Influence of processing conditions on dielectric properties of CaCu3Ti 4O12 thin films
CaCu3Ti4O12 possesses one of the largest values of the effecti ve dielectric permittivity in a large frequency and temperature range ever reported for a ce amic material, and is thus a very promising materi l for various electronic and electromechanical applic ations. The origin of such high permittivity has be en attributed to ‘electrical’ heterogeneities in the m icrostructure [1-3]. By Chemical Solution Depositio n, we have prepared CaCu 3Ti4O12 ceramic thin films under different conditions, try ing to establish the influence of microstructure on their dielectric properties.
Separation of grain boundary effects and intrinsic properties in perovskite-like Gd 0.6 Y 0.4 BaCo 2 O 5.5 using high-frequency dielectric spectroscopy
The dielectric response of ${\mathrm{Gd}}_{0.6}{\mathrm{Y}}_{0.4}{\mathrm{BaCo}}_{2}{\mathrm{O}}_{5.5},$ which undergoes a sequence of magnetic and electronic phase transitions, has been investigated in the radio-frequency range from 1 MHz to 1.8 GHz in order to separate the intrinsic properties from grain boundary and sample-electrode interface effects. Analysis of the measured response, showing the characteristics of a damped resonator, reveals the intrinsic dc resistivity, which cannot be detected using the standard four-point measurement method. From the skin-effect-governed dielectric response the temperature dependence of the magnetic permeability was determined.
Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.