DE2634145C3 - Ceramic dielectric - Google Patents

Description

The invention relates to a ceramic dielectric which has a high dielectric constant and a high quality Q , is stable in the temperature characteristics and is intended for decimator devices (microwave devices). those at frequencies of 300 MII /. work up to 30 GHz.

Recently, attempts have been made to find decimeter wave (microwave) circuits in the field the high frequency circuits designed to operate at decimeter wave and millimeter frequencies with wavelengths of no more than a few decimeters are intended to be miniaturized.

These high frequency circuits use cavity resonators and antennas. These However, the usual components must correspond in their sizes to the decimeter wavelengths, so that the Use of such components is an obstacle to miniaturization of the circuits. To switch off this disadvantage has been proposed to use ceramic dielectrics instead of conventional metallic materials use. Many of the commonly used ceramic materials consist essentially of masses of the Titanate systems, e.g. B.

Components addressed as main components TiO ₂ and La ₂ O ₃ contain at least one additive

the group consisting of CaO, SnO ₂ and ZrO ₂ may or may not be present. For example contains

ί the ceramic dielectric insulating material according to DE-PS 7 67 364 U ₂ Oj and TiO ₂ as main components, with tin oxide as secondary components

and / or zirconium oxide are included.

In practice, dielectrics, the lanthanum oxide

in and titanium dioxide as essential main components not contained in the frequency range used as it is indicated in the present application, what from the following experimental Data can be seen:

ι ^r i compositions of the system

La ₂ O ₃ -TiO ₂ -SnO ₂ -ZrO ₂

with the proportions of the components disclosed in DE-PS 7 67 364 have the following electrical properties (I. shafts: The dielectrics were produced in the manner described in DE-PS 7 67 364.

CaTiO ₃ -MgTiOj-La ₂ O ₃ · 2TiO ₂
MgTiOj-CaTiO ,.

However, with these masses it is impossible to produce dielectric components with sufficient properties for required for use in microwave ovens. Dielectric materials must low dielectric loss, high dielectric constant and have a low temperature coefficient of dielectric constant, however none of the above-mentioned materials have sufficient properties as those mentioned above Meet the requirements at the same time.

DE-PS 7 67 316. 7 67 364 and 7 67 426 describe the use of lanthanum oxide, titanium oxide and zinc oxide as electrical insulating materials, in particular as ceramic dielectrics for capacitors. They have a high dielectric constant and an At I MHz

At 4 GHz

r. 35-38
Q: 8000
7T: ± 10 X ΙΟ " ⁶ / C

ε: 35-38
Q: under 2000
TC: ± 10 x 10 "'/

constant, so that such insulating means are suitable to increase the capacitance of the capacitor. None of these patents describes compositions of five components as defined according to the invention, but they are mainly based on compositions with two or three or four components Have frequencies of 1 MHz, but a considerably reduced low Q at ultra-high frequencies of 4 GHz

Γ · have. Therefore, these dielectrics, which are called The main components do not contain lanthanum oxide and titanium dioxide and, as additives, tin oxide and zirconium oxide for high frequencies from 300MHz to 30GHz working microwave equipment such. B. dielectric Resonators in microwave band pass filters, antennas used for these frequencies or substrates for microwave circuits can be used.

The invention relates to a for high frequencies

αί certain ceramic dielectric with high dielectric constant, high quality C (ie low dielectric loss) and low temperature coefficient of the resonance frequency. The ceramic dielectric intended for high frequencies according to FIG

V) The invention makes it possible to produce dielectric ceramic components whose temperature coefficient of the resonance frequency can be adjusted as desired by changing the quantitative ratio of the components.

π object of the invention is therefore a ceramic dielectric for high frequencies consisting essentially of a basic composition consisting of 22-43 wt .-% titanium dioxide, 38 to 58 wt .-% zirconium oxide, and 9 to 26 wt .-% tin (lV ) oxide and one

bo additive consisting of lanthanum oxide and zinc oxide and present in an amount of at least 0.5% by weight of the total amount of base and additive is, wherein the lanthanum oxide in an amount of up to 2 wt .-% and the zinc oxide in an amount up to

b5 7 wt .-% of the total amount of base and Additive are present.

The above-mentioned limitation of the proportion of the constituents is necessary for the following reasons:

If the amount of titanium dioxide is less than 22% by weight, the dielectric constant of the products becomes low, while on the other hand, amounts exceeding 43% by weight cause a large increase in the temperature coefficient of the resonance frequency. If the zirconia is less than 38% by weight or more than 58% by weight, the temperature coefficient of the resonance frequency becomes too high. If the proportion of tin (IV) oxide is less than 9% by weight, the Q becomes low, while if the amount exceeds 26% by weight, the temperature coefficient of the resonance frequency increases.

If the additives are present in amounts less than 0.5% by weight, the sintering of the product is insufficient, thereby deteriorating the dielectric constant and the Q factor, while on the other hand an amount larger than 10% deteriorates the Q factor causes. If the lanthanum oxide is present in an amount of more than 2% by weight, the Q deterioration results, while the ZnO amount in excess of 7 % by weight deteriorates the dielectric constant and the Q factor. .

The ceramic dielectrics according to the invention can be prepared according to methods conventionally used for production applied by ceramic dielectrics. A preferred method in which high purity oxides are used will be described below.

The high-purity oxides TiO ₂ , ZrO ₂ , SnO ₂ , La ₂ Oj and ZnO are used as starting materials for the production of the ceramic dielectrics of the examples listed in Tables 1 and 2. In each experiment, the mixture of the powdery starting materials in the proportions given in Table 1 was ground for 16 hours in a ball mill with water. The resulting mixture was dehydrated, dried and pressed under a pressure of 2500 kg / cm ² into a disc having a diameter of 12 mm and a thickness of 5.5 mm. The disk was sintered for 4 hours at 1320 ^° C. in a natural atmosphere and thereby converted into a ceramic body.

The electrical properties were measured for each ceramic body. The results are in the table 1 called. The following properties are given

Table 1

ben: dielectric constant, Q and temperature coefficient the resonance frequency at a microwave frequency of 7GH /. at 25 ° C. In the tables are with marked with an asterisk (*) products that do not fall within the scope of the invention.

The dielectric constant and the Q factor at microwave frequency were measured according to the known dielectric resonance method. The temperature coefficient of the resonance frequency TQfo) represents

ίο the rate of change of the resonance frequency (fo) over a temperature range of + 25 ° C to + 85 ° C. The rate of change of the resonance frequency as a function of the temperature was derived from the temperature coefficient of the dielectric constant TC (ε) and the thermal expansion coefficient λ of the ceramic body. The relationship between the temperature coefficient of the resonance frequency TC (fo) and the temperature coefficient of the dielectric constant 7 "C (e) is given by the following equation:

TCiJo) = - « TCi,) - τ

The results in Table 1 show that according to the invention it is possible to produce ceramic dielectrics having a high dielectric constant and a high Q at microwave frequencies. In addition, the ceramic dielectrics according to the invention

JO low temperature coefficient of the resonance frequency. In addition, according to the invention, it is possible by changing the proportions of the components ceramic dielectrics with any temperature coefficient of the resonance frequency in the range of

J5 -16 10-VC to +56 χ 10-VC so that dielectric ceramic components from the ceramic masses with a heat compensation function for the others electrical components in the high-frequency circuits in which the ceramic components are contained are, can be produced. The ceramic dielectrics according to the invention are thus suitable for the production of dielectric resonance circuits in 'microwave filter sieve chains or as antennas for Microwave frequencies can be used, or as

Base plates for microwave circuits.

example Basic mass ZrO ₂ SnO ₂ Additive La ₂ O ₃ e Q TC Wt% 56 24 Weight% 0.5 TiO ₂ 52 26th ZnO 0.5 (χ ίο " ⁶ / C) I * 20th 58 20th 1.0 0.5 33.8 6500 -9 2 22nd 52 24 1.0 0.5 33.9 6400 -12 3 22nd 56 20th 1.0 0.5 33.9 6700 +43 4th 24 48 24 1.0 0.5 34.2 7300 -9 5 24 52 to 1.0 υ, j 34.4 6500 0 6th 28 56 16 1.0 0.5 34.7 6800 -11 7th 28 44 24 1 Λ
I, U 0.5 IC ^ Τ \ Πί \ _c 8th 28 48 20th 1.0 0.5 35.7 5900 +21 9 32 52 16 1.0 0.5 35.6 7400 -16 IO 32 56 12th 1.0 0.5 35.7 7500 -4 11th 32 1.0 36.5 5800 + 1 12th 32 1.0 37.5 6400 +20

₁ Λ fi ^u continuation Basic mass 5 SnO ₂ 26 34 145 La ₂ Oj ε 6th Q TC I ί -L ·. J example Wt% 9 0.5 Vi TiO ₂ 26th 0.5 (X 10 '* / C) t H Γ 33 20th Additive 0.5 38.8 4800 +38 ί ί 13th 36 ZrO ₂ 16 Wt% 0.5 36.7 6900 +4 U [
H 14th 36 58 12th ZnO 0.5 37.2 7700 -7 15th 36 38 24 1.0 0.5 37.9 6800 -1 ! 16 36 44 20th I ₁ O 0.5 38.8 5500 + 12 \ 17th 40 48 16 1.0 0.5 43.3 6900 +79 ι I _1_ C 18 * 40 52 12th 1.0 0.5 40.6 6700 +21 TlIJ 1 I. 19th 40 36 1.0 0.5 39.9 6600 +4 * 1 20th 40 40 9 1.0 0.5 40.2 5700 +7 ■ J.
J. 21 43 44 12th 1.0 0.5 44.2 6400 +55 I. 22nd 43 48 26th 1.0 0.2 43.1 5700 +25 23 46 38 26th ι, ο 1 46.5 5600 +75 24 * 22nd 48 26th ι, ο 3 34.3 6800 25th 22nd 42 26th 1.0 0.5 34.3 5000 26th 22nd 52 26th 1.0 2 34.2 500 +4 ± 5 27 * 22nd 52 26th 0.5 0.2 33.9 6400 28 22nd 52 26th 0.5 3 33.0 5000 29 22nd 52 26th 0.5 2 31.9 4900 30th 22nd 52 116 1 0.2 31.9 300 31 * 22nd 52 116 3 3 30.7 500 32 * 32 52 116 7th 0.5 36.7 6200 +7 ± 5 33 32 52 116 7th 1 36.6 200 34 * 32 52 116 :O 1 36.5 5800 35 32 52 116 0.5 2 36.4 4900 36 32 52 116 0.5 3 35.6 5500 37 32 52 116 1 0.2 35.5 4300 38 32 52 116 1 3 35.5 300 39 * 32 52 116 3 2 34.3 4200 40 32 52 26th 3 0.5 34.2 200 41 * 32 52 26th 3 2 33.1 300 42 * 36 52 26th 7th 3 36.7 6900 43 36 52 26th 7th 2 36.9 4900 44 36 38 26th 10 0.5 36.8 300 45 * 36 38 26th 0.5 3 36.7 4500 46 36 38 19th 0.5 0.2 34.8 4500 47 36 38 19th 0.5 3 34.6 200 48 * 43 38 19th 1 0.5 40.5 6100 49 43 38 19th 7th 1 40.4 500 50 * 43 38 19th 7th 2 40.2 5700 51 43 38 19th 0.5 3 39.3 5400 52 43 38 19th 0.5 1 39.2 4800 53 43 38 1 38.1 200 54 * 43 38 3 36.8 1900 55 * 38 3 38 7th 10

Claims (1)

Claim: Ceramic dielectric for high frequencies, consisting essentially of a ground wire. those from 22 to 43 wt .-% titanium dioxide. 38 to 58% by weight of zirconium oxide and 9 to 26% by weight Tin (IV) oxide and an additive consisting of lanthanum oxide and zinc oxide and in one An amount of at least 0.5% by weight of the total amount of base and additive is present. the lanthanum oxide in an amount of up to 2% by weight and the zinc oxide in an amount of up to 7 % By weight of the total amount of base composition and additive are present.