US 6,485,672 B1Granted

Method of manufacturing dielectric ceramic composition and electronic device containing dielectric layer

AssigneeTDK Corporation

InventorsTakeshi Nomura, Shigeki Sato

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Abstract

A method of manufacturing a dielectric ceramic composition comprising at least a main component of BaTiO3, a second subcomponent as represented by (Ba, Ca)xSiO2+x (where, x=0.8 to 1.2), and other subcomponents. The main component and at least part of the subcomponents except the second subcomponent are mixed to prepare a pre-calcination powder and the pre-calcination powder is calcined to prepare a calcined powder. The second subcomponent is at least mixed in the calcined powder to obtain a dielectric ceramic composition having a ratio of each subcomponent to the main component of BaTiO3 of a predetermined molar ratio. It is therefore possible to obtain an electronic device containing a dielectric layer such as a multi-layer ceramic capacitor able to satisfy both of the capacity-temperature characteristics of the X7R characteristic (EIA standard) and the B characteristic (EIAJ standard), even when the dielectric layer is a superthin one of not more than 4 μm and having a small change in the capacity under a DC electric field along with time and further having a long accelerated lifetime of the insulation resistance and a small drop in capacity under a DC bias.

A method of manufacturing a dielectric ceramic composition comprising:

a main component expressed by the formula BamTiO2+n, wherein the “m” in the formula is 0.995≦m≦1.010, “n” is 0.995≦n≦1.010, and the ratio of Ba and Ti is 0.995≦Ba/Ti≦1.010,
a second subcomponent including a sintering aid containing silicon oxide as a main component, and
other subcomponents,
comprising the steps of:
mixing the main component and at least part of the subcomponents except the second subcomponent to prepare a pre-calcination powder,
calcining the pre-calcination powder to prepare a calcined powder, and
mixing at least the second subcomponent in said calcined powder to obtain a dielectric ceramic composition having ratios of the subcomponents to the main component of predetermined molar ratios,
wherein said other subcomponents include at least:
a first subcomponent including at least one type of compound selected from MgO, CaO, BaO, SrO, and Cr2O3,
a third subcomponent including at least one type of compound selected from V2O5 MoO3, and WO2, and
a fourth subcomponent including an oxide of R (where, R is at least one type of element selected from Y, Dy, Tb, Gd, and Ho);
and
at least the second subcomponent is mixed in the calcined powder to obtain a dielectric ceramic composition having ratios of the subcomponents to 100 moles of the main component of:
the first subcomponent:
0.1 to 3 moles,
the second subcomponent:
2 to 12 moles,
the third subcomponent:
0.1 to 3 moles, and
the fourth subcomponent:
0.1 to 10.0 moles (where, the number of moles of the fourth subcomponent is the ratio of R by itself), and
said pre-calcination powder is prepared and calcined so that the molar ratio of the components contained in the pre-calcination powder becomes a (Ba+metal element of the first subcomponent)/(Ti+metal element of the fourth subcomponent) of less than 1 or a (Ba+metal element of the fourth subcomponent)/(Ti+metal element of the first subcomponent) of more than 1.

19 more elements

Abstract

Claims13