DE19924354A1 - Component, e.g. a capacitor, coil or LC filter, comprises a manganese-zinc ferrite-based magneto-dielectric material containing eutectic mixture of lead monoxide and tungsten trioxide - Google Patents

Abstract

A component of Fe2O3, Mn3O4 and ZnO based magneto-dielectric material, containing an eutectic mixture of lead(II) oxide and tungsten(VI) oxide, is new. Preferred Features: The magneto-dielectric material contains 0-1500 ppm of the eutectic mixture.

Description

The invention relates to a component with magneto-dielectric material which contains iron oxide Fe ₂ O ₃ , manganese oxide Mn ₃ O ₄ and zinc oxide ZnO as main components.

Manganese-zinc ferrites are cubic ferrites with a spinel structure, which have the composition AB ₂ O ₄ . A means the octahedral and B the tetrahedral lattice positions in the spinel structure. This spinel structure can be populated in a known manner with a large number of cations of suitable size and oxidation levels. For example, the A sites of one or more of the cations Mn ²⁺ , Zn ²⁺ , Ni ²⁺ , Mg ²⁺ , Co ²⁺ , Fe ²⁺ , the B sites of one or more cations such as Fe ³⁺ and Co ^{3+ can be} substituted.

An important property of these ferrites is their high electrical resistance can be between 0.01 and 1000 Ω.m depending on the composition. Manganese-zinc ferrites have an electrical resistance of approximately 1 Ω.cm. can be further increased by dopants. As a result, the magnetic ver loss of these materials low.

The grain size of the ferrites also influences the amount of magnetic loss. Ferrites with small grain sizes show lower magnetic losses.

Manganese-zinc ferrites are known from EP 0 551 907 A2, which are doped with CaO and SiO ₂ . These doped manganese-zinc ferrites can also contain other oxides. Manganese-zinc ferrites doped in this way show the lowest magnetic losses at frequencies between 1 and 2 MHz. The magnetic losses are significantly higher in lower frequency ranges (a few hundred kilohertz). For example, the magnetic losses of the manganese-zinc ferrites known from EP 0 551 907 A2 are up to 70 times higher at 100 kHz than at 1 MHz.

The object of the present invention is to provide a component with magnetodi to provide electrical material that shows low magnetic losses.

The object is achieved according to the invention by a component with a magnetodielectric material which contains iron oxide Fe ₂ O ₃ , manganese oxide Mn ₃ O ₄ and zinc oxide ZnO as main components, characterized in that the magnetodielectric material is a eutectic mixture of lead (II) oxide and tungsten (VI) oxide is added.

5PbO-WO ₃ shows a eutectic at 730 ° C and improves the sintering conditions by forming a liquid phase. By adding 5PbO-WO ₃ , the sintering temperatures can be kept lower and it is still sufficiently high sintering density. Due to the lower sintering temperatures, smaller grain sizes are achieved, which in turn show lower magnetic loss.

In addition, 5PbO-WO _{3 has} a high electrical resistance of approximately 10 ¹² Ω.m.

It is preferred that the amount of eutek added to the magneto-dielectric material table mixture of lead (II) oxide and tungsten (VI) oxide is between 0 and 1500 ppm.

This added amount of 5PbO-WO ₃ has a particularly positive effect on the amount of magnetic loss.

The magnetodielectric material can be used for electronic components such as accessories play a capacitor, be processed by using electrodes at high Temperatures is sintered. In addition, the magneto-dielectric material in the Manufacture of coils or LC filters can be used.

According to Examples 1 to 3 below, the ferrites were prepared in the following manner provides and then examined for their properties.  

Embodiment 1

A manganese-zinc ferrite, e.g. B. Mn _0.655 Zn _0.254 Fe ²⁺ _0.091 Fe ³⁺ ₂ O ₄ , was prepared from the corresponding molar relations of iron oxide Fe ₂ O ₃ , manganese oxide Mn ₃ O ₄ and zinc oxide ZnO. The oxides were _distilled with H ₂ O. mixed and mixed wet in a steel ball mill. In parallel, a eutectic mixture of WO ₃ and PbO was weighed out and homogenized in a mortar. So much of the mixture of WO ₃ and PbO was then added to the steel ball mill that the content was 500 ppm. The mixture was dried and calcined at a temperature of 850 ° C for three hours. After the calcination, the powder was ground again in a steel ball mill in aqueous suspension for three hours and dried. The powder was then granulated by adding ammonium alginate as a binder, pressing it through a sieve with a mesh size of 1 mm and then processing it into roll granules in a granulating drum. The granules were then pressed into compact molds at a pressure of 50 MPa and dried at 135 ° C. for 24 hours. These molds were sintered in air at different temperatures between 1225 and 1275 ° C for 3 h, then slowly cooled under an equilibrium atmosphere.

Embodiment 2

A manganese-zinc ferrite was produced in the same manner as described in Example 1. So much WO ₃ and PbO were added that the dopant content was 1000 ppm.

Embodiment 3

A manganese-zinc ferrite was produced in the same manner as described in Example 1. So much WO ₃ and PbO were added that the dopant content was 1500 ppm.

Table 1

Sintering densities of the manganese-zinc ferrites at different sintering temperatures and 5PbO-WO ₃ dopant content

Table 2

Magnetic losses of the manganese-zinc ferrites in mW / cm ³ at 100 kHz / 100 mT, different sintering temperatures and different dopant content 5PbO-WO ₃

Table 3

Magnetic losses of the manganese-zinc ferrites in mW / cm ³ at 400 kHz / 50 mT, different sintering temperatures and different dopant content 5PbO-WO ₃

Claims (2)

1. Component with magneto-dielectric material, which contains as main components iron oxide Fe ₂ O ₃ , manganese oxide Mn ₃ O ₄ and zinc oxide ZnO, characterized in that the magneto-dielectric material contains a eutectic mixture of lead (II) oxide and tungsten (VI) oxide. 2. Component with magnetodielectric material according to claim 1, characterized, that the amount of eutectic mixture added to the magneto-dielectric material from lead (II) oxide and tungsten (VI) oxide is between 0 and 1500 ppm.