X7R Dielectrics Research Articles

Effect of re-oxidation on dielectric properties in Ni-MLCC

The effect of re-oxidation treatment on the solubility of dopants and the dielectric properties of rare-earths (La, Ho) and V-substituted BaTiO3 solid solutions, assuming the shell phase of X7R dielectrics, was investigated. Ho-V-substituted samples showed larger increase of the lattice parameter and Tc by re-oxidation treatment compared with La-V-substituted samples. Electron spin resonance measurements revealed that the oxidation of V3+ to V4+ or V5+ appeared in the range in which the increase of lattice parameter by re-oxidation treatment was observed. This suggests that the increase of Tc is due to the change of preferential occupational site of Ho ion from A-site to B-site, being accompanied with the oxidation of V3+. We also investigated the effect of re-oxidation treatment on the electrical properties and microstructure in Ni-MLCC samples, using rare-earths (La, Ho, Yb) and acceptors (Mn, V) doped BaTiO3 based X7R dielectrics. The change in temperature characteristic of the dielectric constant by re-oxidation treatment was observed for the MLCC samples containing V with smaller content. In the case of Ho-V- and Yb-V-doped samples showed larger increase of the dielectric constant at around 120 °C compared with La-V-doped samples. The relationship between the microstructure and electrical properties of the MLCC sample was investigated by impedance measurement at elevated temperature.

X7R용 적층 칩 세라믹 캐패시터 조성의 희토류 첨가에 따른 유전 특성

Effects of E<TEX>$_2$</TEX>O<TEX>$_3$</TEX>. HO<TEX>$_2$</TEX>O<TEX>$_3$</TEX> and Dy<TEX>$_2$</TEX>O<TEX>$_3$</TEX> addition on dielectric properties of non-reducible BaTiO<TEX>$_3$</TEX> based X7R dielectrics with Ni electrode have been studied in a reduced atmosphere. As the content of rare-earth with E<TEX>$_2$</TEX>O<TEX>$_3$</TEX>. HO<TEX>$_2$</TEX>O<TEX>$_3$</TEX>, Dy<TEX>$_2$</TEX>O<TEX>$_3$</TEX> was less than 3wt%, The TCC(Temperature Capacitance Change) and insulation resistance characteristics were improved by compensate the oxygen vacancies due to occupy either the Ba or Ti site. We developed the composition of X7R (EIA standard) for higher capacitance MLCC which had high reliability electric properties by the addition of Er ion into BaTiO<TEX>$_3$</TEX> + MgO + Y2O<TEX>$_3$</TEX> + MnO + (Ba<TEX>$\sub$</TEX>0.4/Ca<TEX>$\sub$</TEX>0.6/)SiO<TEX>$_3$</TEX> composition.

Copper Cofire X7R Dielectrics and Multilayer Capacitors Based on Zinc Borate Fluxed Barium Titanate Ceramic

Copper cofired dielectrics may give new opportunities for high temperature capacitors. To demonstrate feasibility, BaTiO3 has been formulated into X7R dielectrics with copper inner electrodes. This requires the development of a formulation that permits sintering at temperatures below 1000°C, and then firing in a reducing environment in atmospheres pO2 ∼ 10−8 atms. ZnO—B2O3 chemistries were explored with additional dopants to modify densification and the temperature coefficient of capacitance of the BaTiO3 dielectric anomaly. X7R characteristics with relative dielectric permittivities ∼2750 and tanδ ∼ 0.01 at 1 kHz were obtained at room temperature. Multilayer capacitors were fabricated in 3.2 mm × 1.6 mm size multilayers with an acrylic binder system and oxidation resistive copper inner electrodes.

Influence of Ce doping on structure and properties of BaTiO3based X7R dielectrics

The effects of Ce doping on the lattice parameters, permittivity, and sintering characteristics of the BaTiO3-Nb2O5-Co2O3-Sm2O3-Li2CO3 system were studied. It was found that addition of CeO2 could improve dielectric properties at low or medium sintering temperatures. The structure, permittivity, and density of sintered ceramics were influenced by the vacancies introduced by donors and acceptors. Defect behaviour is also discussed.

Effects of Rare-Earth Oxides on the Reliability of X7R Dielectrics

The effects of rare-earth oxides, e.g., La, Nd, Sm, Dy and Yb, on the reliability of multilayer capacitors (MLCs) with X7R dielectrics and Ni electrodes were investigated. Microstructures of the dielectrics were analyzed by transmission electron microscopy (TEM) and electron probe microanalysis (EPMA) in order to characterize the rare-earth ions. Incorporation of rare-earth ions to BaTiO3 ceramics depended on their ionic radius, resulting in different microstructures and electric performances of dielectrics. Dy ions provided BaTiO3 ceramics with ideal X7R characteristics and high reliability. The mechanism governing leakage current was discussed in terms of the voltage dependence of leakage current. Electric properties and related reliability of the capacitors were attributed to solubility, distribution of rare-earth oxides and their occupation site in BaTiO3.

Mechanical behavior of ceramic capacitors

Fracture toughness, modulus of rupture (MOR), and thermal shock resistance were evaluated on COG, X7R, and Z5U type commercial ceramic capacitors with and without internal electrodes. Fracture toughness measurements show similar values for X7R and Z5U dielectrics and a slightly higher value for COG dielectrics. The presence of electrodes slightly increases the strength of all the dielectrics. MOR measurements indicate that the COG samples are relatively stronger, followed by X7R and Z5U dielectrics. Weibull modulus values are higher for X7R dielectrics followed by COG and Z5U dielectrics. These results show that the critical temperature difference for fracture initiation is close to 75 degrees C for 5819 size samples and close to 125 degrees C for 1206 size Z5U and 150 degrees C for X7R and COG dielectrics.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>