Dielectric Ceramic Layers Research Articles

Synthesis and research of polyaluminosilicate chemical structure influence on properties of dielectric layers received by 3D aerosol printing

Polyaluminosilicates with different chemical structures have been synthesized. They have been experimentally studied and a priori estimated. Dielectric ceramic layers have been obtained by means of 3D aerosol printing and studied with the use of synthesized polyaluminosilicates and highly dispersed powder of Al2O3 ceramic filler.

Capacitive biopotential electrode with a ceramic dielectric layer

This paper presents the design of an innovative active capacitive electrode with a ceramic dielectric layer. The electrode meets the requirements for contactless measurement, resistance to motion artefacts and possibility to make long and repeated recordings. The proposed capacitive electrode is distinguished from other capacitive electrodes by the construction of the capacitive coupling element, which is placed on the body surface. While common capacitive electrodes use a metal plate with a relatively large surface area as the capacitive coupling element, the proposed electrode uses a dielectric ceramic layer with high permittivity and a surface area no greater than a few cm2. In order to test the electrode, an electrocardiography (ECG) measuring system was designed. Several different dielectric materials, different sizes of the electrode surface, as well as different electronics of the electrode were compared. The results show 26dB signal to noise ratio (SNR) for the electrode with a ceramic dielectric layer, which was put on a skin over a cotton fabric, compared to 13dB SNR for an electrode with a metal plate with a four times larger surface area.

Correlative Studies on Sintering of Ni/BaTiO3 Multilayers Using X‐ray Computed Nanotomography and FIB‐SEM Nanotomograhy

Synchrotron X‐ray computed nanotomography (nCT) and Focused Ion Beam–Scanning Electron Microscope nanotomography (FIB‐nT) were used to characterize baked‐out and sintered nickel (Ni) electrode–Multilayer Ceramic Capacitors. The three‐dimensional microstructures obtained by two different tomography techniques were quantified and correlated. X‐ray nCT is sufficient to reveal the pore characteristics, whereas the FIB‐nT enables the particles in the initial packings to be identified. In the dielectric ceramic layers, pores preferentially orient horizontally in the layer and the regions near the Ni/BT interface are denser than the inner regions. This anisotropy is possibly caused by compressive stress induced during the heating stage.

Influence of thickness and number of dielectric layers on residual stresses in micromultilayer ceramic capacitors

The residual stresses due to high-temperature processing in micromultilayer ceramic capacitors (MLCCs) with various thicknesses and numbers of dielectric ceramic layers were investigated by using a three-dimensional elastoplastic finite element model with temperature-dependent material properties taken into account. For comparison, an explicit analytical solution for the in-plane residual stress in the dielectric ceramic layer was derived. Both the numerical results and the analytical model showed that the thickness ratio of the dielectric layer to electrode layer has a dominant impact on the residual stress states. There exists a critical thickness for the dielectric ceramic layer in MLCCs in the case of a given thickness of the electrode layer, below which both high tensile out-of-plane stresses and high compressive in-plane stresses could cause the cracking of the brittle dielectric layers near the electrode tips and/or the debonding of the electrode/dielectric interface.

Nickel diffusion in base-metal-electrode MLCCs

Nickel is frequently used as an internal electrode in the advanced base-metal-electrode (BME) multilayer ceramic capacitors (MLCCs). The diffusion of nickel element into the non-reducing perovskite dielectric layers plays an important role in the final quality of MLCCs. In this paper, the diffusion of nickel element from internal electrode to the dielectric ceramic layer was investigated by AES and EPMA experiments. It was shown that during sintering, nickel atoms migrate towards the dielectric layer and an interdiffusion region of hundreds of nanometers in thickness is generated near the internal electrode. The difference in dielectric characteristics between MLCC and disk specimens can be attributed to the existence of the interdiffusion region.

Improved Temperature Dependence of Piezoelectric Element for Pressure Sensor

The temperature dependence of the d33 constant was decreased by connecting a piezoelectric element to a temperature compensating capacitor in series. A bilayered composite piezoelectric element consisting of piezoelectric and dielectric ceramic layers was constructed to reduce the temperature dependence of the d33 constant. The temperature dependence of the d33 constant was thus reduced to less than 3% over the temperature range of -30 to 180° C. Furthermore, the temperature dependent properties of a combustion pressure sensor for an automobile engine based on the composite piezoelectric element developed in this study were discussed.

Improvement of Temperature Dependence of Piezoelectric Elements

The relationships between the equivalent circuit constants of a piezoelectric element and the piezoelectric d33- and g33-constants were first clarified. The temperature dependence of the composed equivalent circuit constants was then decreased by connecting the piezoelectric element to a temperature-compensating capacitor, either in series or in parallel. Furthermore, new sandwich-like piezoelectric elements consisting of stacked piezoelectric ceramic and dielectric ceramic layers were constructed to decrease the dependence on temperature. The piezoelectric d33-constant of Pb(Zr, Ti)O3 changed by about 15% over the temperature range of 0 to 160° C. The new sandwich-like element, however, exhibited a change of less than 3% over the same temperature range.