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Due to the boom of the electronic information industry, dielectric ceramic materials are widely applied in passive components such as multilayer ceramic capacitors. In this article, Y2/3Cu3Ti4O12–TiO2 composite ceramics with outstanding dielectric properties (εr = 2.29 × 106 at 20 Hz, εr = 4.49×105 at 1 kHz) were successfully prepared by hydrothermal and in situ solid‐state methods. The minimum dielectric loss value (at 1 kHz) of the obtained composite ceramics is about 0.57. The experimental results show that Y2/3Cu3Ti4O12 has a composite perovskite structure with cation vacancies, which causes internal electron‐pinned defect‐dipole, and the easy entry of excessive titanium ions to produce donor defects. Meanwhile, the heterogeneous grains with a pomegranate‐like microstructure were observed in the prepared composite ceramics, and interfacial polarization between subgrain boundaries was substantiated by impedance analysis. The abundant weakly trapped electrons and more polarized interfaces formed by grain and subgrain boundaries are the primary sources of the excellent dielectric properties of composite ceramics. [ABSTRACT FROM AUTHOR]

The triangulated irregular network (TIN) clipping algorithm is one of the vital algorithms for the digital mining design of opencast coal mines based on the geological digital elevation model (DEM) described by TIN. This paper gives a precise TIN clipping algorithm applied in the digital mining design of the opencast coal mine. To improve the algorithm's efficiency, a spatial grid index is built and utilized to embed the Clipping Polygon (CP) into the Clipped TIN (CTIN) by interpolating the CP's vertices' elevation and solving the intersections of the CP and the CTIN. After that, the topology of the triangles situated within (outside of) the CP is reconstructed, and then the boundary polygon of those triangles is obtained based on the reconstructed topology. Finally, a new boundary TIN between the CP and the boundary polygon of the triangles situated within (outside of) the CP is generated by applying the one-time edge-prior constrained Delaunay triangulation (CDT) growth algorithm, and the TIN to be clipped out is separated from the CTIN by topology modification. At that point, CTIN clipping is accomplished with the local details remaining. The algorithm has been programmed in C# and.NET. Additionally, it is also applied to the opencast coal mine digital mining design practice, and it is robust and highly efficient. [ABSTRACT FROM AUTHOR]

The CCTO/SnO2 composite ceramics were fabricated by sintering at 1040°C for 8 h. The FESEM found that the grain size decreased sharply when the SnO2 addition amount reached 15 mol%. The dielectric spectra confirmed that the addition of SnO2 helps to improve the dielectric properties of CCTO, and the dielectric constants of 20 mol% SnO2 reached 1.74 × 106 and 4.2 × 105 at 20 Hz and 1 kHz, respectively. XPS found the coexistence of Cu+ and Ti3+ related to the defect compensation mechanism. Impedance spectroscopy confirms that the addition of SnO2 helps to improve the semiconductivity of CCTO, thereby enhancing the dielectric properties of CCTO. [ABSTRACT FROM AUTHOR]

CaCu3Ti4O12/CaTiO3/TiO2 (CCTO/CTO/TiO2) composite ceramics were fabricated by an in situ route and sintered at 1040 °C for 8 h. The micrographs of FESEM show that the ceramics are dense and delicate, with an average particle size of about 0.9–1.4 μm. XPS found the existence of Cu+ and Ti3+, which was caused by the charge compensation reaction derived from part of Ti4+ ions entering the V″Cu to form the donor Ti · · Cu . The impedance analysis shows that excessive CTO and TiO2 significantly reduce the grain boundary resistance of CCTO/CTO/TiO2 ceramics. Furthermore, it can be found that due to excessive CTO, TiO2 reacts with segregated CuO to form CCTO again and reduce the CuO concentration at the grain boundaries. Therefore, this significantly reduces the grain boundary width, resulting in a colossal dielectric constant of 9.0 × 105 at 30 Hz. [ABSTRACT FROM AUTHOR]

In this work, CaTiO3-based particles covered with nano-sized CuO and TiO2 particles were obtained by the hydrothermal method (CuO/CaTiO3 (molar ratio) = 0.2 and TiO2/CaTiO3 (molar ratio) = 0, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30, respectively). The dense ceramics with a colossal dielectric constant at room temperature (εr > 1.2 × 105 at 20 Hz, εr > 7 × 103 at 1 kHz) and good temperature stability was obtained by microwave sintering at 1400 °C. The crystal structure, morphology, dielectric properties, impedance, and oxidation state of the ceramics were systematically analyzed. According to the results, the weak-trapped electrons are derived from defects and in the semiconducting CaCu3Ti4O12 regions. A large amount of nano-sized CuO and TiO2 covered on the surface of CaTiO3 blocks the transfer of substances between grains, resulting in small ceramic grains. Simultaneously, the synthesized CaCu3Ti4O12 and CaTiO3 form a structure similar to nano-scale barrier layer capacitance (NBLC), and it can be proved by impedance analysis. The results show that a large number of weak-trapped electrons, smaller crystal grains and a structure similar to NBLC are the possible main reasons for the colossal permittivity. [ABSTRACT FROM AUTHOR]

Abstract: CaCu3Ti4O12 nano-sized powders were successfully prepared by sol–gel technique and calcination at 600–900°C. The thermal decomposition process, phase structures and morphology of synthesized powders were characterized by IR, DSC-TG, XRD, TEM, respectively. It was found that the main weight-loss and decomposition of precursors occurred below 450°C and the complex perovskite phase appeared when the calcination temperature was higher than 700°C. Using above synthesized powders as starting materials, CCTO-based ceramics with excellent dielectric properties (ɛ 25 =5.9×104, tan δ =0.06 at 1.0kHz) were prepared by sintering at 1125°C. According to the results, a conduction mechanism was proposed to explain the origin of giant dielectric constant in CCTO system. [Copyright &y& Elsevier]

The thermal sensitivities of SrTiO3-based ferroelectric ceramics and the dielectric properties have been investigated. Strontium–lead titanate ceramics with variable NTCR–PTCR composite effect were prepared by controlling Pb concentration of the grain boundaries. It was efficient for lowering the room temperature resistivity (ρRT) and weakening the negative temperature coefficient of resistance (NTCR) effect of (Sr, Pb)TiO3 ceramics by adding a small amount of excess PbO. A transformation of thermal sensitivity from the positive temperature coefficient of resistance (PTCR) to NTCR–PTCR characteristics was also observed after a heating treatment process, showing the NTCR–PTCR composite effects of (Sr, Pb)TiO3 semiconducting ceramics were closely related to the variation of Pb concentration at the grain boundaries. The conduction mechanism was proposed to reasonably explain the NTCR–PTCR composite effect of (Sr, Pb)TiO3 semiconducting ceramics. SrTiO3 ceramics capacitors were fabricated by using La2O3–CuO–PbO as dopants. It exhibited a high dielectric constant with stable temperature characteristics. It was found that PbO addition benefited to increasing the dielectric constant and CuO addition mainly segregated at the grain boundaries to form the isolation layers. The relationships between the microstructures and the dielectric properties of SrTiO3–La2O3–CuO–PbO system were discussed. [Copyright &y& Elsevier]

(Y, Mn) co-doped Sr0.5Pb0.5TiO3 ceramics were fabricated by solid state reaction method. The samples’ room temperature resistivities increase and their negative temperature coefficient of resistance (NTCR)–positive temperature coefficient of resistance (PTCR) composite effects become strong with increasing Mn concentration. The investigations of scanning electron microscope and complex impedance spectra show that Mn addition confines the grain growth and increases the grain boundary resistance. In addition, electron paramagnetic resonance spectra confirm that the Mn impurities are in forms of high valence below the Curie temperature (Tc) and divalent Mn2+ cations appear above Tc. It is assumed that partial Mn cations can trap the electrons and be reduced to divalent Mn2+ cations during phase transition, which benefits to improving the PTCR effect of (Sr, Pb)TiO3-based thermistors. And the NTCR effect below Tc should be closely related to the acceptor defects in the grain boundary layers. [Copyright &y& Elsevier]

Lanthanum-doped Sr0.5Pb0.5TiO3 semiconducting ceramics were prepared by the solid state reaction technique with excess PbO additive. Samples'' resistivities rise about 5 orders of magnitude above the Curie temperature (Tc≈115 °C) and their negative temperature coefficient of resistivity (NTCR) increases with an increase of the sintering temperature. The crystalline structure, microstructure and compositional distribution were investigated using XRD, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with X-ray energy dispersive analyses (EDAX), respectively. The distribution of Pb, Sr and Ti in the grain boundary layer has been shown to be similar to that in the grain interior. It is assumed that the PbO additive compensates Pb loss and keeps the Pb/Ti ratio stable in the grain boundary layers, which results in the low room temperature resistivity and weak NTCR effects. [Copyright &y& Elsevier]

Y-doped Sr0.5Pb0.5TiO3 semiconducting ceramics were fabricated by adding excess PbO and controlling the sintering conditions. Their room temperature resistivity (ρRT) is 101 Ω cm and there is a jump of about five orders of magnitude in resistivity, showing the positive temperature coefficient of resistance (PTCR) effect. Adding Ag+ increases both the ρRT and the PTCR effect. Ag metal particles were observed to segregate in the 1.0 mol% Ag+-doped composition. The influences of excess PbO and Ag+ on the electrical properties of (Sr, Pb)TiO3-based semiconducting ceramics were discussed. [Copyright &y& Elsevier]