Ca-acceptors in dielectric ceramics sintered in reducive atmospheres

This paper investigated resistivity and dielectric properties of magnesium doped BaTiO 3 . Influence of variable doping concentration and Ba/Ti ratio on densification, microstructure, resistivity and dielectric properties was studied. Ceramics sintered in pure nitrogen had higher apparent density than that of ceramics sintered in air. Second phase occurred when Mg doping concentration was greater than 2 mol%. Ceramics sintered in pure nitrogen had higher resistivity than ceramics sintered in air when A/ B ratio ≥1. When Ba/Ti ratio was equal to 1.01, resistivity of the samples sintered in pure nitrogen increased with doping concentration increasing. Dielectric constant changed little with doping concentration increasing, but leakage conductivity decreased much. Samples with Ba/Ti ratio of 1.005 had the largest dielectric constant irrespective of doping concentration.

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Studies of resistivity and dielectric properties of magnesium doped barium titanate sintered in pure nitrogen

Yao

Zhang

2007

“…[11]. Incorporation of Ba 2+ on the A-sites can make the primary A-sites Ca 2+ shift to B-sites which greatly changes the unit cell volume and Curie temperature [12,13]. In our investigation, the experiment was divided into to two series called A and B, respectively.…”

Section: Introductionmentioning

confidence: 99%

The study of Ca-doped BCTZ ceramics sintered in reducing atmosphere

Chen

Wang

et al. 2007

Effects of Ca 2+ doped into (Ba 1−x Ca x )(Ti 1−y Zr y )O 3 (BCTZ) ceramics on microstructure and insulation resistance have been investigated. It is found that the shift of Ca 2+ from A-sites to B-sites greatly influences the unit cell volume and the Curie temperature of BCTZ ceramics. During the firing process in reducing atmosphere, the large amounts of additive Ca 2+ dispense among the grain boundaries and lead to the restrain of the grain growth. Within the same volume, the specimen with smaller grain size provides more grain boundaries, which helps in providing an efficient diffusion pathway for oxygen during annealing step and results in the improvement of the insulation resistance of the samples.

“…Oxygen vacancies left behind in the dielectrics by this firing atmosphere lower the insulation resistance of the devices and degrade their reliability [3,4,[9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Microstructural Analysis of X7R-Type BaTiO3 Multilayer Ceramic Capacitors (MLCCs)

Feng

McConville

2005

The microstructures of typical commercial X7R MLCCs were characterized by transmission electron microscopy (TEM), using tripod polished specimens and ion milled samples. Core-shell structures were clearly observed in the TEM specimens, and glass phases located at the grain boundaries and triple points were frequently observed. Their chemical composition was analyzed using energy dispersive X-ray spectrometry (EDS), which showed bismuth ions diffused into the shell regions, while the cores were pure BaTiO 3 . X-ray diffraction (XRD) suggested that the predominant phase in the microstructure had pseudocubic global symmetry, while ferroelectric domains were observed in TEM bright field (BF) images. The internal electrodes in the devices were an alloy of Ag/Pd, and these regions were found to have twinned crystal structures. The stress states in the interfaces between the electrodes and the dielectric layers were revealed, and no silver migration in the flux at the electrode-dielectric interfaces was observed.