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Micromechanical simulation of ferroelectric domain processes at crack tips
摘要： The electromechanical loading situation at cracks in ferroelectric ceramics is essentially affected by domain switching. Under high electrical and/or mechanical external fields, the state of polarization and remanent strains is substantially changed at the crack tip. These irreversible dissipative processes influence the fracture toughness of the cracked ferroelectric material. In the present paper, the micromechanical domain switching processes at the crack tip are studied by numerical simulation and compared with the in situ experimental results obtained by Jones et al. (Acta Mater 55(16):5538–5548, 2007) using X-ray diffraction analyses in synchrotron. Main attention is payed to the spatial distribution of preferred domain orientation in a mechanically loaded compact tension specimen made of a soft tetragonal lead zirconate titanate ceramics. It is found that the mechanically induced favored domain orientation distribution depends on position within the plane of the CT specimen and correlates with projected deviatoric stresses and strains. Some issues concerning shortcomings in the experimental and simulation results are raised and discussed. The outcome of this type of simulations forms the basis for more realistic fracture mechanical evaluations in future.
关键词： Domain switching,Crack tip,Ferroelectric/piezoelectric materials,Fracture,Process zone
更新于2025-09-23 15:23:52
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The current-voltage characteristics of the ferroelectric p-YMnO3 thin film/bulk p-Si heterojunction over a broad measurement temperature range
摘要： The reverse and forward bias I-V characteristics of the Al/p-YMO/p-Si/Al heterojunction were measured at room temperature (RT) and over temperature range, from 50 to 320 K, and the I-V curves showed Schottky diode-like characteristics. The ideality factor and barrier height values were calculated as 0.81 and 2.62 from the forward bias I-V curve at room temperature (300 K), respectively. The YMO powder was prepared via solid state reaction technique. YMO thin films were grown on front surface of p-Si substrate by radio frequency (rf) magnetron sputtering using a polycrystalline YMO single target. The YMO thin film thickness on Si substrate was measured as ~70 nm via Dektak XT surface profilometer. The XRD, SEM, UV-Vis and XPS measurements of the YMO thin film were also performed. The bandgap energy of YMnO3 thin films was determined as 2.10 eV by UV-vis. The temperature-dependent reverse and forward bias I-V curves were evaluated in terms of thermionic emission (TE), Schottky emission, Fowler-Nordheim (F-N) tunneling and space charge-limited current (SCLC) current theories. Furthermore, it has been seen that the forward bias conduction in the junction at each temperature obeys F-N tunneling because of the linearity in the ln (I/V2) versus V-1 curves.
关键词： Polycrystalline,Heterojunction,Ferroelectric,Al/p-YMO/p-Si/Al,Schottky barrier,YMnO3,Temperature dependent current characteristics
更新于2025-09-23 15:23:52
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Enhancing pyroelectric properties in (Pb1-1.5La )(Zr0.86Ti0.14)O3 ceramics through composition modulated phase transition
摘要： Currently, there is an urgent need of extraordinary comprehensive pyroelectric materials for the wide application in detectors and energy harvesters. In this study, the (Pb1-1.5xLax)(Zr0.86Ti0.14)O3 (abbreviated as PLZT, x = 0.02, 0.03, 0.04 and 0.05) ceramics located in ferroelectric-antiferroelectric (FE-AFE) phase boundary were designed and synthesized by using conventional solid-state reaction method. The microstructures, phase structures, dielectric, ferroelectric, thermal depolarization and pyroelectric properties of the PLZT ceramics with different La content were investigated thoroughly. The XRD results show that the PLZT ceramics change from FE phase to AFE phase with increasing La content. The significant improvement of pyroelectric coefficient and figures of merit (FOMs) are achieved in the PLZT ceramics with the increase in La content because of the increased metastable ferroelectric phase under the application of electric field. The (Pb0.955La0.03)(Zr0.86Ti0.14)O3 (x = 0.03) ceramic exhibits not only high of and high depolarization temperature (Td) of 179 ℃ but also excellent FOMs with ???? = , ???? = , and ???? = 3 47 5 ???? ? . In addition, the highest of is achieved in (Pb0.94La0.04)(Zr0.86Ti0.14)O3 (x = 0.04) ceramic. These results demonstrate that the PLZT ceramics of x = 0.03 and 0.04 are promising candidates for pyroelectric applications.
关键词： ferroelectric/antiferroelectric material,energy harvesting,(Pb,La)(Zr,Ti)O3 ceramics,pyroelectric properties
更新于2025-09-23 15:23:52
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Large electric field-induced strain in ternary Bi0.5Na0.5TiO3-BaTiO3-Sr2MnSbO6 lead-free ceramics
摘要： The large electric-field-induced strain of Bi0.5Na0.5TiO3-BaTiO3 based ceramic make it a potential replacement for lead-based ferroelectrics in actuator applications. Herein, a ternary system (1-x)(Bi0.5Na0.5)0.935Ba0.065TiO3-xSr2MnSbO6 (BNBT6.5-xSMS) ceramic was fabricated using conventional solid-state reaction. It was found that the ferroelectric to relaxor phase transition temperature TF-R gradually shifted to lower temperature by increasing SMS contents. The ferroelectricity and piezoelectricity of BNBT6.5 were highly affected by trace amount of SMS doping. For composition BNBT6.5-0.003SMS, where TF-R was near room temperature, a large electric-field-induced unipolar strain of ~0.4% with high normalized strain (Smax/Emax) of 728 pm/V, which is comparable to lead-based ferroelectric/antiferroelectric ceramics, was achieved owing to the reversible electric-field-induced phase transition between a non-polar relaxor phase to a polar phase with long-range ferroelectric order.
关键词： electric-field-induced phase transition,ferroelectric,Lead-free ceramics,Bi0.5Na0.5TiO3
更新于2025-09-23 15:23:52
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The upconversion photoluminescence and temperature sensing abilities of Pb(Zn1/3Nb2/3)O3-9PbTiO3 crystals induced by Er3+/Yb3+ doping
摘要： Er3+/Yb3+-doped Pb(Zn1/3Nb2/3)O3-9PbTiO3 ferroelectric crystals were grown by the high-temperature solution method. The micromorphology, phase structure, and upconversion photoluminescence of obtained crystals were analyzed and investigated. As the results suggest, the crystals displayed typical lamellar growth and possessed a pure perovskite structure. Excited by a 980 nm laser, the characteristic upconversion (UC) emissions of Er3+ were observed at room temperature. The luminescence intensity improved with the increasing of excitation power and reached its maximum at 1056 mW. Two-photon process was demonstrated at lower power range. As the temperature increased from 213 to 493 K, the luminescence intensity weakened continuously. An apparent difference in variation trend between two thermally coupled levels (2H11/2 and 4S3/2) was also observed, which was ascribed to the redistribution of electrons at two levels at the heating process. Based on this dependence, the temperature sensing abilities were examined with the help of the fluorescence intensity ratio (FIR) technique. The absolute sensitivity SA increased in the measurement temperature range and its maximum of 0.0033 K-1 was obtained at 493 K. Moreover, low conversion from incident light into heat was also demonstrated, which indicates the feasibility for crystal luminescence at high power pumping. These results make Er3+/Yb3+-doped Pb(Zn1/3Nb2/3)O3-9PbTiO3 crystals become a promising candidate in optical devices and temperature sensors.
关键词： Two-photon process,Temperature sensing,FIR technique,Ferroelectric crystals,UC emissions
更新于2025-09-23 15:23:52
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Ferroelectric enhanced photoelectrochemical water splitting in BiFeO3/TiO2 composite photoanode
摘要： A facile sol-gel methodology was used to synthesize single-phase BiFeO3 (BFO) film on TiO2 photoanode to improve photoelectrochemical (PEC) water-splitting efficiency. The BFO films with controllable thickness induced a considerable ferroelectric polarization under bias voltage, which effectively tuned the electric band bending of BFO/TiO2. The photocurrent density of the as-prepared BFO-5/TiO2 could reach up to 11.25 mA/cm2, which is over 20 times higher than that of bare TiO2. Moreover, the positively poled BFO-5/TiO2 photoanode yielded a photocurrent density of 28.75 mA/cm2 at 1.5 V vs.SCE under AM 1.5G illumination. This work suggests that BFO/TiO2 with combined ferroelectric and semiconducting features could be a promising solution to improve PEC performance by concurrently promoting the light absorption and charge-separation and transportation properties.
关键词： BiFeO3,Ferroelectric polarization,Photoanode,Water-splitting
更新于2025-09-23 15:23:52
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Crystal structure, optical and electrical properties of metal-halide compound [C7H16N2][ZnCl4]
摘要： A new organic–inorganic hybrid compound [C7H16N2][ZnCl4] was synthesized by hydrothermal method and characterized by single-crystal X-ray diffraction, IR and Raman spectroscopy, optical absorption, differential scanning calorimetry and dielectric measurements. Single crystal diffraction results showed that [C7H16N2][ZnCl4] crystallizes in the monoclinic system, space group P21/c at room temperature. In the molecular arrangement, the tetrachlorozincate anions are connected to organic cations through N-H...Cl hydrogen bonds. The Raman and IR analyses confirm the presence of the organic groups and the anionic entities. UV–Visible absorption spectrum revealed the energy of the optical band gap. DSC measurements indicated that [C7H16N2][ZnCl4] undergoes three sequential phase transitions at 287, 338 and 356 K. The dielectric study proved the ferroelectric properties below the 338K and indicates their classical character for this compound. The analysis of Nyquist plots revealed the contribution of the bulk mechanism and the grain boundaries.
关键词： Phase transitions,Hybrid material,Crystal structure,Optical absorption,Ferroelectric properties,Conduction mechanism
更新于2025-09-23 15:23:52
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Fraction of Rare-Earth (Sm/Nd)-Lanthanum Ferrite-Based Perovskite Ferroelectric and Magnetic Nanopowders
摘要： Multiferroic compound, especially LaFeO3-based perovskite nanopowders that exhibit robust simultaneous ferromagnetism and ferroelectricity, are widely investigated and applied in different applications. In this work, we report the synthesis and characterization pertaining to fraction of rare-earth (Sm/Nd)-substituted lanthanum ferrite based perovskite nanopowders via solid-state technique. The multiferroic phenomenon is the fundamental approach to combine both the ferromagnetic and ferroelectric properties in a single system. Reduction in crystallite size, as well as some lattice distortion effects, are included to show the possibilities of tuning the lattice structure, electrical, optical as well as the magnetic properties which are closely connected to the ferroelectric behavior and magnetism. At room temperature, the ferroelectric behavior of La0.9(Sm/Nd)0.1FeO3 exhibiting a P-E hysteresis loop became more and more pronounced, indicating the electrical leakage is greatly reduced. The canted antiferromagnetic hysteresis loop shows that the rare-earth (Sm/Nd) ion can significantly affect the magnetic parameters of the materials.
关键词： Lanthanum ferrite,x-ray diffraction,optical and magnetic properties,solid-state reaction,ferroelectric,UV–Vis spectroscopy
更新于2025-09-23 15:23:52
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Spatial dual-electric fields for highly enhanced the solar water splitting of TiO2 nanotube arrays
摘要： Efficient charge separation is essential for improving the photo-conversion efficiency in both photocatalytic and photoelectrochemical (PEC) water splitting. Herein, we have demonstrated the selective spatial-construction of Au nanolayer and SrTiO3 nanocubes on inner and outer surfaces of TiO2 nanotubes for enhancing the charge separation and PEC activity. More specifically, the outer SrTiO3 nanocubes with a spontaneous ferroelectric polarization could effectively engineer the electrical band bending of TiO2 nanotubes, facilitating hole transfer to the electrode/electrolyte interface for water oxidation. Meanwhile, the inner Au nanolayer with a favorable plasmonic electric-field induced by the visible light promote charge separation and rapid electron transfer to the counter electrode for hydrogen generation. Benefiting from the spatial dual-electric fields, this SrTiO3/TiO2/Au ternary-photoanode exhibits a significantly enhanced photocurrent density of 2.11 mA cm?2 at 1.23 V (vs. RHE), which is nearly 3.5 times higher than that of the pristine TiO2 nanotube arrays. Additionally, a low onset potential (~ 0.17 VRHE) for water oxidation as well as an excellent PEC stability has also been achieved. These demonstrations may provide a new strategy toward the rational construction of highly efficient PEC water splitting systems.
关键词： TiO2 nanotube,Water splitting,Plasmonic,Ferroelectric
更新于2025-09-23 15:23:52
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Asymmetric strain: A critical role in domain evolution in (111) - Oriented ferroelectric films
摘要： Domain behavior of (111)- oriented perovskite ferroelectric films is significantly different from (001)-/(101)- oriented ones, resulting in enhancing property responses such as a superior susceptibility and a reduced coercive field. However, the domain structures and evolutions with the thickness of (111)-oriented ferroelectric films, which are crucial to further understand the distinctive properties, are still obscure. In this study, the ferroelectric domains of (111)- oriented PbTiO3 films are investigated by transmission electronic microscopy (TEM) and piezoresponse force microscopy (PFM). We identify the domain evolution with the film thicknesses under anisotropic strains imposed by the orthorhombic GdScO3 (101)O substrates. Contrast analysis and electron diffraction patterns reveal that only four ferroelectric variants evolve in PTO films: d2+, d2-, d3+ and d3-, with the polarization directions along [010], [010], [001] and [001], respectively. Two kinds of domain walls are formed: 'inclined' (011) domain walls for d2-/d3+ (d2+/d3-) domains, 'normal' (011) domain walls for d2+/d3- (d2-/d3+) domains. The width of periodically distributed d2+/d3+ (d2-/d3-) domains increases with film thickness following the square root rule. Aberration-corrected scanning transmission electronic microscopy demonstrates the lattice characteristics of domains in (111)- oriented PbTiO3 films are consistent with tetragonal ferroelectric domains. PFM studies reveal that both the out-of-plane and in-plane polarization components of d2-/d3+ (d2+/d3-) domains are non-identical, whereas the d2+/d3+ (d2-/d3-) domains possess uniform out-of-plane polarization component and non-uniform in-plane polarization component. This study discloses the domain structure in (111)-oriented tetragonal ferroelectric films under anisotropic strains and the association with the ferroelectric properties.
关键词： PbTiO3,Transmission electron microscopy,Ferroelectric,T,Perovskites,Piezoresponse force microscopy
更新于2025-09-23 15:23:52