NANO complex oxide doped dielectric ceramic material, preparation method thereof and multilayer ceramic capacitors made from the same

Abstract

The present invention provides a nano complex oxide doped dielectric ceramic material used for a multilayer ceramic capacitor using a base metal as a material of internal electrodes. The doped dielectric ceramic material comprises barium titanate and a nano complex oxide dopant, wherein the molar ratio of the barium titanate to the nano complex oxide dopant is in the range of (90˜98):(2˜10), the average particle size of the barium titanate is 50˜300 nm and the nano complex oxide dopant has the following formula (1): w A+x B+y C+z D. The present invention also provides processes for preparing the nano complex oxide doped dielectric ceramic material and ultrafine-grained and temperature-stable multilayer ceramic capacitors using the nano complex oxide doped dielectric ceramic material as the material of dielectric layers.

Description

TECHNICAL FIELD OF THE INVENTION[0001]The present invention relates to a dielectric ceramic material. Particularly, the present invention relates to a nano complex oxide doped dielectric ceramic material used for an ultrafine grained and temperature-stable multilayer ceramic capacitors employing a base metal such as nickel as the material of internal electrodes.TECHNICAL BACKGROUND[0002]With rapid development of various types of electronic devices, there is a tendency that these devices and products are smaller in size and larger in capacitance. The component parts for these devices are also increasingly produced in compact and lightweight design. The means for mounting the electronic components are also changing to surface mounting technology (SMT). Small components such as capacitor and resistor are called “chip components”.[0003]Multilayer Ceramic Capacitor (MLCC) is a widely used typical chip component. It is generally fabricated by forming alternating layers of an internal elec...

AI Technical Summary

Benefits of technology

[0031]The nano complex oxide doped dielectric ceramic material is mixed with suitable organic solvent, binder, dispersant and plasticizer to provide a ceramic slurry; a dielectric layer is formed by a tape-casting method using the slurry with the thickness of the dielectric layer of below 10 μm; multiple of the dielectric layers and base-metal internal electrode layers are alternately stacked to prepare a stack body; the binder is removed after the stacked body is formed; the binder-removed stack body is then sintered under a reducing atmosphere at a temperature of from 950° C. to 1250° C.; the stack body is then reoxidized in a weak oxidation atmosphere at 800° C.˜1100° C. to enhance insulation resistance of the dielectric; and then the stack body is cooled down to room temperature and Cu or Ag terminal electrode is mounted to obtain an ultrafine-grained and temperature-stable multilayer ceramic capacitor having base-metal internal electrodes.

Problems solved by technology

However, use of such noble metals becomes a barrier to cut down the production cost of multilayer ceramic capacitors.

However, if such base metals are used as a material for internal electrodes and fired in the conventional firing conditions of the dielectric ceramic materials, they would be oxidized easily and lose functions as the internal electrodes.

However, this dielectric ceramic composition is of no practical use since its insulation resistance and temperature coefficient of capacitor are affected by the grain size of the main component BaTiO3, thus making it difficult to control the composition to obtain stable dielectric properties.

However, the sintering temperature for this system is too high, over 1300° C. and the TCC at −55° C. or 125° C. is near −15%.

Thus, the composition is not suitable for industrial production.

However, the reducing of the grain size generally induces the decreasing of the dielectric constant.

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