill this gap. Therefore, a series of Y2LaCaGa3ZrO12: xBi3+ (x = 0–0.1) cyan phosphors were synthesized via high-temperature solid-state reaction method, and their properties were systematically characterized. The Bi3+ ion in Y2LaCaGa3ZrO12 exhibits dual-mode luminescence with emission bands peaking at 356 nm and 483 nm, originating from the 3P1→1S0 transitions of Bi3+ at different sites. The ultraviolet emission is attributed to Bi3+ occupying 8 coordination sites, while the cyan emission arises from Bi3+ in 6 coordination sites. It is noteworthy that the emission intensity and thermal stability of the phosphors can be further improved by partially substituting Ga3+ with Al3+. By incorporating Y2LaCaGa3ZrO12: 0.02Bi3+ or Y2LaCaGa2.7Al0.3ZrO12: 0.02Bi3+ with commercial phosphors and depositing them onto a 365 nm ultraviolet chip, the prototype white light emitting diodes (w-LEDs) exhibits white light with high CRI of 89.6 and 90.4, respectively. These results validate the potential of Bi3+ activated Y2LaCaGa3-yAlyZrO12 (y = 0–1) cyan phosphor as a promising candidate material for application in UV-excited w-LEDs.

Precipitates change of P92 steel under 3.5 MeV Fe13+ ion irradiation at 400 °C

9–12% Cr ferritic/martensitic steels are promising candidate materials for applications in fourth generation nuclear reactors. 9%Cr ferritic/martensitic steel P92 was normalized at 1050 °C for 0.5 h and subsequently tempered at 765 °C for 1 h. The precipitates of the normalized-and-tempered steel after 3.5 MeV Fe13+ ion irradiation at 400 °C to 0.66 dpa were studied using transmission electron microscopes. After irradiation, the number of precipitates increased, especially for the number of large-sized precipitates, and there was an increase in the overall size of precipitates. Pre-existing Cr-rich M23C6, Nb-rich MX and V-rich MX precipitates in the normalized-and-tempered steel still existed in the irradiated steel, and the M23C6 precipitates remained almost unchanged in their composition. Irradiation-induced Nb-rich M6C5 carbide with a base-centered monoclinic structure, V-rich M2X (V2C type) carbonitride with a simple orthorhombic crystal structure, and Fe71Cr26(Mo,W)3 (σ-FeCr type) intermetallic compound with a simple teragonal crystal structure were identified in the irradiated steel. The formation of these irradiation-induced phases is also discussed.

Stable silicone oil based ferrofluids with well low-temperature fluidity applied to magnetic fluid seal

Stable silicone oil based ferrofluids with high magnetization and low-temperature fluidity have been successfully synthesized. The ferrofluids containing surfactant coated magnetite nano particles with average diameters of 10 nm could maintain stable for more than 2 months. Silicone oil based ferrofluids could reach a saturated magnetization of 24.6 emu/g, which ensures them to be easily controlled by the magnetic fields. Silicone oil based ferrofluids could maintain their fluidity at −40 °C while the LAN15 (engine oil) based ferrofluids could not. The property of low- temperature fluidity is systematically explained by the magneto-rheological experiments. This outstanding property of low-temperature fluidity ensures the silicone oil based ferrofluids a promising candidate material for applications in magnetic fluid seal. Herein, the magnetic rotary sealing performed by different ferrofluids at low temperature are systematically characterized. As result, the silicone oil based ferrofluids have lower starting torque and higher sealing pressure endurance compared to LAN15 based ferrofluids at −40 °C. Based on our experimental results, the theoretical analysis and numerical simulation results systematically explained the advantages silicone oil based ferrofluids have on low-temperature magnetic fluid seal.

Cellulose-g-tetraethylenepentamine dual-function imprinted polymers selectively and effectively adsorb and remove 4-nitrophenol and Cr(VI)

A cellulosic material has been synthesized that could efficiently and selectively adsorb organic and inorganic contaminants from aqueous solutions without interference from competing adsorption sites. Cellulose-graft-tetraethylenepentamine molecular imprinted polymer (C-TEPA-MIP) was synthesized by using 4-nitrophenol (4-NP) as the template. The C-TEPA-MIP adsorbent could adsorb 4-NP and Cr(VI) simultaneously and selectively, without being affected by the competitive adsorption sites of each of these pollutants. The adsorption of 4-NP was predominantly due to the imprinted sites of 4-NP in C-TEPA-MIP that were located inside of the adsorbent, whereas that of Cr(VI) was primarily due to the amine groups of TEPA found on the surface of the adsorbent. Compared with the non-imprint polymer synthesized without the template, C-TEPA-MIP showed higher selectivity for both 4-NP and Cr(VI) in unitary and binary systems. In addition, C-TEPA-MIP exhibited good stability and recyclability for 4-NP, which makes it a promising candidate material for applications concerning wastewater treatment.Graphical abstract

Synthesis, physicochemical and optical characterizations of a new isatin hydrazone derivative and its ZnO-complex for potential energy conversion and storage applications

We synthesized a novel isatin hydrazone derivative 3-(((E)-3-ethoxy-2-hydroxybenzylidene)hydrazineylidene)indolin-2-one (IL) via condensation of isatin hydrazide with 3-ethoxy-salicylaldehyde in methanol. Then ZnO was chelated with the ligand (IL) to produce a novel ZnOIL complex. The characteristics of the IL and ZnOIL compounds were compared using various techniques, including nuclear magnetic resonance, ultraviolet–visible, infrared, and mass spectroscopy, and elemental analyses to confirm their chemical compositions. The optical properties of the IL and ZnOIL thin films were studied based on spectroscopic measurements of their absorbance, transmittance, and reflectance within the range of 300–2500 nm. The optical constants, dielectric parameters, and dispersion energies were determined and interpreted. The electronic inter-band transitions of the IL and ZnOIL films were characterized by indirect allowed transitions. The value of the optical band gap (Eg) was determined as 2.14 eV for the IL film, but chelation of IL with ZnO decreased Eg to 2.02 eV. The surface and volume energy loss functions were lower for ZnOIL compared with IL. The structural and the optical features of ZnOIL may be tuned, and thus it is a promising candidate material for applications in energy conversion and storage devices.

Coarse-grained molecular dynamics simulation of deformation and fracture in polycarbonate: Effect of molar mass and entanglement

Polycarbonate is a promising candidate material for applications as structural element owing to its prominent properties including lightness, strength and toughness. To sustain complex mechanical loadings and resist fracture, it is essential to obtain reliable constitutive relations of deformation. Such constitutive laws that are used for the design and optimization of polymer-based engineering products can be directly obtained from computer simulations. In this study we performed coarse-grained molecular dynamics (CGMD) simulations of polycarbonate to gain a better understanding of the deformation and fracture mechanisms at the molecular level and to clarify its dependency on the molecular structure. In particular, we investigated how the state of entanglement influences the deformation behavior for simulation models with various molar masses. We found a significant effect of the molar mass on the stress-strain curves; i.e. the larger the molar mass is, the larger stress can be reached after yielding, suggesting that molar mass plays a major role in the brittle-ductile transition of polycarbonate.

Computational Study of Short-Pulse Laser-Induced Generation of Crystal Defects in Ni-Based Single-Phase Binary Solid–Solution Alloys

Single-phase concentrated solid–solution alloys exhibit enhanced mechanical characteristics and radiation damage resistance, making them promising candidate materials for applications involving an ...

Assembly of Zeolite-like Metal-Organic Framework: An Indium-ZMOF Possessing GIS Topology and High CO2 Capture.

An In-ZMOF material, [(CH3)2NH2][In(ABTC)]·3DMF (JLU-MOF52), has been synthesized by using 2,2',5,5'-azobenzenetetracarboxylic acid (H4ABTC) as a linker, which coordinated to four [In(O2C)4]- secondary building units (SBUs) to generate a 3D framework. JLU-MOF52 is constructed by a rare 4 + 4 strategy from 4-connected tetrahedral [In(O2C)4]- SBUs and tetrahedral ligands, which can be described as a (4, 4)-connected and forbidden interpenetrated zeolite-like MOF with GIS topology. The framework exhibits significant advantages in terms of chemical stability. N2 adsorption study of the activated JLU-MOF52 material reveals a Langmuir and a BET surface area is 1302 and 966 m2 g-1, respectively. Furthermore, the adsorption amount of CO2 for JLU-MOF52 is studied under 1 atm, which exhibits the highest CO2 capture ability at 273 K among the ZMOFs materials with GIS topology. These characteristics make JLU-MOF52 promising candidate materials for application in moderating increasing atmospheric CO2 levels.

Tunable direct-indirect band gaps of ZrSe2 nanoribbons

The atomic and electronic structures of armchair and zigzag ZrSe2 nanoribbons have been investigated systematically. Both the armchair and zigzag ZrSe2 nanoribbons are nonmagnetic semiconductors, while their bandgaps show quite different behaviors depending on the ribbon width. We find that all the zigzag ribbons possess direct energy gaps, which smoothly decline with the increasing ribbon width. On the other hand, energy gaps for the armchair ribbons change from direct gaps to indirect ones as the ribbon width increases and exhibit a width-dependent oscillation behavior. Moreover, the semiconducting behaviors and the bandgap types are robust, and they remain unchanged in bilayer and multilayer thin films with inter-layer interactions. These findings indicate that ZrSe2 nanoribbons are promising candidate materials for applications in nanoelectronic devices.

Innovatively Continuous Mass Production Couette-taylor Flow: Pure Inorganic Green-Emitting Cs4PbBr6 Perovskite Microcrystal for display technology

We report for the first time the mass production of Cs4PbBr6 perovskite microcrystal with a Couette-Taylor flow reactor in order to enhance the efficiency of the synthesis reaction. We obtained a pure Cs4PbBr6 perovskite solid within 3 hrs that then realized a high photoluminescence quantum yield (PLQY) of 46%. Furthermore, the Cs4PbBr6 perovskite microcrystal is applied with red emitting K2SiF6 phosphor on a blue-emitting InGaN chip, achieving a high-performance luminescence characteristics of 9.79 lm/W, external quantum efficiency (EQE) of 2.9%, and correlated color temperature (CCT) of 2976 K; therefore, this perovskite is expected to be a promising candidate material for applications in optoelectronic devices.

MOF-derived hollow NiO–ZnO composite micropolyhedra and their application in catalytic thermal decomposition of ammonium perchlorate

Ni(II)-doped Zn-based coordination polymer particles (Ni(II)-doped Zn-CPPs) with controllable shape and size were successfully synthesized by solvothermal method, which further transformed to porous ZnO–NiO composite micropolyhedra without significant alterations in shape by calcination in air. Those products were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), infrared spectroscopy (IR) and gas adsorption measurements. The catalytic activity of ZnO–NiO composites for the thermal decomposition of ammonium perchlorate (AP) was investigated. The result shows that all ZnO–NiO composites efficiently catalyzed the thermal decomposition of AP, and NiO–ZnO composite hollow octahedrons have the highest catalytic efficiency compared with that of most materials reported to now, indicating that porous ZnO–NiO composite micropolyhedra could be a promising candidate material for application in AP-based propellant.

Ultrafast Zero-Bias Photocurrent in GeS Nanosheets: Promise for Photovoltaics

Ferroelectric semiconductors have been predicted to exhibit strong zero-bias shift current, spurring the search for ferroelectric semiconductors with band gaps in the visible range as candidates for so-called shift current photovoltaics with efficiencies not constrained by the Schockley–Queisser limit. Recent theoretical works have predicted that two-dimensional IV–VI monochalcogenides are multiferroic and capable of generating significant shift currents. Here we present experimental validation of this prediction, observing ultrafast shift currents by detecting terahertz electromagnetic pulses emitted by the photoexcited GeS nanosheets without external bias. We explore excitation fluence, orientation, and excitation polarization dependence of the terahertz emission to confirm that shift currents are indeed responsible for the observed emission. Experimental observation of zero-bias photocurrents puts GeS nanosheets forth as a promising candidate material for applications in third-generation photovoltaics ...

A low-loss dielectric using CaTiO<sub>3</sub>-modified Mg<sub>1.8</sub>Ti<sub>1.1</sub>O<sub>4</sub> ceramics for applications in dielectric resonator antenna

The microwave dielectric properties of (1-x)Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.1</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -xCaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramics prepared by the mixed oxide route have been investigated. Spinel-structured Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.1</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , ilmenite-structured MgTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and perovskite-structured CaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> were coexisted and the three-phases system was confined by X-ray diffraction patterns, EDX analysis and it also leads to near-zero τf. The microstructures of the ceramics were characterized by SEM. The microwave dielectric properties of the ceramics can be effectively controlled by varying the x value. For practical applications, a fine combination of microwave dielectric properties (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ~ 19.61, Q×f~ 72,700 GHz at 9.03 GHz, τ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> ~ -3.7 ppm/°C) was achieved for 0.91Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.8</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.1</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> -0.09CaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramics sintered at 1330°C for 4 h, which makes it is a very promising candidate material for applications in dielectric resonator antenna. A new triple-band dielectric resonator antenna fed by a coplanar waveguide is presented. The proposed antenna, composed of a high permittivity dielectric resonator and printed on FR4 substrate, is fed by a 50 Ω coplanar waveguide transmission line. In order to achieve wideband applications, the antenna with two parasitic inverted-L strip is demonstrated to generate two resonant frequencies covering 3.5 and 5.2 GHz. The measured results show that the antenna covers the frequency bands 2.30-2.72, 3.45-3.61, and 5.05-6.23 GHz with less than -10 dB of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> . The frequency response of the simulation results shows good agreement with the measured data. Good antenna gain, radiation efficiency and radiation patterns of the proposed antenna have also been observed across the operation band. Details of the proposed antenna design and experimental results are presented and discussed.

Analysis of the Fragmentation of AlON and Spinel Under Ballistic Impact

It has been demonstrated that significant weight reductions can be achieved, compared to conventional glass-based armor, when a transparent ceramic is used as the strike face on a glass-polymer laminate. Magnesium aluminate spinel (MgAl2O4) and AlON are promising candidate materials for application as a hard front layer in transparent armor. Comprehensive, systematic investigations of the fragmentation of ceramics have shown that the mode of fragmentation is one of the key parameters influencing the ballistic resistance of ceramics. In the study described here, the fragmentation of AlON and three types of spinel was analyzed: two types of fine grained spinel with nominal average grain sizes 0.6 μm and 1.6 μm and a bimodal grain-sized spinel with large grains of 250 μm size in a fine grain (5–20 μm) matrix were examined. The ceramic specimens of 6-mm thickness were glued to an aluminum backing and impacted with armor piercing (AP) projectiles of caliber 7.62 mm at two different velocities—850 m/s and 1100 m/s. The targets were integrated into a target box, which allowed for an almost complete recovery and analysis of the ceramic fragments. Different types of high-speed cameras were applied in order to visualize the different phases of fragment formation and ejection. A laser light-sheet illumination technique was applied in combination with high-speed cameras in order to determine size and speed of ejected ceramic fragments during projectile penetration. The application of the visualization techniques allowed for the analysis of the dynamics of the fragment formation and interaction with the projectile. A significant difference in the fragment size distributions of bimodal grain-sized spinel and AlON was observed.

The Piezoelectric Properties of (Na0.5K0.5)NbO3-K5.4Cu1.3Ta10O29Ceramics with Various K5.4Cu1.3Ta10O29Doping and Sintering Temperatures

(1-X)<TEX>$(Na_{0.5}K_{0.5})NbO_3-XK_{5.4}Cu_{1.3}Ta_{10}O_{29}$</TEX> (NKN-KCT) lead-free piezoelectric ceramics have been synthesized by the conventional solid state sintering method, and their sinterability and piezoelectric properties were investigated. Typically, this material is sintered between 1,025 and <TEX>$1,100^{\circ}C$</TEX> for 2 hours to achieve the required densification. Crystalline structures and Microstructures were analyzed by X-ray diffraction and scanning electron microscope. The density, dielectric constant (<TEX>${\varepsilon}_r$</TEX>), piezoelectric constant <TEX>$d_{33}$</TEX>, electromechanical coupling factor <TEX>$k_p$</TEX> and mechanical quality factor <TEX>$Q_m$</TEX> value of the NKN ceramics depended upon the KCT content and the sintering temperature. In particular, the KCT addition to NKN greatly improved the mechanical quality factor <TEX>$Q_m$</TEX> value. The ceramic with X = 1.0 mol% sintered at <TEX>$1,050^{\circ}C$</TEX> exhibited optimum properties (<TEX>${\varepsilon}_r$</TEX>=246, <TEX>$d_{33}$</TEX>=95, <TEX>$k_p$</TEX>=0.38 and <TEX>$Q_m$</TEX>=1,826). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

ZrO2첨가된 0.96(K0.5Na0.5)NbO3-0.04SrZrO3압전세라믹스의 환원분위기 소결

The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of <TEX>$0.96(K_{0.5}Na_{0.5})NbO_3-0.04SrZrO_3+x$</TEX> mol% <TEX>$ZrO_2$</TEX> [KNN-SZ+<TEX>$xZrO_2$</TEX>; x= 0~0.10] doped with 0.1 wt% <TEX>$MnO_2$</TEX> by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%<TEX>$H_2-97%N_2$</TEX> atmosphere at <TEX>$1,140^{\circ}C$</TEX> exhibit pure perovskite structure irrespective of the content of <TEX>$ZrO_2$</TEX>. Meanwhile, the sintering denisty and piezoelectric properties such as <TEX>$K_p$</TEX>, <TEX>$Q_m$</TEX> and <TEX>$d_{33}$</TEX> of KNN-SZ samples as a function of <TEX>$ZrO_2$</TEX> content show the maxima (<TEX>$k_p$</TEX>=28.07%, <TEX>$Q_m$</TEX>= 101.34, <TEX>$d_{33}$</TEX>= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+<TEX>$xZrO_2$</TEX> composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.