Wen-His Lee

Effect of Inner Electrode on Electrical Properties of (Zn,Mg)TiO3-Based Multilayer Ceramic Capacitor

In this study, different proportions of silver–palladium alloy used as an inner electrode are adopted to fabricate (Zn,Mg)TiO3-based multilayer ceramic capacitors. Effects of sintering temperature, and measuring frequency on the dielectric properties of the samples with different proportions of the Pd–Ag inner electrode are investigated. The continuity of the inner electrode and the proportion of Pd–Ag of the inner electrode of samples sintered at different temperatures play important roles in determining the dielectric properties.

Characterization of ZnO-Based Multilayer Varistor Sintered by Hot-Press Sintering

To attain the homogeneous microstructure of ZnO-based multilayer varistors (MLVs), hot-press sintering is conducted. To determine the effect of hot-press sintering on the microstructure, the dielectric and varistor properties of ZnO-based MLVs were investigated and compared with those of ZnO-based MLVs fabricated by free sintering. In hot-press sintering, the average grain size and the distribution of grain size of a ZnO-based MLVs are both reduced. The results show that the leakage current and nonlinear coefficient ( α) of ZnO-based MLVs can be improved. The increase in nonlinear coefficient ( α) is directly related to the inhibition of grain growth of ZnO grains when hot-press sintering is performed instead of free sintering. Note that the energy absorption capabilities in terms of peak current (PC) measurements of ZnO-based MLVs are remarkably improved due to the homogeneity of microstructure when hot-press sintering is conducted.

Effect of Inner Electrode on Reliability of (Zn,Mg)TiO3-Based Multilayer Ceramic Capacitor

In this study, different proportions of silver-palladium alloy acting as the inner electrode were adopted to a (Zn,Mg)TiO3-based multilayer ceramic capacitor (MLCC) sintered at 925 °C for 2 h to evaluate the effect of the inner electrode on reliability. The main results show that the lifetime is inversely proportional to Ag content in the Pd/Ag inner electrode. Ag+1 diffusion into the (Zn,Mg)TiO3-based MLCC during cofiring at 925 °C for 2 h and Ag+1 migration at 140 °C against 200 V are both responsible for the short lifetime of the (Zn,Mg)TiO3-based MLCC, particularly the latter factor. A (Zn,Mg)TiO3-based MLCC with high Ag content in the inner electrode Ag/Pd=99/01 exhibits the shortest lifetime (13 h), and the effect of Ag+1 migration is markedly enhanced when the activation energy of the (Zn,Mg)TiO3 dielectric is greatly lowered due to the excessive formation of oxygen vacancies and the semiconducting Zn2TiO4 phase when Ag+ substitutes for Zn+2 during co-firing.

Mn-Doped BaO–(Nd0.7,Sm0.3)2O3–4TiO2 Ceramic Sintered in a Reducing Atmosphere

The effect of MnCO3 doping from 0 to 55 mol % into BaO–(Nd0.7Sm0.3)2O3–4TiO2 (BNST) sintered in a reducing atmosphere on the phase transformation, microstructure and electrical properties was studied. The variation of d-spacing with Mn content can be divided into three regimes in this study. In regime (I), 0 to 5 mol % Mn-doped BNST, the d-spacing decreases successively until 5 mol % which is the maximum solubility, because Mn+3 is incorporated into Ti+4-sites of BNST. In regime (II), 5 to 42 mol % Mn-doped BNST, the d-spacing remains constant and Mn2O3 is precipitated because the amount of MnCO3 doped is more than the solubility. In regime (III), 43 to 55 mol % Mn-doped BNST, the d-spacing is the same as BNST without MnCO3 doping. Heavily doping MnCO3 into BNST gives rise to two parallel reactions, forming two ternary systems, BaO–(Nd,Sm)2O3–TiO2 and BaO–(Nd,Sm)2O3–Mn2O3. Mn-doped BNST sintered in a reducing atmosphere is in a semiconducing state in regimes (I) and (II), because the concentration of free electron is higher than that of the acceptors. In contrast, Mn-doped BNST in regime (III) sintered in a reducing atmosphere is in an insulating state because the concentration of the acceptors is higher than that of liberated free electron.