Kinetics of Oxygen Diffusion into Multilayer Ceramic Capacitors During the Re‐oxidation Process and its Implications on Dielectric Properties

Abstract

The re‐oxidation process is an important thermal processing step to minimize oxygen vacancies and to produce a high resistivity and more reliable multilayer ceramic capacitors (MLCC) upon co‐firing with Ni internal electrodes. A model X7R capacitor based on Ho2O3 amphoteric doping is investigated in prototyped multilayer devices. The dielectrics are co‐fired in a standard low pO2 sintering process. The re‐oxidation thermal process of these multilayer devices is then investigated with a series of “in‐situ” impedance measurements. These measurements are performed in a temperature range from 400° to 500°C in air. The relative impedance change is used to determine effective chemical diffusion coefficients and associated activation energy. The electrical conductivity is analyzed to determine properties, such as Schottky barrier height and degradation lifetime, under different re‐oxidation conditions. Furthermore, transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) are applied to consider the microstructure, microchemistry, and oxygen stoichiometry changes.

Analysis of the degradation of BaTiO3 resistivity due to hydrogen ion incorporation: Impedance spectroscopy and diffusion analysis

“…This modeling approach makes sense, since the amount of hydrogen in the active layer affects the amount of measured resistivity in impedance spectroscopy tests, and the closest way for hydrogen ions to enter the active layer is through the exposed surface. This experimental set up is similar to that used by Donnelly and Randall for calculating oxygen diffusion in BaTiO 3 and lead oxide volatility in PZT piezoceramics [13,22,29].…”

“…Those techniques can be as simple as exposing samples to hydrogen and watching the color change from the exposed surface toward the virgin area [12] or using more advanced techniques, such as impedance spectroscopy [10,13], thermal desorption studies (TDS) [14], quasi-elastic neutron scattering (QENS) [15], or proton nuclear magnetic resonance (NMR) [5]. The reported diffusion coefficient for the same material can be different in different papers.…”

Synergistic effect of rare-earth elements on the dielectric properties and reliability of BaTiO 3 -based ceramics for multilayer ceramic capacitors

“…The presence of the low frequency arc in the complex impedance spectra indicates an ionic space charge polarization [35,36]. Such a response occurs due to the particular charged defects, in this case oxygen vacancies, being blocked at the electrodes, whereas the electronic conduction is reversible [36][37][38].…”

“…[37][38][39] in the inset illustration. The model is composed of an electronic rail which corresponds to the grain and grain boundary impedance in the high frequency region, and an ionic rail that includes a Warburg impedance (W s ) in the low frequency region.…”

Effect of Mg on the dielectric and electrical properties of BaTiO3-based ceramics

“…It has been determined that the doping of trivalent rare-earth ions and manganese ions is effective in improving the reliability of BaTiO 3 dielectrics [5][6][7]. Hence, the addition of a donor or an acceptor and the re-oxidation processes became the effective means of preventing the degradation of insulation resistance and to extend the service life of MLCCs [4,8]. Among these processes, the incorporation of Mg acceptors into BaTiO 3 has the effect of fixing the positively charged oxygen vacancies through ionic compensation.…”