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Abstract: The insulation resistance (IR) and the electrical endurance of Y-acceptor doped (Ba,Ca)(Ti,Zr)O3 ceramics, fired in reducing atmospheres, are significantly improved by a re-oxidation treatment. This effect has been studied by means of impedance spectroscopy (IS). Insulating grain boundary barrier layers were detected also without interaction with Ni-inner electrodes, as they are applied in multilayer ceramic capacitors (MLCCs). In moist firing atmospheres H2O vapor was found to react with oxygen vacancies, forming positively charged hydroxyl defects on regular oxygen sites in the crystal lattice. Hopping of protonic defects is supposed to raise the ionic conductivity. Re-oxidation in dry gas mixtures of O2 and N2, however, desorbs water from the dielectric material and improves the IR. DC-field stress heavily degrades the grain boundary barriers. Protons in the dielectric material largely accelerate the electrical degradation. Hydroxyl defects are also considered to be responsible for alterations of the dielectric temperature characteristics at the Curie point. [Copyright &y& Elsevier]

Abstract: High temperature heat treatment of internal Ni electrode and BaTiO3 dielectric layers is one of the important steps in the sintering process of multilayer ceramic capacitors (MLCCs). In this study, microstructural analysis of partially oxidized Ni electrode in dielectric layers was conducted. Sub-micrometric NiO scales were found along the interface of Ni/BaTiO3. In addition, the capacitance, dielectric loss, and isolation resistances of the samples after post-treatment in N2 atmosphere at 1000°C for 0–8h were analyzed. A detailed analysis on the NiO and the discussion on the formation mechanism of NiO are presented in this paper. [Copyright &y& Elsevier]

Abstract: The growth of GaN epilayers on AlN/Si (111) templates with thin nonlinearly composition-graded Al x Ga1−x N interlayers via metal-organic chemical vapor deposition (MOCVD) is reported in this work. The composition-graded Al x Ga1−x N interlayer was achieved by simply changing the growth condition of AlN to that of GaN layers during a fixed time. The surface morphology, crystalline quality and stress of GaN films have been investigated with different Al x Ga1−x N interlayer thickness, 280nm, 460nm, 575nm, and 750nm. It was found that the properties of GaN films are highly dependent on the Al x Ga1−x N interlayer thickness. High quality crack-free GaN films up to 1.2μm can be achieved with 460nm thick Al x Ga1−x N layer. [ABSTRACT FROM AUTHOR]

Abstract: The main limitation of in-situ γ spectrometry lies in determining the depth distribution of radionuclides. This paper describes a specific delaminated method to obtain depth distribution of 152Eu in soil. It is based on the notion that the relative γ-ray flux contribution from a certain soil layer varies with the depth distribution shape and a certain γ-ray energy. Through one measurement with standard in-situ HPGe γ spectrometry, the activity concentration of 152Eu in any layer at certain soil depth can be iteratively calculated. The unique advantage of the delaminated method for measurement of 152Eu is that neither the priori knowledge of depth distribution shape nor an unwieldy lead collimator is required. Experiments have been performed for feasibility validation at three locations in one radioactive contaminated site. After in-situ measurement at each location, 10 samples from different layers were collected for laboratorial analysis. Experimental results show that the depth distribution of 152Eu is close to Gaussian function shape, and the activity concentration results of the delaminated method are accordant well with the analysis of soil samples, with a maximum deviation of 18.1%. [Copyright &y& Elsevier]

Abstract: A semi-conducting ZnO-based multilayer varistor (MLV) is cofired with a passivation layer with Zn0.9Mg0.1TiO3 (ZMT) composition to prevent ZnO-based MLV from over-nickel coating during nickel plating. The cofiring results show that no de-lamination between ZMT and ZnO can be found, suggesting good co-firing compatibility between ZMT and ZnO though the anisotropic densification of ZMT is noted. However, the microstructure and electrical properties of ZnO based MLV is greatly influenced since ZMT is cofired with ZnO-based MLV. Reduction of grain size of ZnO-based MLV from 5.2 to 3.7μm that is presumably attributed to constraining sintering of ZnO-based MLV by ZMT is observed after cofring ZMT. Simultaneously, the reduction of grain size of ZMT covered ZnO-based MLV results in a decrease of capacitance and in an increase of breakdown voltage. On the other hand, a decrease of non-linear coefficient and an increase of leakage current of ZMT covered ZnO-based MLV are observed as well. The results are associated with the change of slope of I–V curve for ZMT covered ZnO-based MLV due to the formation of a semi-conducting Zn2TiO4 phase, which is resulted from the diffusion of titanium ion into the matrix of ZnO-based MLV during co-firing. [Copyright &y& Elsevier]