The Effect of Rare Earth (Ln = Gd, Dy, Y and Yb) Doping on the Microstructure and Reliability in BaTiO₃-Based Monolithic Ceramic Capacitors (MLCs)

Abstract

The effect of rare earth (Ln = Gd, Dy, Y and Yb) and Mg ions on the microstructure and reliability of BaTiO3-based monolithic ceramic capacitors (MLCs) with Ni electrodes was investigated. The X-ray diffraction results about the lattice volume of sintered specimens suggested that Gd and Dy ions predominatly substituted into the Ba-site, Yb ions gave exclusive substitution at the Ti-site, while Y ions occupied either the Ba- and Ti-site. The reliability of ceramic capacitors was increasing with increasing the ionic radius of the rare earths in this study. The nonlinearity coefficient() etsimated from the leakage currents and the lifetime measured from the highly accelerated lifetime testing (HALT) showed a negative correlation which was observed only from Dy and Y ions doped specimens. The quantity of Ln and Mg in the grains tended to increase with increasing the Ln ionic radius. In order to improve the reliability and the insulation property of BaTiO3 based MLCs with Ni electrodes, it is important that acceptor ions at the Ti-site compensate donor ions which are rare earth ions at the Ba-site, so the overall quantity of the dopants required for the charge compensation with acceptor and donor ions increases accordingly.

Structure fluctuation in Gd- and Mg-substituted BaTiO3with cubic structure

“…[1][2][3][4][5][6][7] The Gd-and Mg-substituted barium titanate crystals (Ba 1−x Gd x )(Ti 1−x=2 Mg x=2 )O 3 were found as one of the suitable materials from the viewpoint of the dielectric properties and stability of ceramics. 8) Structure fluctuations of BaTiO 3 in the paraelectric cubic phase, especially the fluctuation of Ti ions, have also been discussed extensively in connection with the successive phase transition mechanism of BaTiO 3 . X-ray diffuse scattering, single crystal structure analyses, NMR measurements, X-ray laser speckle, and other studies suggested symmetry breaking above the ferroelectric phase transition temperature T C = 403 K. [9][10][11][12][13][14] A recent convergent-beam electron diffraction study successfully gave a direct evidence of the 〈111〉 offcentered Ti ion.…”

Off-centering of rare-earth ion in (Ba,R)(Ti,Mg)O3 (R = Gd, Dy)

“…[1][2][3][4][5][6][7] When the trivalent R and divalent Mg ions are substituted simultaneously for the Ba and Ti ions, respectively, solid solutions of the chemical formula (Ba 1−x R x )(Ti 1−x=2 Mg x=2 )O 3 are formed from the viewpoint of charge compensation. This atomic co-substitution improves the dielectric properties and stability of BaTiO 3 ceramics, 8) and at the same time reduces the ferroelectric phase transition temperature T C of BaTiO 3 with increasing Gd and Mg contents. The phase transition temperature of perovskite-type ABO 3 ferroelectrics including B metal ions with d 0 electronic configurations has often been discussed in connection with the B d-O 2p orbital hybridization.…”

Structural Characteristics of (Ba0.94Gd0.06)(Ti0.97Mg0.03)O3in Cubic Structure Determined by High-Energy Synchrotron-Radiation Powder Diffraction

“…We have recently revealed that Gd is the most effective rare-earth element R for suppressing insulation degradation for applied voltage and temperature stress among (Ba 0:94 R 0:06 )(Ti 0:97 Mg 0:03 )O 3 -based MLCCs. 7) High permittivity (>10000) at room temperature and high specific resistance (>10 10 Ám) can be achieved up to 400 K in (Ba 0:94 Gd 0:06 )(Ti 0:97 Mg 0:03 )O 3 .…”