JPH0244608A - Dielectric porcelain - Google Patents

Abstract

PURPOSE:To thin the thickness of a dielectric by adding specific amounts of specified components to BaTiO3 powder which was synthesized and heat-treated in advance so as to bake them. CONSTITUTION:To 100 moleportion of BaTiO3 powder which was synthesized and heat-treated in advance, Nb2O5 by 1.8-3.85 mole % in terms of NbO5/2, and MnO2 by 0.4-1.0 mole % are added, and further one kind or two or more kinds of compounds selected from a group of compounds consisting of ZrO2, BaZrO3, SrZrO3 and CaZrO3 are added by not less than 0.1wt.% and not more than 2.0wt% and there are baked. Hereby a dielectric porcelain which can be used even for the thickness of 20mum or less, that is, which can be used even for the thickness of 50V/mm or less, that is, that tan delta is 2.5% or less even at the magnetic field strength of 50V/mm and further which has the CR product (the product of capacitance and insulation resistance) of 1000OMEGA.F or more can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention conforms to the Y class B characteristics of the JIS standard (rate of change in dielectric constant within ±10% from 125 to 85°C) and the EIA standard (El
electronic industries assoc
Suitable for high dielectric constant dielectric ceramics that meet the X7R characteristics (change rate of dielectric constant within ±15% at -155 to 125°C) of the Standard), especially for multilayer ceramic capacitors used with thin dielectric layers of 20 μm or less. The present invention relates to dielectric porcelain.

Conventional technology BaTiO3-based porcelain has been used as a high-permittivity ceramic capacitor material, but pure a
Since TiOs cannot be used as a capacitor due to large temperature changes in dielectric constant and large losses, various solid solution formations and additives have been proposed.

The material that satisfies the Y class B characteristics of the JIS standard and the X7R characteristics of the EIA standard in the BaTi0a system is pure aTi.
Since the temperature characteristics are obtained by a composite of a composition having a Curie temperature of Os and a composition having a Curie point at or below room temperature, BaTi used as a starting material
The particle size, crystallinity, impurities, etc. of Os have a large effect on the temperature characteristics after firing. An example of such a material is BaTi
Porcelain made by adding B i 203 to O3 is used. In recent years, with the miniaturization of electronic components, multilayer capacitors have become important components.

This capacitor consists of sheet-molded dielectric material and electrodes alternately.
These are laminated and fired at the same time. If the electrode and dielectric material react during firing, a capacitor cannot be formed, so the combination of electrode material and dielectric material is important. Dielectrics containing B i 203 cannot be used in multilayer capacitors because they react with commonly used Pd electrodes. B for multilayer capacitors
Material made by adding Nb20a and CO20s to aTiOs
(Japanese Unexamined Patent Publication No. 61-275164, etc.) is used, and the dielectric constant is 3000 to 4000. Also, Ba
As a material in which Nb2O5 and MnO2 are added to TiOs, the material described in JP-A-51-76597 is known.

Problems to be Solved by the Invention There is a demand for smaller multilayer capacitors with larger capacity, but for this purpose it is necessary to form a thin dielectric layer using a material with a high dielectric constant.

In addition, in general, in a ferroelectric material such as BaTiOs, the applied electric field strength is large (and the loss (tan δ) becomes large.The thickness of the conventionally used dielectric layer is about 30 μm, but the thickness of 20 μm or less is Since the characteristics of a capacitor are evaluated by the signal voltage of I V r m s , if the dielectric layer is thin (if conventional materials are used, the tan δ specified by the standard is It exceeds the value of 2.5% and becomes unusable.BaTi
A material made by adding Nb2O5 and CO2O3 to Os has a high dielectric constant, but tan δ increases rapidly with an increase in signal voltage (1 kHz), so if the thickness is less than 20 μm, it does not meet the standards. B as a dielectric porcelain that can be used even with a thickness of
We propose a material in which N b 205 and MnO2 are added to aTiOs. tan δ at high field strength is M
n It becomes smaller as the amount of O2 increases, but the insulation resistance value decreases, making it undesirable as a capacitor.

The present invention solves these problems and can be used even with a thickness of 20 μm or less, that is, tan δ is 2.5% or less even at an electric field strength of 50 V/mm, and 100 μm or less.
It is an object of the present invention to provide a dielectric ceramic having a CR product (product of capacitance and insulation resistance) of 0 or more.

Means for solving the problem A specific amount of Nb2O5 and MnO2 was added to BaTiOs powder synthesized and heat-treated in advance, and a specific amount of Z was added.
rO2, BaZr0a, SrZrO3, and CaZrOs are added and fired.

By adding specific amounts of Nb2O5 and MnO2 to working BaTiO3, low tan δ can be obtained with high electric field strength, and furthermore, specific amounts of ZrO2, BaZrOs, S r Z
By adding rO3 and CaZrO3, the insulation resistance increases.

Examples B synthesized by solid-phase reaction method, hydrothermal method, or barium titanyl oxalate method and heat-treated at 1000 to 1250°C
NbO2/6, M in the amount shown in Table 1 for aTiOs
Additives containing nO2 and ZrO2 were weighed and mixed with pure water for 15 hours using a ball mill containing zirconia balls in a polyethylene container. After mixing, the slurry was granulated by adding an aqueous PVA solution to the dried powder. Put the granulated powder into the mold and make 500 kg/c! diameter 1 at a pressure of
3 old, molded into a disc shape with a thickness of 1w@. 700 molded bodies
After incinerating the binder by heating at ℃ for 1 hour, 1250 ~
The optimum firing temperature is shown in Table 1 by firing at 1450° C. for 2 hours and the temperature at which the density is maximum. Cr--Au was vacuum-deposited on both sides of the disk of the obtained fired body to form electrodes, and a sample for measurement was prepared. The temperature characteristics of the dielectric constant are 1kHz, l
Vrms, measured in a temperature range of -60 to 150°C. In addition, in order to investigate dielectric properties at high signal field strength, a 1 kHz signal was heated at 150 Vrws, /mu at room temperature.
The dielectric constant and tan δ were measured by applying up to
．． The voltage (V2.S) at which the voltage becomes 5% was determined. Capacitance-resistance product (
CR product) was determined from the resistance value and capacitance measured with a high insulation resistance meter.

Table 2 shows the dielectric constant at room temperature, tan δ, ■2.5, CR
Each temperature (-55, -2
5, 85, and 125°C).

Table 1 Samples marked with a zero are reference examples outside the scope of the claims Table 2 Samples marked with the year are tables of reference examples outside the scope of the claims 1 (Continued) Samples marked with a book are reference examples outside the scope of the claims Samples marked with this year are reference examples Tables 1 and 2 outside the scope of claims.
Among the examples shown in , Nos. 1 to 3 are BaC03 and TiO2 calcined at 1150°C using a solid phase reaction method.
TiOs is used as a starting material, and Nos. 4 to 18 use hydrothermally synthesized BaTiO3, and Nos. 19 to 30 use BaTiOs obtained by thermally decomposing barium titanyl oxalate, and each uses a powder heat-treated at 1050° C. as a starting material.

As is clear from Tables 1 and 2, in additive-free porcelain, C
Although the a product is 1000 Ω・F or less, ZrO2, BaZ
In porcelain containing 0.1 wt% or more of rO3, SrZrO3, CaZrO3, and CaTi03, the Ca product is improved,
The value is 1000Ω・F or more. However, 2.0
Porcelain added in excess of wt% has a lower dielectric constant and an increased rate of temperature change, which does not meet the JIS and EIA standards mentioned above, and is therefore excluded from the scope of claims.

Effects of the Invention Since the dielectric ceramic of the present invention has small loss even at high signal voltages, it is possible to reduce the thickness of the dielectric material to 10 μm or less, which was conventionally required to be 20 μm or more, and
Since it has a high Ca product of 000Ω·F or more, it is preferable as a ceramic for multilayer ceramic capacitors.

Claims (1)

[Claims] BaTiO_3 powder 100 synthesized in advance and heat treated
Based on the molar part, Nb_2O_5 is converted to NbO_5_/_2 and is 1.8 to 3.85 mol%, and MnO_2 is 0.4
~1.0 mol% added, and further ZrO_2, BaZrO
_3, SrZrO_3, CaZrO_3, one or more compounds selected from the group consisting of 0.1
Dielectric porcelain fired with addition of wt% or more and 2.0wt% or less.