DD301288A7 - Ceramic dielectrics of class 2 to IEC (solution 3) - Google Patents

Abstract

The invention relates to dielectrics for capacitors, in particular for multilayer and disk capacitors, and active substances for printed capacitors. In accordance with the invention, ceramic materials of technically pure raw materials based on separately preformed components give Ba in m TiO 3 (Pb ind x Srind 1-x) indn ((Mg in 1/3 Nb in 2/3) ind y Ti ind 1-y) O ind 3 (Pb ind t D ind 1-t) ind p (Ti ind q Zr inds (u ind 1 C ind 1., U ind j C ind j) ind 1-qs) O ind 3 and glass additives based on the oxides PbO, ZnO, B ind 2 O ind 3, SiO 2, Al ind 2 O 3 and Bi ind 2 O ind 3, which are added at least partially fritted, at different sintering temperatures and Curie points the preformed components, taking into account the usable for C and D elements and the in the description of the invention by m, n, p, q, s, t, u, x and y specified proportions by mass and adhering to the stated mass fractions of these four components and preservation of Multiphase in the sintered material suitable dielectrics of class 2 R 1 according to IEC with dielectric constants epsilon ind r> = 2,800.

Description

Field of application of the invention

The invention relates to the field of electrical engineering / electronics and concerns ceramic dielectrics for capacitors, in particular for multilayer and disk capacitors, and active substance sound for printed capacitors.

Characteristic of bekannton prior art, Miniaturization of capacitors and devastation of material economy and labor productivity in manufacturing

These capacitors require an increase in the dielectric constant ε, the effective dielectric while maintaining the lowest possible temperature dependence thereof, z. B. of max. ± 15% in the temperature range from -55 ° C to + 125 ⁰ C for class 2FU according to IEC and X7R according to EIA standard.

This well alu generally known that the increase of the ε, by the use of ferroelectric materials such. B. BaTiO ₃

or mixed crystals, is reached, with increasing ε, increasing dependencies of the same are taken of the temperature mi 'η, and that supplements for lowering the sintering temperature T "in the conventional ceramic

Multilayer condensers are mainly used to reduce the proportion of high-melting expensive precious metals Pd, Pt or Au in the

can lead between the dielectrically, active layers lying electrode layers, the ε, lower.

In compliance with the Tomperaturcharakteristik of the classes 2R1 and a sintering temperature T ₁ below 114O ⁰ C, the solution is after DD-PS 258915 represents a technologically controllable and reproducible solution. With its compositions based on

of BaTiO ₃ and mixtures of bismuth layer compounds and other additives, however, only ε, values are reached around 2000.

Other known solutions, such as DD-PS 140871, DE-OS 2923 981, US-PS 3619220, DE-AS 1640168 and US-PS 3619744

reach the state of the solution according to DD-PS 258915 not by either lower ε, values result and / or the class 2R1 not enough.

Also known is a solution consisting of 2 components of BaTiOs, of which at least 50% of the used Mass fraction must be in the particle size range of 0.7 to 3.0 mm, and a complex Bleiperowskit according to EP 257653. However, the Dielaktrika that meet this solution, which meet the class 2R1, achieve only ε, -values of max. 2920 at Sintering temperatures T "not lower than 1200 ⁰ C. Another solution, according to EP 20o 137, results in compliance with the temperature characteristics of class 2R1 in the best case

ε, values of 3,205. Hereby, a BaTiO ₃ added with Nb ₂ O ₆ or Ta ₂ Oe and Sm ₂ O ₃ or other oxides of the SE elements of the order numbers 57 to 62 and further separately supplied dopants of a mixture of MnO ₂ and NiO used.

Significant disadvantage of this solution, which requires a sintering temperature T of 1230 ° C, and all solutions according to EP 205137 A2

are the high demands on the main component BaTiO ₃ .

The high ε, values are achieved only when using a high-purity, very fine BaTiO ₃ : The solution requires particle sizes

of: £ 1 (in and total impurities of SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ of less than 0.2 mass% in%.) In the conventional large-scale BaTiO ₃ preparation this can only be achieved by using reagent grade, expensive raw materials and more specifically, expensive

Mahlkörper be achieved. Furthermore, these materials are very sensitive to sintering. Even with small deviations from the

optimum sintering temperature, the temperature characteristic of class X7R is no longer complied with. It also occurs

Giant grain growth on which the use in ceramic multilayer capacitors, in which already today sintered effective

dielectric layers with thicknesses from 25pm can be realized excludes.

Object of the invention

The aim of the invention is to find material compositions which, when using industrially produced BaTiO ₃ , enable a reproducible production and complete technical data in the case of ceramic dielectrics of class 2 according to IEC compared with the prior art.

Presentation of the essence of the invention

The invention has for its object to find compositions which, when using BaTiO ₃ with a particle size dso S3,5pm and a purity of 2: 0.98 parts by mass and other at least technically pure raw materials, finally rare earths or mixtures thereof, at sintering temperatures T, i '1200 ⁰ C and a possible sintering interval of r i at least 3OK dielectrics with dielectric constant ε,> 2800 class 2R1 according to IEC result, which are characterized by low die'.elektrische

Losses, high insulation resistance and high withstand voltage and are also suitable for use in ceramic Vielschlchtkoncjensatoren with thicknesses of the sintered, dielectrically effective layers £ 20μηη are suitable. According to the invention, this object is achieved by compositions of three preformed components K1 to K3 and an addition of a low-melting glass G:

K 1 = Ba _n JiO ₃

or Ba _1n TiO ₃ with dopants, where m = 0.97 to 1.00, K 2 - (Pb _x Sr, _, U (Mg ₁ Z ₃ Nb ₂ Z ₃ VTi ₁ _ _Ϋ ) Ο ₃

with x = 0.75 ... 0.98

y = 0.70 ... 0.95

andn = 0.98 ... 1.06,

which has a dielectric constant ε,> 4000 at a sintering temperature between 15O ⁰ C and 125 ⁰ C and at 25 ° C has a dielectric constant ε,> 4000

K 3 = (Pb ₁ D ₁ - OpITIqZr ₁ (U ₁ C ₁ ... UjC ₁ ),. "., 1O ₃

with D & Sr, Ba, Ca, SE or Didym,

C ₁ ... C ₁ & Mg ²⁺ , Ni ²⁺ , Zn ²⁺ , Fe ²⁺ , Co ²⁺ , Mn ²⁺ , Fe ³⁺ , Cb ³ *, Mn ³⁺ , Sc ³⁺ , Ti ^{4 +} , Zr ⁴⁺ , Sn ⁴⁺ , Hf ⁴⁺ , Nb ⁶⁺ Ta ⁶⁺ , Sb ⁶⁺ , W ⁶⁺ , where U ₁ ... uj are the corresponding mole fractions of C, ... C) and W ₁ . ..Wj denote the valences of C ₁ ... Cj, the

j j

which must meet the Molensky conditions for Poroskiteq + s + £ uj = 1 and 4 (q + s) + £ wjUj = 4

1 1

with q = 0.40 ... 0.60

s = 0.30

 and q + s> 0,

t = 0.80.

t = 0.93

 and ρ = 0.98.

.0,55

80

.1,00 for D £ Sr, Ba, Ca or

, 1.00 for D Ä SE or Didym

.1,06,

which at a sintering temperature 115O ⁰ C dense sintered, the dielectric constant ε, at 25 ⁰ C> 2300, has a maximum at> 150 ° C and slowly decreases after negative temperatures, and G is low-melting glass with a hemisphere point to max. 700 ⁰ C, which consists of at least three of the six oxides PbO, B ₂ O ₃ , ZnO, SiO ₂ , Al ₂ O ₃ and Bi ₂ O ₃ .

Both glass fritted glasses and mixtures of these with further of the stated oxides are considered glass additives. The mass fractions of the three preformed and comminuted components K1 to K3 and of the glass additive G in the desired material composition are:

K1 = 0.30 ... 0.67 parts by weight

K2 = 0.10 ... 0.55 parts by mass

K3 = 0.05 ... 0.25 parts by mass and G = 0.01 ... 0.05 parts by mass,

3 3

where I] K = 1.0 and the indication of G as an addition is related to £ K and in the case of a mixture of 1 -1

fritted glass with oxide of oxide content max. 50% of G should be.

Depending on the composition, the density of the mixture formed in a known manner from this mixture at a sintering temperature T, in the range between 112O ⁰ C and 1200 "C.

In compliance with the usual requirements for a capacitor material class 2R1 according to IEC, the dielectric constant ε, at 25 ° C reaches values of at least 2800, with their change in the operating temperature range of -55 ⁰ C to +125 ⁰ C ± 15% does not exceed.

To emphasize here are the low losses tanö.die high and stable insulation resistances Rj, from 1O ¹² ... 10 ¹³ O un ' ¹ high withstand voltage of at least 8kV / mm, which allows the use of very thin layers of the dielectric. Exceeding or undershooting the stated limits for the mass fractions of the three components and the glass offset in the total offset of the material have the following effects:

In the case of component K1, they lead to no longer flat temperature profile of ε ,. In addition, when exceeding the required sintering temperature rises well above 1200 ⁰ C. When exceeding the proportion of component K2 falls the ε ,, which is still high at low temperatures, after higher temperatures too steep; Exceeding the proportion lead at negative temperatures to a ε, -Abfall of more than 15%.

Increasing the proportion of the component K3, the permissible for the class 2Ri maximum ε, drop of 15% at -55 ⁰ C can no longer be met, at the upper limit of the temperature range, at +125 ⁰ C, the allowed ε , Waste not exhausted. Accordingly, if the proportion for K3 falls below + 125 ° C., a strong ε, -fall can occur.

If the limits for the glass content are not reached, the required sintering temperatures T _{1 are increased} , and / or low densities of the ceramic are achieved. If the proportion of glass addition is exceeded, the ε ,, decreases and the desired temperature dependence is not maintained.

ι / ¹ I ι

Adjusting thin foils, such as ζ. For example, for multilayer capacitors, the claimed glass content of undercurrents enables the achievement of a high density, faster shrinkage, small pore space and resistance to impact and the lowest moisture sensitivity of the condensation. The possible formulations counteract the preservation of the totality of the polyvalent material and thus the low ε of the ε, as well as the elimination of special measures for the regulation of the PbO household during sintering.

AusfOhrungsbelsplete The invention is described below with reference to five Ausführungsheispielen in the form of two tables and the statement of the per se

known, in principle identical in all embodiments process steps for the preparation of the individual components K1 to K3, the glass additive G and the Gesamtmaterialstoffes on the basis of the composition according to Embodiment 1 closer.

Table 1 gives the composition and the applied sintering regime, characterized by sintering temperature T ₁ and Holding time, on. Table 2 shows the obtained technical characteristics of the disk-shaped specimens. The starting point of the synthesis is the preparation of the three components and the glass additive. Component KI: BaTiO ₃

The component K1 is formed in a known manner from equal molar proportions BaCO ₃ and TiO ₂ in a two-hour solid state reaction at 120O ⁰ C. Subsequently, fine grinding takes place in drum or vibratory mills. A TiO ₂ excess of up to 0.03 mole fractions is not critical.

Component K2: (Pbo, 88Sro, ij) [(Mg, / ₃ Nb _2/3) o, ₈ Tio, jl0 ₃ First, MgCO ₃ and Nb ₂ O ₆ are preformed by a solid state reaction at 1100 ° C / 3h MgNb ₂ O ₈ . There is one Excess of 0.04 molar amount of Mg in the offset not only uncritical, but even cheap. The preformed MgNb ₂ O ₆ is added according to the proportions by moles of PbO or Pb ₃ O ₄ given by the formula SrCO ₃ and TiO _{2 are} added and this mixture is annealed at 1100 ° C / 2 h. This product is then scaled to a grain size

deo: S 5μηι finely ground. An excess of up to 0.06 molar amounts of PbO or Pb ₃ O _{4 is} permitted.

The sintered at 1175 ° C / 2h component K2 has as a single component an ε,> 5000 at 25 ° C. The ε, maximum, at

is about 50 ° C, has values of> 8000.

The structure is perovskite with low levels of pyrochlore residue. Higher annealing of the component K2 is possible, but not advantageous, since the subsequent comminution thereby

becomes more difficult and the required sintering temperature T _{1 of} the total material increases.

Component K4: Pb [Zr ₀ , ₄ eTio. ₄ e (Nit / ₃ Sb _2/3) o o8] 0 ₃ The preparation is carried out by direct synthesis from the raw materials Pb ₃ O ₄ or PbO, ZrO ₂ , TiO ₂ , NiO and Sb ₂ O ₃ , by adding these

are mixed according to the molar proportions given by the formol and the mixture of a

Solid state reaction at 850 ° C to 900 ⁰ C with 2 h holding time is subjected. This is followed by fine comminution to a grain size of

you: £ 5μπΊ, which in this case was done in a 3 hour treatment in an agate powdered tablet.

The densely sintered at 1280 ° C / 2 h component K3 has as a single component at 25 ⁰ C an ε, of 2 500. The ε, maximum

at about 28O ⁰ C.

Glass additive G:

0.85 mass parts PbO 0.07 mass parts B ₂ O ₃ 0.06 mass parts ZnO 0.01 mass parts Al ₂ O ₃ and 0.01 mass parts SiO ₂

are mixed, the mixture melted in a corundum crucible at 1000 ⁰ C, stirred several times and kept liquid for one hour. Thereafter, the melt is quenched by pouring into cold water, the glass phase is separated from the water, dried, pre-crushed and ground in an agate powder so that the powder has a BET specific surface area of at least 2.5 mVg.

If, as in the exemplary embodiment 5 with B) ₂ O ₃ , there is still an unfired oxide for addition of glass, where the same oxide could already have been part of the frit, then this oxide can either be mixed into the fritted part of the additive G or else be added separately to the offset of the total materials.

To produce the embodiments according to the invention of the total material, the components K1 to K3 produced in the same way or in the same way are mixed with the glass additive G in the proportions given in Table 1 and advantageously annealed again at 1000 to 1050 ° C./1 h and finely ground. This repeated homogenization and fine grinding, which serves for improved homogenization, can also be omitted. In any case, the powdery, inventive material of the product-specific known shape and possibly other required process steps, such as for multilayer capacitors z. B. a metallization ii. a., and then sintered.

Table 1 Composition and mass components of the components

"Jngsbeisp execution.

Component 1 Component 2

Component 3

T. ("C) / hold time (h)

BaTiO ₃

66.3%

25.6%

08.02%

LotglasSystemPbO-ZnO- SiO ₂ -B ₂ O ₃ - Al ₂ O ₃ - + 2.0%

1180/2

A2 BaTiO ₃ 51.0% 30.6% 18.4% ) o.io] 0 ₃ solder glass + 2.0% 1180/2 A3 BaTiO ₃ 40.8% like A 2 35.7% like A 2 23.5% + 1% solder glass + 1% Bi ₂ O ₃ 1180/2 A4 BaTiO ₃ 35.7% (Pb ₀₁₈₈ Sr ₀₁₁₂ ) I (Mg _1n Nb _2n ) O ₁₈ Ti ₀₁₂ ] O ₃ 40.8% 23.5% i.oe] 0 ₃ solder glass + 2% 1180/2 A5 BaTiO ₃ 40.8% like A 2 35.7% like A 2 23.5% + 3% solder glass + 2% Bi ₂ O ₃ 1140/2

table

Ausfühhungsbeisp.

design

1 measuring frequency: 1 kHz.

2 measured at 25 ° C.

3 based on 25 ⁰ C.

tanö »· ²¹ HO" ³ )

insulation resistance

Δε,

in% ³¹

Max. Deviation in the range of

-55 ⁰ C to + 25 ° C

+25 ⁰ C "-t-125 ° C

A1 disc 3100 10 10 " + 5 -12 + 10 -12 A2 disc 3200 11 10 ¹³ + 6 -13 + 10 -10 A3 disc 3000 9 5-10 ¹² + 6 -14 + 10 - 8 A4 disc 3150 10 5-10 " + 7 -14 +11 - 8 A5 disc 2900 12 10 ¹² + 2 -10 + 8 - 8

Claims (4)

1. Class 2 ceramic dielectrics according to IEC on the basis of four different components essentially known in their basic composition, barium titanate, two complex lead pervalskites and added glass, characterized in that at least two different sintering temperatures of the separately preformed components K1 to K3, have at least two different Curie temperatures and that the components are in the range of the following composition: K 1 = Bs _n JiO ₃ with m = 0.97. ..1.00, wherein the barium titanate may also contain up to 3 parts by weight in% of the usual dopants, K 2 = (Pb _x Sr ₁ -X) _n I (Mg ₁ Z ₂ Z ₃ Nb ₃₎ VTi ₁ _ _y] O ₃ with χ = 0.75 ... 0.98 y = 0.70 ... 0.95 and η = 0.88 ... 1.06 K 3 = (Pb ₁ D ₁ _ Op [TJqZr ₈ (U ₁ C ₁ ... U ₁ Cj) ₁ _ _q _ JO ₃ with D £ Sr, Ba, Ca, SE or Didym, C ₁ ... C j δ Mg ²⁺ , Ni ²⁺ , Zn ²⁺ , Fe ²⁺ , Co ²⁺ , Mn ²⁺ , Fe ³⁺ , Co ³⁺ , Mn ³⁺ , Sc ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ , Sn ⁴⁺ , Hf ⁴⁺ , Nb ⁵⁺ , Ta ⁵⁺ , Sb ⁵⁺ , W ⁶⁺ , where q + s + £ uj = 1 and4 (q + s) + £ wjUj = 4, if U ₁ ... Ujdie corresponding molar proportions of C ₁ ... Cjundwi ... Wj denote the respective valences of these C ₁ ... C, -, q = 0.40 ... 0.60 s = 0.30 ... 0.55, where q + s> 0.80 t = 0.80 ... 1.00 for D ^ Sr, Ca, Ba t = 0.93 ... 1.00 for D & SE or Didym
and ρ = 0.98 ... 1.06, G is a low-melting, at least partially fritted glass addition of at least three of the six oxides PbO or Pb ₃ O, ZNO, B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ and Bi ₂ O ₃ with a hemisphere point below 700 ^r C, that they are in mass proportions K1 = 0.30 ... 0.67
K2 = 0.10 ... 0.55
K3 = 0.05 ... 0.25 and
G = 0.01 ... 0.05 are contained in the offset of the respective ceramic dielectric, where Σ K = 1.0 and the proportions of G are related to this sum,
and that the sintered material is multi-phase according to the components. 2. Ceramic dielectrics according to claim 1, characterized in that the component K2 preferably at 25 ° C has a dielectric constant ε,> 4000 and between 115O ⁰ C and 125O ⁰ C dense sintered. 3. Ceramic dielectrics according to claim 1 or 2, characterized in that the component K3 preferably at a sintering temperature> 115O ⁰ C dense sintered, at 25 ⁰ C has a ε _Γ > 2300 and at> 150 ⁰ C has an e _r maximum. 4. Ceramic dielectrics according to claim 1, 2 or 3, characterized in that the glass additive preferably comprises a fritted solder glass made of an oxide batch of 0.85 mass parts PbO
0.07 to 0.06 mass parts B ₂ O ₃
0.04 to 0.06 parts by weight ZnO
0.01 parts by weight of Al ₂ O ₃
0.01 mass parts SiO ₂ and a remainder of max. 0.03 mass fraction of impurities and fluorides. 2. Ceramic dielectrics according to claim 1, 2 or 3, characterized in that the glass additive preferably consists of a trotted solder glass and further of the oxides mentioned under claim 1, in particular of Bi ₂ Oa.