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High-efficiency synthesis of high-performance K0.5Na0.5NbO3 ceramics
摘要： Pure (K0.5Na0.5)NbO3 (KNN) ceramics with high density, fine and uniform-size grains were prepared by mechanochemical activation-assisted process. The time of synthesis is only 100 min, which is 72% - 93% shorter than the 6-24h of the conventional solid-state method. Compared to samples prepared by conventional solid-state method, both the microstructure evolvement and electric properties were explored in detail. Results show the electric properties was significantly improved. Moreover, the dielectric and ferroelectric properties of obtained KNN ceramics exhibit strong dependence on the crystal size of the initial powders. The optimized ceramics HKNN100 showed a quite high energy storage performance, i.e., large electric energy storage density (Wtol=1.612 J/cm3) and recoverable energy storage density (Wrec=0.431 J/cm3), which can be mainly ascribed to the large dielectric breakdown strength (DBS=110 kV/cm). Our works demonstrated that mechanochemical activation-assisted method possesses advantages for high-efficiency preparation of KNN or KNN-based ceramics.
关键词： Dielectric properties,Ferroelectricity,(K0.5Na0.5)NbO3 Ceramics,Mechanochemical activation,Microstructure
更新于2025-11-14 17:04:02
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Phosphotellurite glass and glass-ceramics with high TeO <sub/>2</sub> content: thermal, structural and optical properties
摘要： Phosphotellurite based glasses have interesting features such as low characteristic temperatures, large glass forming ability, high thermal stability against crystallization and broad transparency window from ultraviolet (UV) to near-infrared (NIR), which makes them promising materials for photonic applications. In this work, phosphotellurite binary glasses, having composition (100 – x) TeO2–x Ba(PO3)2 with x varying from 1 to 20 mol %, were synthesized by the conventional melt-quenching method in covered gold crucibles under air. Optical, physical and structural properties of the new glass samples were investigated by differential scanning calorimetry, X-rays diffraction, Raman spectroscopy, transmission electron microscopy, linear optical absorption from UV to NIR, IR transmittance, and optical limiting experiments. Transparent glass-ceramics in the visible range were obtained for phosphotellurite samples containing 2, 4 and 6 mol % of Ba(PO3)2 and the phase crystallization was investigated through Rietveld analysis and transmission electron microscopy. The incorporation of Ba(PO3)2 into the TeO2 network drastically increases the thermal stability against devitrification and helps to shift the infrared multiphonon absorption edge to longer wavelengths. Nonlinear measurements performed with a picosecond laser at 532 nm indicate large effective nonlinear absorption coefficients for all samples. In summary, the dependence of the spectroscopic properties on the samples’ compositions revealed a promising transparent glass and glass-ceramics for photonic applications.
关键词： transparent glass-ceramics,phosphotellurite glass,optical properties,nonlinear optical response
更新于2025-11-14 17:03:37
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The effect of second phase La0.67TiO2.87 on the phase structure and impedance spectroscopy of La2Ti2(1 + x)O7 piezoelectric ceramics
摘要： The Ti excess La2Ti2 (1 + x) O7 (x = 0, 0.005, 0.01, 0.02, 0.05, 0.1) piezoelectric ceramics have been prepared by sol-gel technology and solid state synthesis method. Through refinement analysis, the phase structure of the ceramics varies with Ti content. Most monoclinic phase (~ 93 %) and a handful of orthogonal phase (~ 7 %) coexist in La2Ti2 (1 + 0) O7 ceramics. Pure monoclinic phase La2Ti2O7 with space group P21 appears in La2Ti2 (1 + 0.005) O7 and La2Ti2 (1 + 0.01) O7 ceramics. Monoclinic phase La2Ti2 O7 and a certain proportion of tetragonal phase La0.67TiO2.87 coexist in La2Ti2 (1 + 0.02) O7, La2Ti2 (1 + 0.05) O7 and Ti2 (1 + 0.1) O7 ceramics. With the excess of Ti content, the monoclinic phase ratio and distortion angles in a-b projection plane of the ceramics increase first and then decrease, which is consistent with the variation tendency of piezoelectric constant d33. The excellent piezoelectric constant for Ti2 (1 + 0.01) O7 ceramics is 2.8 pC/N. Impedance analysis shows that the conductive mechanisms of all samples include both grain and grain boundary conductivity at temperature range T ≥ 500 ℃. The formation of tetragonal phase La0.67TiO2.87 derives from Ti excess in pure monoclinic phase La2Ti2O7. The existence of tetragonal phase La0.67TiO2.87 can obviously increase the capacitance of ceramics at x ≥ 0.05. All prepared piezoelectric La2Ti2 (1 + x) O7 ceramics have highly frequency stability and are candidates for ultrahigh temperature piezoelectric application.
关键词： La2Ti2(1 + x)O7 ceramics,phase structure,impedance spectroscopy
更新于2025-11-14 15:27:09
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Eu and Dy doped borophosphosilicate glass-ceramics for near ultraviolet based light-emitting diode applications
摘要： The Eu and Dy doped borophosphosilicate glass-ceramics prepared using melt quenching technique are investigated for light-emitting diode applications. The X-ray diffraction results show that the precipitation of AlPO4 crystals in glass matrix occurred during the melt quenching process, leading to the formation of glass-ceramics. The content of AlPO4 crystals depends on the B2O3/P2O5 relative content in glass matrix composition. The spontaneous conversion of Eu3+ to Eu2+ takes place in the as-obtained glass-ceramics without using reducing atmosphere during the preparation process. The conversion extent of Eu3+ to Eu2+, optical properties and structure of the as-obtained materials are related to the B2O3/P2O5 relative content. The Eu/Dy co-doped borophosphosilicate glass-ceramics display the emission bands in the blue, yellow, and red light regions and their combinations generate near white light-emission. In addition, the tunable light emission can be realized by changing the concentration of Eu and B2O3/P2O5 relative content. The as-developed Eu and Dy doped borophosphosilicate glass-ceramics show promising prospects in light-emitting diode applications.
关键词： Rare earth,Luminescence,Light-emitting diode,Borophosphosilicate glass-ceramics
更新于2025-11-14 15:23:50
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Tuning Ferroelectric, Dielectric, and Magnetic Properties of BiFeO <sub/>3</sub> Ceramics by Ca and Pb Co-Doping
摘要： Effects of Ca/Pb co-doping on structure, ferroelectric, dielectric, and magnetic properties of BiFeO3 ceramics are investigated. A structure transition from a rhombohedral phase (space group R3c) to a cubic phase (space group Pm3m) with the increment of Ca/Pb concentration is revealed by X-ray diffraction and Raman spectra. In order to compensate the valence change caused by Ca2+ dopant, Pb ions present tetravalent state under the existence of Ca ions. The room-temperature ferroelectric behavior depends upon Ca/Pb co-doping and the structural transition in BiFeO3 ceramics. Meanwhile, the variation of the dielectric loss tangent in the frequency range of 102–107 Hz and the leakage current at room temperature illustrate that Ca/Pb co-doping increases resistivity and reduces leakage current. Compared with that of Sr/Pb co-doping, the co-doping of Ca/Pb has improved the leakage current by two orders of magnitude, besides further increasing the ferroelectric polarization and dielectric properties under the same co-doping concentration. In addition, enhanced ferromagnetism is observed with the increase of Ca/Pb content, which can be attributed to the effective suppression of spiral cycloidal spin structure and spin canting resulting from the structural transition.
关键词： BiFeO3,ferroelectricity,co-doping,dielectricity,ceramics,magnetism
更新于2025-09-23 15:23:52
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Polarization and acoustic properties of barium-modified lead-free potassium–sodium niobate ceramics
摘要： Results of polarization and polarization switching in samples prepared by solid phase synthesis of the (1-х)(K0.5Na0.5)(Nb0.93Sb0.07)O3–xBaTiO3 + 0.5mol%MnO2 system at x = 0.01, 0.02, and 0.04 (KNNS7–xBT) studied over a wide range of temperatures are reported. The observed features of the dielectric nonlinearity at the ferroelectric and structural phase transitions in the materials are described. The dielectric response data of the samples of different contents of the admixture in the KNNS7–xВT ceramics are compared with the behaviour of their elastic properties.
关键词： dielectric permittivity,polarization,solid solutions,elastic properties,relaxors,ferroelectrics,ceramics
更新于2025-09-23 15:23:52
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Analogous Anti-Ferroelectricity in Y2O3-Coated (Pb0.92Sr0.05La0.02)(Zr0.7Sn0.25Ti0.05)O3 Ceramics and Their Energy-Storage Performance
摘要： Antiferroelectric analogous (Pb0.92Sr0.05La0.02)(Zr0.7Sn0.25Ti0.05)O3 (PSLZSnT) ceramics were prepared by the solid-state sintering method by introducing a Y2O3-coating via the self-combustion method. The synthesized Y2O3-doped PSLZSnT ceramics present pseudo-cubic structure and rather uniform microstructural morphology accompanied by relatively small grain size. Excellent energy-storage performance is obtained in the Y2O3-doped PSLZSnT ceramics, in which the value of the energy-storage density presents a linearly increasing trend within the electric field measurement range. Such excellent performance is considered as relating to the rather pure perovskite structure, high relative density accompanied by relatively small grain size, and the antiferroelectric-like polarization-electric field behavior.
关键词： oxide doping,self-combustion method,energy-storage density,perovskite structure,PSLZSnT antiferroelectric-like ceramics
更新于2025-09-23 15:23:52
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Characterization, optical and luminescence features of cobalt ions in multi-component PbO Al2O3TeO2GeO2SiO2 glass ceramics
摘要： Glass ceramics of the composition PbOeAl2O3eTeO2eGeO2eSiO2 doped with CoO (ranging between 0 and 1.0 mol %) were prepared by melt quenching technique followed by heat treatment. The techniques such as XRD, SEM, EDS and DTA were employed for the characterization of the prepared samples. Conventional spectroscopic studies viz., optical absorption, photoluminescence, FTIR and Raman were also performed on these samples. The optical absorption spectra of the titled glass ceramics exhibited two principal absorption bands, one at about 594 nm and the second one consisting of multiplets with the meta centre at about 1455 nm ascribed to the 4A2 (4F) → 4T1 (4P) and 4A2 (4F) → 4T1 (4F) transitions of tetrahedrally coordinated Co2+ ions, respectively. Besides these, the spectra also exhibited two feeble bands at about 532 and 643 nm which are the characteristics of octahedrally coordinated Co2+ and Co3+ ions, respectively. Using Tanabe Sugano diagram the crystal field splitting parameter Dq, Racah parameters B, C and nephelauxetic ratio, β were evaluated for Co2+ ions. The photoluminescence spectra of the titled glass ceramics have exhibited two broad emission bands at 628 and 870 nm ascribed to 4T1 (4P) → 4A2 (4F) and 4T1 (4P) → 4T2 (4F) tetrahedral transitions of Co2+ ions, respectively. FTIR and Raman spectra of the titled samples exhibited various asymmetrical and symmetrical vibrational bands due to viz., silicate, germanate, PbO4, PbO6, AlO6, TeO4, TeO3 and CoIIIeO vibrations in the glass ceramic matrix. The spectroscopic investigations on the titled glass ceramics have revealed that if CoO is present in small quantities the cobalt ions predominantly occupy the octahedral sites in the glass network, whereas the tetrahedrally coordinated Co2+ ions are found to increase if the concentration of nucleating agent CoO is gradually increased up to 1.0 mol%. As a result the degree of depolymerization of the glass network decreases which in turn enhances its rigidity with increasing the concentration of nucleating agent CoO. From these investigations we report that the glass ceramics doped with 1.0 mol% of CoO are suitable for insulating devices as well as for photonic devices.
关键词： Photoluminescence,Raman spectra,XRD,Multi-component glass ceramics,SEM,Optical absorption,Cobalt ions
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