采用草酸盐前驱体CaCu 3（TiO）4（C2 O 4）8？9H2O。通过湿化学分析、X射线衍射、FT-IR和TGA、DTA分析，证实了复合草酸盐前驱体的物相单一性。紫外-可见反射光谱和ESR光谱的CTO粉末表明，Cu（II）的协调变化从扭曲的八面体，近扁平四面体（压扁），以方形平面几何形状随着退火温度的升高。HRTEM图像显示，在纳米尺度的微观结构的演变是有关的化学制备的粉末试样的表面区域周围的Cu（II）的配位的变化。在近表面区域的颗粒，而正方形平面的CuO 4组是占主导地位的内部区域的纳米粒子的近扁平四面体的几何形状占主导地位。从草酸盐前体衍生的粉末具有优异的烧结性，导致在25 ° C下表现出高达40，000（1 kHz）的巨介电常数的高密度陶瓷，伴随着0.07的低介电损耗。
英文摘要：
A method of preparing the nanoparticles of CaCu3Ti4O12 (CCTO) with the crystallite size varying from 30 to 200 nm is optimized at a temperature as low as 680 1C from the exothermic thermal decomposition of an oxalate precursor, CaCu3(TiO)4(C2O4)8 ? 9H2O. The phase singularity of the complex oxalate precursor is confirmed by the wet chemical analyses, X-ray diffraction, FT-IR and TGA,DTA analyses. The UV Vis reflectance and ESR spectra of CCTO powders indicate that the Cu(II) coordination changes from distorted octahedra to nearly flattened tetrahedra (squashed) to square-planar geometry with increasing annealing temperature. The HRTEM images have revealed that the evolution of the microstructure in nanoscale is related to the change in Cu(II) coordination around the surface regions for the chemically prepared powder specimens. The nearly flattened tetrahedral geometry prevails for CuO4 in the near surface regions of the particles, whereas square-planar CuO4 groups are dominant in the interior regions of the nanoparticles. The powders derived from the oxalate precursor have excellent sinterability, resulting in high-density ceramics which exhibited giant dielectric constants upto 40,000 (1 kHz) at 25 1C, accompanied by low dielectric loss 0.07.
Pure phase and mixed phase TiO$_2$ nanoparticles have been produced using a pyrolytic method from a non-aqueous carboxylate precursor. The precursor was prepared by a multiphase cation exchange using pentanoic acid (C$_4$H$_9$COOH). The thermal stability, polymorph content, morphology, size distribution and surface region of the produced nanoparticles were studied by TGA/DSC, XRD, FTIR and TEM. High quality monodisperse nanoparticles have been produced in the size range from 7 to 27 nm. The nanoparticles showed room temperature ferromagnetism revealed by VSM within bound polaron model. The car…
Coalescence (or Growth) of tiny particles to larger particles has been an exciting and practical research topic in nanotechnology. This study deals with development of gold particles at varying precursor concentration in a custom-built setup. Under the tuned ratio of bipolar pulse OFF to ON time, tiny particles of different sizes and shapes develop depending on the amount of gold precursor. When compact monolayer assembly is formed on solution surface, nano energy in packet shapes bind gold atoms in own shape. Between 0.07 mM to 0.90 mM precursor concentration, tiny particles develop in both t…
Understanding and controlling properties of plasmon-induced hot carriers is a key step towards next-generation photovoltaic and photocatalytic devices. Here, we uncover a route to engineering hot-carrier generation rates of silver nanoparticles by designed embedding in dielectric host materials. Extending our recently established quantum-mechanical approach to describe the decay of quantized plasmons into hot carriers we capture both external screening by the nanoparticle environment and internal screening by silver d-electrons through an effective electron-electron interaction. We find that h…
At the nanometric scale, the synthesis of a random alloy (i.e. without phase segregation, whatever the composition) by chemical synthesis remains a not easy task, even for simple binary type systems. In this context, a unique approach based on the colloidal route is proposed enabling the synthesis of face-centred cubic and monodisperse bimetallic, trimetallic, tetrametallic and pentametallic nanoparticles with diameters around 5 nm as solid solutions. The Fe-Co-Ni-Pt-Ru alloy and its subsets are considered which is a challenging task as each element has fairly different physico-chemical proper…
Correlations of Spectroscopic and Dielectric Properties of Hafnia-Zirconia Nanoparticles
Frantsevich Institute for Problems in Materials Science of the National Academy of Sciences of Ukraine（乌克兰国家科学院弗拉琴科材料科学问题研究所）；Institute of Physics of the Czech Academy of Sciences（捷克科学院物理研究所）；Stockholm University（斯德哥尔摩大学）；Ye. O. Paton Institute of Materials Science and Welding, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”（乌克兰国立技术大学“伊戈尔·西科尔斯基基辅理工学院”叶·奥·帕顿材料与焊接研究所）；Oles Honchar Dnipro National University（阿列斯·洪恰尔第聂伯国立大学）；Institute of Physics of the National Academy of Sciences of Ukraine（乌克兰国家科学院物理研究所）
The possibility of controlling the domain structure in spherical nanoparticles of uniaxial and multiaxial ferroelectrics using a shell with tunable dielectric properties is studied in the framework of Landau-Ginzburg-Devonshire theory. Finite element modeling and analytical calculations are performed for Sn2P2S6 and BaTiO3 nanoparticles covered with high-k polymer, temperature dependent isotropic paraelectric strontium titanate, or anisotropic liquid crystal shells with a strongly temperature dependent dielectric permittivity tensor. It appeared that the tunable paraelectric shell with a tempe…
Correlations Between the Dielectric Properties, Domain Structure Morphology and Phase State of Bi1-xSmxFeO3 Nanoparticles
Institute of Physics, National Academy of Sciences of Ukraine（乌克兰国家科学院物理研究所）；Taras Shevchenko National University of Kyiv（基辅塔拉斯舍甫琴科国立大学）；Donetsk Institute for Physics and Engineering named after O.O. Galkin of the National Academy of Sciences of Ukraine（乌克兰国家科学院奥·奥·加尔金顿涅茨工程物理学研究所）；Stockholm University, Department of Chemistry（斯德哥尔摩大学化学系）；Ye. O. Paton Institute of Materials Science and Welding, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”（乌克兰伊戈尔·西科尔斯基基辅理工学院叶·奥·帕顿材料科学与焊接研究所）；Frantsevich Institute for Problems in Materials Science of the National Academy of Sciences of Ukraine（乌克兰国家科学院弗兰采维奇材料科学问题研究所）
Influence of BaTiO_3 nanoparticles on the anisotropy of the dielectric properties of nematic liquid crystal 5CB
Institute of Physics of the National Academy of Sciences of Ukraine（乌克兰国家科学院物理研究所）；Frantsevich Institute of Materials Science, the National Academy of Sciences of Ukraine（乌克兰国家科学院弗兰采维奇材料科学研究所）
Heat transfer from irradiated metallic nanoparticles is relevant to a broad array of applications ranging from water desalination to photoacoustics. The efficacy of such processes relies on the ability of these nanoparticles to absorb the pulsed illuminating light and to quickly transfer energy to the environment. Here we show that compared to homogeneous gold nanoparticles having the same size, gold-silica core-shell nanoparticles enable heat transfers to liquid water that are faster. We reach this conclusion by considering both analytical and numerical calculations. The key factor explaining…
Harnessing hot electrons and holes resulting from the decay of localized surface plasmons in nanomaterials has recently led to new devices for photovoltaics, photocatalysis and optoelectronics. Properties of hot carriers are highly tunable and in this work we investigate their dependence on the material, size and environment of spherical metallic nanoparticles. In particular, we carry out theoretical calculations of hot carrier generation rates and energy distributions for six different plasmonic materials (Na, K, Al, Cu, Ag and Au). The plasmon decay into hot electron-hole pairs is described …
We theoretically analyse the hybrid Mie-exciton optical modes arising from the strong coupling of excitons in organic dyes or transition-metal dichalcogenides with the Mie resonances of high-index dielectric nanoparticles. Detailed analytic calculations show that silicon--exciton core--shell nanoparticles are characterised by a richness of optical modes which can be tuned through nanoparticle dimensions to produce large anticrossings in the visible or near infrared, comparable to those obtained in plexcitonics. The complex magnetic-excitonic nature of these modes is understood through spectral…
We develop multipolar theory of nonlinear generation of entangled photons from subwavelength dielectric particles due to the spontaneous parametric downconversion. We demonstrate that optical excitation in resonance with the high-quality supercavity mode of the aluminum gallium arsenide (AlGaAs) nanodisk leads to a strong enhancement of generation of entangled photon pairs associated with electric and magnetic dipole modes. Our rigorous numerical results are corroborated by an analytical model, universally describing formation of high-$Q$ resonant states and dark states due to the interference…
Magnetodielectric study in SiO2-coated Fe3O4 nanoparticle compacts
研究了表面包覆SiO_2 $_{2}$的Fe $_{3}$ O $_{4}$磁性纳米粒子的介电性能。在高温下，磁场引起的介电常数和介电损耗的变化具有相反的符号和强烈的频率依赖性，这是由非本征磁介质耦合--Maxwell-Wagner效应和磁阻效应共同作用的结果。界面缺陷的存在导致测量中出现明显的迟滞现象。另一方面，在低温下的介电和磁性的强耦合矛盾的Maxwell-Wagner模型，建议内禀磁介电耦合。我们的观测结果与最近的极化开关测量结果相一致，证实了高损耗Fe $_{3}$ O $_{4}$中存在低温多铁态。这种核壳结构为实现低损耗的实用磁电材料提供了一条新的途径。
We consider a model of a nanocomposite based on non-interacting spherical single-domain ferroelectric nanoparticles of various sizes embedded in a dielectric matrix. The size distribution function of these nanoparticles is selected as a part of the Gaussian distribution from minimum to maximum radius (truncated normal distribution). For such nanocomposites, we calculate the dependences of the reversible part of the electric polarization, the electrocaloric temperature change, and the dielectric permittivity on the external electric field, which have the characteristic form of hysteresis loops.…
During the process of biomineralization, organisms utilize various biostrategies to enhance the mechanical durability of their skeletons. In this work, we establish that the presence of high-Mg nanoparticles embedded within lower Mg calcite matrices is a widespread strategy utilized by various organisms from different kingdoms and phyla to improve the mechanical properties of their high Mg calcite skeletons. We show that such phase separation and the formation of high-Mg nanoparticles are achieved through spinodal decomposition of an amorphous Mg calcite precursor. Such decomposition is indepe…
Recent developments in the area of resonant dielectric nanostructures has created attractive opportunities for the concentrating and manipulating light at the nanoscale and the establishment of new exciting field of all-dielectric nanophotonics. Transition metal dichalcogenides (TMDCs) with nanopatterned surfaces are especially promising for these tasks. Still, the fabrication of these structures requires sophisticated lithographic processes, drastically complicating application prospects. To bridge this gap and broaden the application scope of TMDC nanomaterials, we report here femtosecond la…
