No description available.

A study was conducted into the intrinsic degradation behavior of X7R and Z5U capacitors. The major goals of this research were: 1) to determine current-voltage, activation energy and leakage current characteristics for such capacitors. 2) to investigate how these characteristics change with degradation; 3) to investigate possible correlations between observed behavior and capacitor microstructure or composition. Examination of capacitor microstructures revealed large differences in grain morphology and electrode spacings. The development of a color gradient between positive and negative electrodes with. degradation was observed in one type of capacitor. Compositional studies using EDAX, AUGER, and microprobe analyses failed to detect gradients in dielectric composition in degraded capacitors indicating that gradients are less than 0.1 atomic percent. Current-voltage studies showed a 3/2 power dependance, at voltages above one volt for X7R capacitors indicating space charge limited current. This dependance was attributed to point emission from electrode protuberances. The 3/2 dependance was observed to shift to a square law behavior with degradation. This change was attributed to a increase in conductivity of the dielectric near the cathode, blunting the effect of electrode protuberances. Z5U capacitors were found to have ohmic behavior. No Schottky or Poole Frenkel currents were observed. Degradation studies were carried out on capacitors at 2 to 8 times the rated voltage, and at temperatures from 100 to 1500℃. Leakage currents in actively degrading capacitors were observed to rise exponentially with time. This rise was accompanied by a gradual decrease in activation energy. A model is proposed to explain the observed current vs degradation behavior. / Master of Science

Thesis (M.S.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 12, 2009) Vita. Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 65-67). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 65-67). Also available on the Internet.

The major objectives of this study were to examine electrical conduction properties of BaTiO3-based multilayer ceramic ( MLC ) capacitors in order to gain a better understanding of the conduction transport mechanisms inside the devices. The experiments involved mainly leakage current versus time measurements under both low temperature-low voltage stress and high temperature-high voltage stress. It was established that leakage current conduction in a MLC capacitor under temperature-voltage stress can be divided into three different conduction regions due to different mechanisms. Those regions are polarization current, DC conduction current and degradation current. The polarization current decreases with time as a power law relation, i.e. Ic(t) t-m where the exponent value m is strongly dependent on the type of capacitor and temperature, but is only weakly dependent on the applied voltage. It has been proposed that two degradation models ( a charge carrier concentration model and a reduction of grain boundary barrier height model ) can explain the degradation behavior for the Z5U devices tested. Degradation measurements indicate that the lifetime for Z5U capacitors can be described by Minford's expression. However, these models account only partly for X7R degradation. X7R behavior, is characterized by an early power law time dependence, followed by exponential voltage dependence. The most probable conduction transport mechanism in X7R capacitors is small polaron hopping, while grain boundary transmission may be the predominant conduction transport mechanism in Z5U capacitors. / Master of Science

The electrical characteristics, including degradation, of high K (≅ 500) barium titanate based thick film capacitors were studied. It was found that a gold conductor made from Au metallo-organic paste is not compatible with the porous high K dielectric material. The leakage current of a thick film capacitor made from Ag/Pd thick film conducting paste and high K dielectric has shown ohmic and space charge limited current behavior with a 3/2 power voltage dependence. Voltage independence of thermal activation energy and time dependence of a leakage current have been observed. A healing effect by reversal of bias polarity and humidity effect on leakage current have also been studied. The 3/2 power voltage dependence can be attributed to point emission from surface indentations or clusters of Ag particles at the electrode. Two possible degradation mechanisms based either on simple vacancy movement or a reduced grain boundary potential barrier height are suggested. It has been found that an electronic conduction model based on reduced grain boundary barrier height is more reasonable than that of simple vacancy induced current model. / M.S.

Pure, single phase stoichiometric Pb(Fe_0.5Nb_0.5)O₃ (PFN) powders were successfully formed by molten salt synthesis using mixture of NaCl and KCI salts. Lower temperatures and shorter times (0.5 hour at 800°C) were needed for single phase PFN formation from molten salts relative to those required for solid-state methods (4 hours at 1000°C). A systematic study indicating the effects of process parameters, such as temperature, time, and amount of flux with respect to starting oxides, on the PFN formation mechanism and its resulting powder characteristics is reported. The particle size increased with increasing synthesis temperature, the rate of increase is greatest above 900°C which is close to the melting point of lead oxide. PFN powders formed by molten salt synthesis were cuboidal, and were free from agglomerates. The sinterability, microstructure, and dielectric properties of these powders have been studied for the pure form and with the presence of lead oxide or lithium carbonate. The dielectric properties were sensitive to as-sintered density, the type of additive and the amount of additive. For pure PFN, the highest valve of dielectric constant is 12,270 at 1MHz, which is sintered at 1100°C for 13 hours. Ceramics sintered with lead oxide additive exhibited inferior dielectric properties although lead oxide served as a sintering aid to increase the as-sintered density. The dielectric properties of PFN with lithium carbonate sintered at 1000°C were attractive: the dielectric constant was increased to 14,000 at 1MHz and the D.C. conductivity was reduced. This reduction in the D.C. conductivity was interpreted in terms of the substitution of lithium for iron. / Master of Science

The objectives of this research are to accomplish Multilayer Ceramic Capacitors, MLCCs used Temperature compensated type Ceramic powder and different design and size to confer its characteristic. The first to speak about Taiwan capacitors property development to point Multilayer Ceramic Capacitors from 1960 to recently.The manufacture procedure from Normal Metal Electronic procedure change to Base Metal Electronic procedure. The second to quote the relation document to explain Temperature compensated type Multilayer Ceramic Capacitors characteristics and main electric characteristics and the related factors such as Frequency, Test Signal Level, DC Bias, Temperature, Time, Insulation resistance and Break down voltage. The last from sample manufacture flow and structure analysis to electric characteristic measure analysis and result to discuss opposite factor characteristics. To bring up develop direction and reference material.

The mechanical and electrical properties of thin films have been become important and urgent in recent years, especially, the laminated structure made by films stacked over hundreds of layers. For example, the Multi-Layered Ceramic Capacitors (MLCCs) are such structures fabricated by one layer ceramic film interleaves with one layer electrode film repeatedly a hundred times. Thus, the advantages of MLCCs include small volume, mass product, and high capacity. That makes the MLCCs the necessary part of passive components. The Finite element method is adopted in the study. The model is built by the simulation program of ANSYS. After meshing and setting boundary conditions, the numerical process is performed. The numerical simulation was started first by applying a uniformly distributed pressure on the top of near hundred layers of MLCCs before sintering process with the bottom plate fixed. Then, the displacement and stress fields of MLCCs under five pressures were obtained and discussed. In order to visualize the results, the data of displacement and the stress fields were listed in Tables and plot in Figures. In addition to the MLCCs under vertically and uniformly distributed pressure, the slightly slant distributed pressure and gradient distributed pressure had been simulated. Next, the results of changing Young¡¦s modulus had also been received. It is found that the vertical distributed pressure and slant distributed pressure were not the main factor led to the side deformation. The lateral constraint of gradient distributed pressure would influence the deformation of the MLCCs significantly.