DE2438910A1 - Strontium-calcium niobate dielectric for microwave applications - having high dielectric constant, low loss and improved temp. stability - Google Patents

Abstract

New dielectric oxide material is based on a cpd. of the formula 2(Sr1-x.Cax)O.yNb2O5 (in which 0.1 = x 1.0 and 0.6 = y 1.5; pref. 0.2 = x =0.6 and 0.6 = y =1.2). It is produced by heating a mixt. of SrCO3, CaCO3 and Nb2O5 at 1000 degrees C for 3 h, moulding and then sintering in air at 1300-15550 degrees C for 2-22 hr. For microwave applications, e.g. in miniaturised integrated microwave circuits to stabilise the frequency of the oscillator, as dielectric resonators etc. The material has high dielectric constant, low loss factor and lower temp. coefft. (down to below 40 ppm/degrees C) than conventional dielectric materials.

Description

Oxide dielectric material and method of making it The invention relates to a dielectric oxide material and especially to such compounds, which are suitable as microwave dielectric material, which have a high dielectric constant, a low dissipation factor and a dielectric constant with an improved Has temperature stability.

The invention further relates to a method for producing a such oxide material.

In microwave technology, dielectric materials are used for resistance adjustment used by microwave circuits and serve as dielectric resonators and the like. When the technology of integrated microwave circuits was recently developed, was the miniaturization intensively studied, with dielectric materials applied that have a high dielectric constant and a low dissipation factor possessed to stabilize the frequencies of the oscillator.

Dielectric materials used for the aforementioned purposes so far were used many times, included BaO-TiO2 compounds, as well as corresponding Compounds in which smaller proportions are replaced by other elements, as well TiO2 compounds with a dielectric constant with negative temperature coefficients in combination with a dielectric compound that has a positive temperature coefficient owns. These conventional materials have hitherto been remarkable Difficulties as some of them high dielectric loss factors and some have large deviations in the temperature coefficient of the dielectric constant.

The object of the invention is therefore to provide an oxide dielectric material indicate that has a high dielectric constant and a low dielectric constant Loss factor with a smaller temperature coefficient than the conventional one dielectric materials. The dielectric oxide material is intended as a microwave material be particularly suitable.

The object is achieved according to the invention in that the dielectric Oxide material consisting essentially of a compound with the general formula 2 (Sr1-x . Ca) 0. y Nb205, where x is a number in the range 0.1 # x o1.0 and y is a number in the range of 0.6 # y <1.5.

The object is also achieved according to the invention in that the oxide dielectric material consists essentially of a compound with the general Formula 2 (Sr1 x cax) 0. y Nb205 where x is a number in the Range of 0.2 # x # 0.6 and y is a number in the range of 0.6 # y s 1.2.

Particular features and advantages of the invention are set out below clarified by means of an attached table.

The method of making the invention consists of the following Steps: Starting materials are Sr003, CaC 0 3 and Nb205. These materials are weighed according to the desired oxide compound of the product and then mixed intensively in a ball mill. The mixture will be at about 100,000 for about 3 hours long preheated and pressed into a mold.

The mold is made in the presence of air at a temperature of 13000 sintered to 15500C for 2 to 22 hours.

The dielectric constant E and tan # of the dielectric material (dielectric loss factor) of the sintered product are determined by the perturbation method measured using a TE105 type resonator. The frequency used for measurements was used was 9 GHz. The results of the measurements are in the table summarized at the end of the description.

The dielectric constants were determined for each compound at -30 ° C, -10 ° C, 0 ° C, 25 ° C, 50 ° C and 80 ° C were measured and the temperature coefficients were determined according to the following equation: ## 1 # # 106 ppm / ° C # 1 #t where # 1 is the dielectric constant at 25 ° C, ## denotes the difference between # 1 and the dielectric constant is at t ° C and at means the temperature difference between 250C and t00. That kind of calculated maximum and minimum temperature coefficients are in the column of the Table "Temperature coefficients of s" compiled. The connection, for which only one value is listed in the specified column, such as the connection with No. 2 has no maximum and minimum values for a temperature coefficient von E. In other words, such compounds have a value with a constant Temperature coefficient.

As the table shows, such compounds are according to the invention preferred dielectric materials that have a relatively high dielectric constant <, a low dielectric pleasure factor tan6 and also a small one Have temperature coefficient of dielectric constant.

The material of the invention has been shown to be a microwave dielectric material used, which has a high dielectric constant and a low temperature coefficient the dielectric constant in the microwave range.

It was also found that the dielectric of the present invention Material has a low dielectric loss factor and a high temperature coefficient the dielectric constant also in the low frequency range and has excellent Exhibits results when used in ceramic resonators.

When a dielectric material has a dielectric constant has a temperature coefficient of over + 300 ppm / ° C, then it is called dielectric Material not very suitable in a microwave dielectric resonator.

Furthermore, there have hitherto been difficulties in matching the resistance of the microwave circuits. A dielectric material in which the x-value in the above general formula according to claim 1 assumes the value zero or 1 is of the invention excluded because ee is a temperature coefficient of the dielectric constant Beyond the above limit, as the table shows. links where the y value in the general formula according to claim 1 is the same 1.5 also has a temperature coefficient beyond the above limits and is therefore not an option either.

When y is 0.6, the temperature coefficient is dielectric constant in such a compound as a function of the x-value outside or within the range of + 300 ppm / ° C. The compounds of the invention dielectric material are therefore essentially limited to the area in where the x-value is positive and less than 1.0 but not less than 0.1 and the y value is equal to or greater than 0.6 and less than 1.5, with the general Formula 2 # (Sr1-x # Cax) O.y Nb205 applies.

When the connection of the dielectric material according to the invention the range 0.2 <x # 0.6 and 0.6 c y 9 1.2 is limited, will be excellent Microwave dielectric materials are obtained that have a very good dielectric constant with temperature stability, i.e. a dielectric constant with a Temperature coefficients of less than 40 ppm / ° C can be achieved.

Tabel Connection sintering sintering properties temperature No. ratio temperature time at 25 ° C coefficient xy ° C (hours) # tan # x10-4 from # (ppm / ° C) 1 0 1.0 1470 4 23.47 8.1 -150 # -310 2 0.1 °, 5 1400 3 27.00 50.0 -480 3 0.1 0.6 1400 3 20.00 8.1 -400 4 0.1 0.7 1400 3 22.53 8.8 - 50 5 o, 1 1.0 1470 2 23.00 5.5 - 50 # + 15 6 0.1 1.4 1400 3 25.48 6.2 + 70 7 0.1 1.5 1400 3 27.60 7.6 +400 8 0.2 1.0 1450 2 22.45 3.0 - 16 # +32 9 0.2 0.6 1500 2 37.00 0.8 -16.7--20 10 0.3 0.6 1550 10 36.00 1.5 - 92 11 0.3 1.0 1420 10 37.15 6.5 - 10 # + 15 12 0.3 1.2 1380 4 40.05 3.5 + 82 13 0.35 0.8 1390 20 38.00 1.1 - 25 # -30 14 0.35 1.0 1410 10 42.60 4.1 - 7 # + 9 15 0.35 1.1 1380 10 40.95 5.1 - 1 # # + 13 16 0.4 0.6 1550 10 52.15 0.5 -220 17 0.4 0.7 1400 3 42.66 4.6 -180 18 0.4 0.8 1400 3 43.00 5.3 - 30 19 0.4 0.8 1380 10 44.10 2.5 - 18 # -28 20 0.4 0.9 1360 10 43.80 3.5 - 6 # + 10 21 0.4 1.0 1360 10 42.94 3.5 -2.5 ~ +10 22 0.4 1.0 1430 2 43.14 4.1 - 2 +13 23 0.4 1.1 1320 5 44.30 2.8 + 6 # +18 24 0.4 1.2 1300 20 4 +, 60 4.4 + 25 # +36 25 0.4 1.2 1400 3 43.82 4.5 - 40 26 0.4 1.4 1400 3 45.73 6.6 +150 27 0.4 1.5 1400 3 48.10 6.2 +320 28 0.45 0.9 1380 10 44.20 1.5 -3.1 # +6.4 29 0.45 1.0 1360 10 42.32 2.1 -1.5 # +7 30 0.45 1.0 1340 22 42.60 4.1 -0.5 # +4.3 31 0.45 1.1 1380 10 42.50 3.5 -0.5 # +8.1 32 0.5 0.9 1380 10 42.1C 1.8 -5.1 # +11 Connection sintering sintering properties temperature No. ratio temperature time at 250C coefficient xy ° C (hours) # tan # x10-4 from # (ppm / ° C) 33 0.5 1.0 1360 10 40.60 2.4 +1.0 # +16 34 0.5 1.1 1380 10 41.20 3.6 + 11 # +29 35 0.5 1.2 1380 4 42.31 4.3 + 33 36 0.6 1.0 1360 10 39.70 4.5 + 37 37 0.6 1.0 1400 3 39.70 7.1 + 60 38 0.8 1.0 1400 3 35.15 8.2 +105 39 0.9 0.6 1400 3 30.39 9.0 - 36 40 0.9 0.7 1400 3 32.74 11.0 - 50 41 0.9 1.0 1400 3 35.10 9.3 +120 42 0.9 1.4 1400 3 40.67 8.0 +200 43 0.9 1.5 1400 3 44.70 8.0 +600 44 1.0 1.0 1400 3 34.47 8.7 + 315 + 580 Claims

Claims (3)

Claims 3 dielectric oxide material, characterized in that that it essentially consists of a compound with the general formula 2 (Sr1-x # Cax) 0 #y Nb2O5, where x is a number in the range 0.1 # x C1, and y is a number in the range of 0, @ # y <1.5. 2. Dielectric @@ material, characterized in that it is essentially consists of a compound with the general formula 2 (Sr1-x # Cax) 0 # y Nb2O5, where x is a number in the range 0.2 # x # 0.6 and y is a number in the range of 0.6 'y # 1.2. 3. Method for producing the dielectric oxide material according to Claim 1 or 2, characterized in that the starting materials SrCO3, CaCO3 and Nb2O5 du @ hmixed and heated to about 100,000 for about 3 hours and put into a mold are pressed and that the form is then in the presence of l @@ t bti a temperature from 1300 to 1550 ° C during 2 to 22 is sintered.