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Cu2ZnGe(S1-xSe x)4 – The challenge to synthesize single phase material
摘要： The variation of the band gap energy in Cu2ZnGeSe4 and Cu2ZnGeS4 from 1.4 eV to 1.7 eV, which is controlled by different S/(S+Se) ratios renders the Cu2ZnGe(S1-xSex)4 solid solution an interesting material for the application in multi-junction solar cells. Nevertheless, this system has a certain complexity due to the existence of different polymorphs. Cu2ZnGeSe4 crystallizes in the tetragonal kesterite type structure, whereas Cu2ZnGeS4 may crystallize in the tetragonal stannite or the orthorhombic wurtz-stannite type structure, respectively. To gain deeper insights into this complex system a systematic study of the solid solution series Cu2ZnGe(S1-xSex)4 was performed using polycrystalline material prepared by solid state reaction. The chemical analysis performed by wavelength dispersive X-ray spectroscopy showed remarkable inhomogeneities with different quaternary phases co-existing within one sample. Additionally, a wide variety of binary and ternary secondary phases as well as elemental Ge was observed. The variety of secondary phases is higher in S-rich samples than in Se-rich samples of the solid solution. Thus, synthesis of Cu2ZnGe(S1-xSex)4 mixed crystals with off-stoichiometric composition is readily accompanied by the formation of various secondary phases making it a difficult task to obtain single phase material.
关键词： Wavelength dispersive X-ray spectroscopy,Solid state reaction,Polycrystalline powders,Chalcogenides,Secondary phases,Copper zinc germanium selenide,Copper zinc germanium sulfide
更新于2025-09-11 14:15:04
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Higher permittivity of Ni-doped Lead Zirconate Titanate, Pb[(Zr0.52Ti0.48)(1-x) Nix]O3, ceramics
摘要： The paper reports highest obtained dielectric constant for Ni-doped Lead Zirconate Titanate [PZT, Pb(Zr0.52Ti0.48)O3] ceramics. The Ni-doped PZT ceramic pellets were prepared via conventional solid-state reaction method with Ni content chosen in the range 0-20 at.%. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were employed to investigate the crystal structure of the prepared ceramics. The X-ray diffraction analysis indicated that the ceramic pellets had crystallized into tetragonal perovskite structure. A minute displacement of XRD peaks was detected in the diffraction spectra of Ni-doped PZT which when examined by size-strain plot (SSP) method revealed presence of homogenous strain that decreased with increase in concentration of Ni. In FTIR the maximum absorption at 597 cm-1, 608 cm-1, 611 cm-1, 605 and 613 cm-1 for Ni = 0, 5, 10, 15 and 20 at.%, respectively, confirmed the formation of perovskite structure in all the compositions and the slight shift suggests decrease in cell size on doping. The values of dielectric constant (ε￠) & tand as a function of frequency and temperature were measured for the prepared ceramics and it revealed highest ever reported dielectric constant for Ni - doped PZT with Ni = 5 at.%. The dielectric variation with temperature exhibited a diffused type ferroelectric–paraelectric phase transition for the doped samples. Also, the maximum dielectric constant value (??max) decreased with an increase in doping concentration of Ni while the phase transition temperature increased with increase in doping concentration. The estimated activation energy of different compositions was found to increase from 0.057 to 0.068 eV for x = 0.00 to x = 0.20 in ferroelectric phase. The piezoelectric, ferroelectric and magnetic properties were also investigated.
关键词： Piezoelectric ceramics,Dielectric,solid-state reaction,Ni-doping
更新于2025-09-10 09:29:36
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Synthesis and multimethodological characterization of neodymium substituted nickel tungstates and molybdates solid solution Ni Ndx (W,Mo)O4, (0?≤?x?≤?0.2)
摘要： New series of neodymium substituted nickel tungstates and molybdates NiNdxM’O4 (M’=W,Mo and x=0%, 10%, 20%) were synthesized by standard solid state route at high temperature T=1000°C.These materials, were characterized by powder X-Ray diffraction technique (XRD), which confirmed that both series of tungstates and molybdates crystallized in monoclinic structure with space groups(P2/c, C2/m) respectively and behaved as a quasi-ideal solid solution. Scanning Electron Microscopy (SEM) experiments showed the presence of grains with irregular sizes developed within larger aggregations, while EDS semi-quantitative analyses confirmed the nominal compositions for all the phases.Active vibration modes were investigated by Fourier Transform InfraRed (FTIR) and Raman techniques, the group theoretical calculation predicted 36 vibrational modes. The presence of characteristic frequencies assigned to components ?1 and ?3 confirmed the existence of WO6 and MoO6 polyhedra in the structures, non-vibrational bands appearing in Raman spectra were attributed to laser-excited luminescence of neodymium element.
关键词： solid state reaction,vibrational properties,neodymium,nickel tungstates,X-ray diffraction,nickel molybdates
更新于2025-09-10 09:29:36
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Solid-State Preparation, Structural Characterization, Physical Properties and Theoretical Studies of a Series of Novel Rare-earth Metal-Chalcogenides with Unprecedented Closed Cavities
摘要： Multinary rare-earth metal-chalcogenides have aroused great concern owing to their special structure characteristics and diverse physical functions. In this work, five novel rare-earth chalcogenides adopt the formula Cs2[RE8InS14] (where RE = Ho–Lu), has been obtained by the elementals mixture in CsCl flux at 1273 K. They are isotype and belong to the orthorhombic Cmca (no. 64) [a = 15.711(7)–15.385(2) ?, b = 22.232(2)–21.786(2) ?, c = 15.483(5)–15.244(2) ?, V = 5408.4(4)–5130.1(7) ?3 and Z = 8], exhibiting a dense 3D [RE8InS14] framework consisting of RES6 octahedron and discrete InS4 tetrahedron. The large closed-cavities Cs4@S26 are far apart embedded within the network along bc-plane, which is discovered for the first time. The band gaps from 2.45 to 2.72 eV for Cs2[RE8InS14] were deduced from the UV?Vis–NIR spectroscopy based on the Kubelka-Munk function. Magnetic test indicates that the Cs2[RE8InS14] (RE = Ho–Yb) compounds possess para-magnetism above 50K. In addition, the solid-state preparation, structural characterization, theoretical studies together with a structure–G/H ratio relationship (G = atomic number of guest metals; H = atomic number of host metals) are also presented.
关键词： crystal structure,solid-state reaction,magnetic properties,large closed cavities,rare-earth metal-chalcogenides
更新于2025-09-10 09:29:36
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Photoluminescence characteristics of Pr3+ doped PbGdB7O13 as a new red emitting phosphor
摘要： A red phosphor Pr3+ doped PbGdB7O13 was synthesized by high temperature solid state reaction. The effect of Pr3+ doped concentration on the luminescent properties of the phosphor was investigated. The emission spectrum includes an apex at about 607 nm, corresponding to the 3P0→3H6 transition of the Pr3+ ion activator. For PbGd1-xB7O13:xPr3+, the emission peak intensity first increases with the increase of Pr3+ concentration, and reaches the maximum when the Pr3+ concentration is 0.02, and then decreases with the increase of Pr3+ concentration. The CIE coordinates of the PbGdB7O13:0.02Pr3+ phosphor was calculated to be (0.6332, 0.3651), falling into the red color. Therefore, there is a potential application on display, indication or illumination.
关键词： Photoluminescence,High temperature solid state reaction,CIE,Borate
更新于2025-09-10 09:29:36
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Enhanced dielectric properties of BaTiO3 ceramics with cerium doping, manganese doping and Ce-Mn co-doping
摘要： Ba1?xCexTi1?yMnyO3 (where x and y varies from 0.00 to 0.03) ceramic samples are synthesized by conventional solid state reaction technique. The samples are sintered at 1473 K for 4 h. The grain size is observed to increase with increasing dopant and co-dopant concentration. The X-ray diffraction confirmed the cubic phase of these BaTiO3-based ceramics with a small amount of secondary phase. The current density shows a nearly linear relationship with voltage, and the AC resistivity of the samples is observed to decrease with increasing frequency and doping concentration. The dielectric constant and dielectric loss were observed to decrease with frequency in the lower frequency range (0.2–10 kHz), but remained almost the same at the high-frequency region (>10 kHz). Though Ce-doped samples shows better dielectric properties than Mn-doped samples, the Ce-Mn co-doped samples, having improved their dielectric properties, can be used to fabricate different optoelectric devices.
关键词： resistivity,SEM,solid state reaction,dielectric properties,XRD,grain size
更新于2025-09-09 09:28:46
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Sintering evaluation of doped lanthanum gallate based on thermodilatometry
摘要： The sintering behavior of La0.9Sr0.1Ga0.8Mg0.2O3-δ oxide-ion conductor was systematically investigated by thermodilatometry. The shrinkage data obtained with heating rates of 4, 7, 10 and 12oC.min-1 were analyzed by the constant rate of heating model and by construction of the master sintering curve. Validation of the master sintering curve was carried out by measurements of density in conventionally sintered specimens. Slight anisotropy of shrinkage data was found and changes to the basic equation of density was proposed to account for this effect. Plotting the data determined by the constant rate of heating model versus density allowed an easy identification of the density range of constant activation energy. The activation energy (865 kJ.mol-1) obtained from the master sintering curve correlates quite well with that (874 kJ.mol-1) obtained by the constant rate of heating model.
关键词： A. Sintering,A. Powders: solid state reaction,E. Fuel cells,D. Perovskites
更新于2025-09-09 09:28:46
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Dielectric, electrical and impedance study of single perovskite Pb(Ni1/3Mn1/3W1/3)O3
摘要： A multiferroic material Pb(Ni1/3Mn1/3W1/3)O3 with ferroelectric and ferromagnetic properties at room temperature is designed for multifunctional applications. A orthorhombic perovskite crystal structure has been assigned for the present perovskite according to the X-ray diffraction patterns. At 1 kHz, dielectric constant (er) increases from 1655 at 298 K to its ?rst maximum 3514 at 457 K referred as magnetic transition. The high values of er in the low frequency range show better dispersion, and with the increase in frequency, a gradual decrease in the er values was observed. The contribution of grain and/or electrode/interface effects in the resistive/capacitive properties was ascertained by the Nyquist plots. An equivalent circuit has been suggested consisting of resistive and capacitive components (R, C, Q) estimates the bulk (grain) and grain boundary resistance and capacitance. The activation energy was found to be greater than 0.2 eV, supporting the conduction mechanism due to hopping of charge carriers.
关键词： Solid-state reaction,Multiferroic material,Dielectric response,Electrochemical impedance spectroscopy,Ceramics
更新于2025-09-09 09:28:46
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Influence of compositional ratio K/Na on structure and piezoelectric properties in [(Na1?xKx)0.5Bi0.5]Ti0.985Ta0.015O3 ceramics
摘要： [(Na1-xKx)0.5Bi0.5]Ti0.985Ta0.015O3 (abbreviated as Ta-NK100x) lead-free ceramics with good piezoelectric properties were prepared using a solid-state reaction method. The structure and electrical properties of Ta-NK100x had been systemically investigated. The highest bipolar strain of 0.458% and the unipolar strain 0.448% are achieved at x = 0.18 at 60 kV/cm. Meanwhile, the corresponding normalized strain d*33 reaches 747 pm/V. In addition, the unipolar strain of the poled Ta-NK18 increases to 0.537%, and corresponding d*33 increases slightly to 894.5 pm/V at 60 kV/cm. The electric-field-induced phase transition between ferroelectric and relaxor is found to play a dominant role in the origin of the large strain. Moreover, the strain behavior remains stable within 105 switching cycles which indicating the prepared ceramics are promising candidates for actuators and stress sensors.
关键词： ferroelectric,relaxor,solid-state reaction,piezoelectric properties,lead-free ceramics
更新于2025-09-04 15:30:14
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Mg and N co-doped CuCrO <sub/>2</sub> : A record breaking p-type TCO
摘要： We prepare CuCrO2 thin ?lms with magnesium and nitrogen dopants. The solid state reaction method is employed to produce CuCrO2 targets with three different concentrations of Mg (0%, 2.5%, and 5%). The targets are used in an RF sputtering system to prepare thin ?lms in the presence of N2 as the reactive gas. In this manner, Mg and N atoms, respectively, replace Cr and O sites in the CuCrO2 structure and enhance the electrical and optical properties of the host material. This cationic-anionic substitution yields a superior hole transport and results in an increased conductivity of (cid:2)278 S cm(cid:3)1 which is considered as a record for p-type conductivity in transparent conducting oxides. Moreover, the co-doped CuCrO2 demonstrates a bandgap of 3.52 eV and a transmittance of about 69% in the visible region.
关键词： transparent conducting oxides,RF sputtering,solid state reaction,Mg and N co-doped CuCrO2,p-type TCO
更新于2025-09-04 15:30:14