A rare earth oxide-based microwave dielectric ceramic with both chemical and temperature stability and a preparation method thereof

Abstract

The present invention belongs to the technical field of preparation of electronic information functional materials, and discloses a rare earth oxide-based microwave dielectric ceramic with both chemical and temperature stability and a preparation method thereof. The chemical formula is (1-x)Sm2O3–xMgO; wherein, x is the mass fraction and 0.10 ≤ x ≤ 0.25; using samarium trioxide and magnesium oxide as raw materials, the samarium oxide-based microwave dielectric ceramic is obtained by the traditional solid-state sintering method, and no aging and decomposition phenomenon is seen when exposed to air, and the dielectric constant ε r is 20.0 to 16.2, the quality factor Q×f is 49,700 to 63,600 GHz, and the resonant frequency temperature coefficient τ f is +15.3 to -6.3 ppm / °C. By adding magnesium oxide, the present invention inhibits the aging and decomposition of the samarium oxide ceramic; by adjusting the addition amount of magnesium oxide, near-zero adjustment of the resonant frequency temperature coefficient τ f is achieved while ensuring a high quality factor Q×f value.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of electronic information functional materials, and relates to a microwave dielectric ceramic material capable of stably existing in air and having a near-zero temperature coefficient of resonant frequency by adjusting the content of a second phase, and a preparation method thereof. Background Art

[0002] Microwave dielectric ceramics refer to ceramics used as dielectric materials in microwave (300 MHz - 300 GHz) frequency band circuits to perform one or more functions, and are key basic materials in modern communication technologies. They are widely used in microwave components such as dielectric resonators, filters, dielectric substrates, dielectric waveguide circuits, microwave capacitors, duplexers, antennas, etc. There are mainly three factors for evaluating the performance of microwave dielectric ceramics: dielectric constant (ε r ), quality factor (Q×f), and temperature coefficient of resonant frequency (τ f ). The working environment of the device is not constant, so the stability of performance becomes crucial. The temperature stability of the resonant frequency of microwave dielectric ceramics is an important index, and generally requires τ f to be near zero (|τ f |~0), which is related to whether the device can maintain working stability in a temperature change scenario. In the aerospace field, good temperature stability has even become the primary requirement for material applications.

[0003] As an important strategic resource, rare earths have attracted more and more attention, making more work focus on the research of their properties. For example, rare earth ions can be used as the luminescence centers of phosphors; rare earth oxides can be used as modifiers for glass or ceramics; cubic rare earth oxides can be directly sintered into transparent ceramics. However, the research on the microwave dielectric properties of rare earth oxide ceramics is relatively less. The article "The microwave dielectric properties of xTiO 2 —(1-x)CeO 2 ceramics" in Materials Letters in 2002 reported the microwave dielectric properties of CeO 2 -(1-x)CeO 2 as: ε 2 = 24, Q×f = 57,000 GHz, τ r = -104 ppm / °C. The article "Sintering parameters and Nd doping on Y f O 2 O 3Effects of sintering parameters and Nd doping on the microwave dielectric properties of Y 2 O 3 Y 2 O 3 The microwave dielectric properties of ceramics are: ε r =10.76, Q×f=82,188GHz, τ f =-54.4ppm / ℃. The 2023 article "Ionic Polarizability and Crystal Structure Effects on the Relative τ f and high Q RE 2 O 3 Effects of ionic polarizability and crystal structure on microwave dielectric properties of RE 2 O 3 (RE=La,Eu)ceramics with oppositeτ f and high Q) reported by La 2 O 3 and Eu 2 O 3 The microwave dielectric properties are: ε r =18.6, Q×f=71,400GHz, τ f =-35.1ppm / ℃ and ε r =17.9, Q×f=35,000GHz, τ f = +19.6ppm / ℃. At the same time, La 2 O 3 and Eu 2 O 3 Ceramics all undergo aging and decomposition, but the combination of the two inhibits the decomposition. 2 and Y 2 O 3 Due to the difference in chemical properties, it can exist stably in the air. It can be seen that the reported rare earth oxide ceramics have good microwave dielectric properties, but generally have a large |τ f |, which is not conducive to practical applications.

[0004] For samarium oxide (Sm 2 O 3 )’s microwave dielectric properties, the only report is the 2004 article “(1-x)CeO 2 –xCaTiO 3 and (1-x)CeO 2 –xSm 2 O 3 Microwave dielectric properties of (1-x)CeO 2 –xCaTiO 3 and(1-x)CeO 2 –xSm 2 O 3 ceramics), the microwave dielectric properties reported in the article are: ε r =24, Q×f=46,000GHz, τ f = +22ppm / ℃. Finally, the near-zero τ f In 0.1CeO 2 –0.9Sm 2 O 3 Obtained in (τ f =-5ppm / ℃). In this report, the authors 2 O 3 Adding 0.5wt% CuO to the system inhibits the aging decomposition of the ceramic.

[0005] In summary, by 2 O 3 It is of practical significance to compound it with other materials to ensure its chemical stability and improve its microwave dielectric properties, especially temperature stability. Summary of the invention

[0006] The present invention is directed to Sm 2 O 3 The technical problem of poor chemical stability and temperature stability of microwave dielectric ceramics provides a Sm 2 O 3 High chemical stability, low loss, τ f Adjustable ceramic composite material and preparation method thereof. By adjusting the content of the second phase of alkaline earth metal oxide, the near-zero adjustment of the temperature coefficient of the resonant frequency is achieved while ensuring a high Q×f value, while also having chemical stability. Compared with other rare earth oxide-based microwave dielectric ceramics, the Sm 2 O 3Ceramic-based composite materials have the obvious advantages of low loss and good temperature stability.

[0007] The present invention is achieved through the following technical solutions:

[0008] According to one aspect of the present invention, a rare earth oxide-based microwave dielectric ceramic material having both chemical and temperature stability is provided, wherein the system chemical expression is (1-x)Sm 2 O 3 –xMgO; where x is the mass fraction and 0.10≤x≤0.25.

[0009] Furthermore, it is obtained by using samarium trioxide and magnesium oxide as raw materials through a traditional solid-state sintering method.

[0010] Furthermore, the composite ceramic has good chemical stability and no aging or decomposition phenomenon is observed.

[0011] Furthermore, the dielectric constant ε r is 20.0~16.2, the quality factor Q×f is 49,700~63,600GHz, and the resonant frequency temperature coefficient τ f +15.3~-6.3ppm / ℃.

[0012] Preferably, x=0.20.

[0013] According to another aspect of the present invention, a method for preparing the rare earth oxide-based microwave dielectric ceramic material having both chemical and temperature stability is provided, and the method is carried out according to the following steps:

[0014] Step 1: Mixing ingredients; pre-burning samarium trioxide and magnesium oxide raw material powder to remove moisture; according to the chemical formula (1-x) Sm 2 O 3 –xMgO, x is the mass fraction and 0.10≤x≤0.25. Weigh samarium trioxide and magnesium oxide raw materials and mix them to form a mixture;

[0015] Step 2: ball milling: using zirconium dioxide balls as the ball milling medium and anhydrous ethanol as the dispersion medium, the raw materials, anhydrous ethanol and grinding balls are placed in a nylon tank and ball milled on a planetary ball mill to obtain a uniformly mixed slurry;

[0016] Step 3: drying and sieving: drying the slurry obtained in step 2 and sieving to obtain dry powder;

[0017] Step 4: granulation and tableting; adding 5 wt% polyvinyl alcohol solution to the dry powder obtained in step 3 for granulation, and preliminarily pressing the granulated powder into a green billet using a manual tablet press, and then further pressing it in a cold isostatic press;

[0018] Step 5: Debind the green compact obtained in Step 4 at 500°C to 600°C for 1.5 to 2.5 hours;

[0019] Step 6: Sinter the green compact after debinding in Step 5 within the range of 1400°C to 1600°C, with a holding time of 4 to 6 hours, to produce (1-x)Sm 2 O 3 –xMgO microwave dielectric ceramics, where x is the mass fraction and 0.10 ≤ x ≤ 0.25.

[0020] Furthermore, in Step 1, the pre-sintering temperatures of samarium sesquioxide and magnesium oxide are 1100°C and 900°C respectively, and the pre-sintering time is 2 hours.

[0021] Furthermore, in Step 2, the mass ratio of the mixture: absolute ethanol: grinding balls is 1:(1.5 to 2.5):(4 to 6), the ball milling time is 5 to 7 hours, and the rotational speed of the planetary ball mill is 220 to 280 revolutions per minute.

[0022] Furthermore, in Step 3, the drying temperature is 80 to 120°C, and the sieving is through a 100-mesh nylon sieve.

[0023] Furthermore, in Step 4, the pressure for manually pressing the green compact is 5 MPa, the pressure of the cold isostatic press is 200 MPa, and the pressure holding time is 3 minutes.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention uses a traditional solid-state sintering method to produce a rare earth oxide-based microwave dielectric ceramic material (1-x)Sm 2 O 3 –xMgO, where x is the mass fraction and 0.10 ≤ x ≤ 0.25. By adding magnesium oxide, the aging decomposition of samarium oxide-based ceramics is inhibited. Further, by adjusting the addition amount, near-zero adjustment of the resonance frequency temperature coefficient is achieved while ensuring a high Q×f value.

[0026] 2. The microwave dielectric ceramic material of the present invention does not contain volatile toxic metals such as Pb and Cd, and can be widely used in microwave devices such as dielectric resonators, filters, and oscillators in satellite communications. It is green, environmentally friendly, and pollution-free, meeting the strict standard requirements of the latest RHOS (Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment) and Waste Electrical and Electronic Equipment (WEEE) regulations issued by the European Community.

[0027] 3. The raw materials for preparing the microwave dielectric ceramic material of the present invention are abundantly supplied in the country and relatively inexpensive, making it possible to achieve low cost for high-performance microwave ceramics. Therefore, it has important industrial application value. Moreover, the sintering temperature of the microwave dielectric ceramic material of the present invention is 1400-1600 °C, and the sintering temperature range is relatively wide, having good process adaptability.

[0028] 4. All the raw materials used in the formula of the present invention are simple oxides, and the ceramic can be sintered in one step, with a simple process. Brief Description of the Drawings

[0029] Figure 1 is the XRD pattern of the microwave dielectric ceramic material prepared in Example 3 of the present invention.

[0030] Figure 2 is the surface SEM image of the microwave dielectric ceramic material prepared in Example 3 of the present invention.

[0031] Figure 3 is the graph of the performance change of the microwave dielectric ceramic materials prepared in Examples 1-4 of the present invention. Detailed Embodiments

[0032] The following specific examples illustrate the embodiments of the present invention. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0033] Example 1

[0034] Step 1: Weighing; The raw material powders of samarium oxide and magnesium oxide are pre-fired at 1100 °C and 900 °C for 2 hours respectively to remove water vapor; According to the chemical formula 0.90Sm 2 O 3 –0.10MgO (x = 0.10), weigh the raw materials of samarium oxide and magnesium oxide for batching to form a mixture;

[0035] Step 2: Ball milling; Using zirconia balls as the ball milling medium and anhydrous ethanol as the dispersion medium, carry out ball milling in a nylon tank for 6 hours according to the mass ratio of the mixture: anhydrous ethanol: grinding balls of 1:2:5. The rotation speed of the planetary ball mill is 250 revolutions per minute to obtain a uniformly mixed slurry;

[0036] Step 3: Drying and sieving; Dry the slurry obtained in Step 2 at 80 °C and pass it through a 100-mesh nylon sieve to obtain a dry powder;

[0037] Step 4: Granulation and tabletting; 5 wt% polyvinyl alcohol solution was added to the dried powder obtained in Step 3 for granulation. The granulated powder was initially pressed into a green body at 5 MPa using a manual tabletting machine, and then further pressed at 200 MPa in a cold isostatic press for 3 minutes under pressure.

[0038] Step 5: The green body pressed in Step 4 was debound at 600 °C for 2 hours.

[0039] Step 6: The green body after debinding in Step 5 was sintered at 1550 °C for 4 hours to prepare 0.90Sm 2 O 3 –0.10MgO microwave dielectric ceramics.

[0040] Example 2

[0041] The samarium oxide-based microwave dielectric ceramics were prepared by the method of Example 1, except that x = 0.15.

[0042] Example 3

[0043] The samarium oxide-based microwave dielectric ceramics were prepared by the method of Example 1, except that x = 0.20.

[0044] Example 4

[0045] The samarium oxide-based microwave dielectric ceramics were prepared by the method of Example 1, except that x = 0.25.

[0046] The dielectric constant ε r , quality factor Q×f and resonant frequency temperature coefficient τ f of the samarium oxide-based microwave dielectric ceramics prepared in Examples 1-4 were tested; among them, ε r and Q×f were measured by a dielectric resonator combined with a vector network analyzer (Agilent E5071C), and τ f was measured by a high and low temperature test chamber combined with a vector network analyzer.

[0047] Figure 1 is the XRD pattern of the microwave dielectric ceramic material prepared in Example 3. It can be seen from Figure 1 that the diffraction peak near 2θ = 43° is the magnesium oxide phase, and the remaining diffraction peaks match well with the monoclinic samarium sesquioxide phase. In addition, there is no sign of the existence of other impurity phases.

[0048] Figure 2 is the surface SEM image of the microwave dielectric ceramic material prepared in Example 3. No cracks were found in the figure, indicating good chemical stability; the black dot-like substances in the figure are magnesium oxide.

[0049] Figure 3Performance change diagram of the microwave dielectric ceramic materials prepared in Examples 1-4. It can be seen from Figure 2 that as the addition amount of magnesium oxide increases, the dielectric constant ε r shows a downward trend, decreasing from 20.0 at x = 0.10 to 16.2 at x = 0.25; the quality factor Q×f shows an upward trend, increasing from 49,700 GHz at x = 0.10 to 63,600 GHz at x = 0.25; the temperature coefficient of resonant frequency τ f shows a downward trend, and τ f is nearly zero at x = 0.20, being +0.4 ppm / °C.

[0050] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A rare earth oxide-based microwave dielectric ceramic material with both chemical and temperature stability, characterized in that , The systematic chemical formula is (1-x)Sm 2 O 3 –xMgO; where x is the mass fraction and 0.10 ≤ x ≤ 0.25; no aging and decomposition phenomenon is observed when exposed to air; the dielectric constant ε r is 20.0 to 16.2, the quality factor Q×f is 49,700 to 63,600 GHz, and the resonant frequency temperature coefficient τ f is +15.3 to -6.3 ppm / °C; and it is prepared by the following steps: Step 1: Mixing ingredients; pre-burning samarium trioxide and magnesium oxide raw material powder to remove moisture; according to the chemical formula (1-x) Sm 2 O 3 –xMgO, x is the mass fraction and 0.10≤x≤0.

25. Weigh samarium trioxide and magnesium oxide raw materials and mix them to form a mixture; Step 2: Ball milling; Using zirconia balls as the ball milling medium and anhydrous ethanol as the dispersing medium, put the raw materials, anhydrous ethanol, and grinding balls into a nylon pot, and perform ball milling on a planetary ball mill to obtain a uniformly mixed slurry; Step 3: Drying and sieving; Dry and sieve the slurry obtained in Step 2 to obtain a dry powder; Step 4: Granulation and tabletting; Add a 5wt% polyvinyl alcohol solution to the dry powder obtained in Step 3 for granulation, and initially tablet the granulated powder into a green body with a manual tablet press, and then further press it with a cold isostatic press; Step 5: Debind the green body pressed in Step 4 at 500°C to 600°C for 1.5 to 2.5 hours; Step 6: Sinter the green body after debinding in Step 5 at a temperature ranging from 1400 °C to 1600 °C for a holding time of 4 to 6 hours to fabricate a (1-x)Sm 2 O 3 –xMgO microwave dielectric ceramic, where x is the mass fraction and 0.10 ≤ x ≤ 0.

25.

2. A rare earth oxide-based microwave dielectric ceramic material with both chemical and temperature stability according to claim 1, characterized in that ,x＝0.20。 3. A preparation method of a rare earth oxide-based microwave dielectric ceramic material with both chemical and temperature stability according to any one of claims 1-2, characterized in that, this method is carried out according to the following steps: Step 1: Batching; Pre-calcining the raw material powders of samarium sesquioxide and magnesium oxide to remove moisture; According to the chemical formula (1-x)Sm 2 O 3 –xMgO, where x is the mass fraction and 0.10 ≤ x ≤ 0.25, weighing the raw materials of samarium sesquioxide and magnesium oxide for batching to form a mixture; Step 2: Ball milling; Using zirconia balls as the ball milling medium and anhydrous ethanol as the dispersing medium, put the raw materials, anhydrous ethanol, and grinding balls into a nylon pot, and perform ball milling on a planetary ball mill to obtain a uniformly mixed slurry; Step 3: Drying and sieving; Dry and sieve the slurry obtained in Step 2 to obtain a dry powder; Step 4: Granulation and tabletting; Add a 5wt% polyvinyl alcohol solution to the dry powder obtained in Step 3 for granulation, and initially tablet the granulated powder into a green body with a manual tablet press, and then further press it with a cold isostatic press; Step 5: Debind the green body pressed in Step 4 at 500°C to 600°C for 1.5 to 2.5 hours; Step 6: Sinter the green body after debinding in Step 5 within the range of 1400°C to 1600°C, with a holding time of 4 to 6 hours, to produce (1-x)Sm 2 O 3 –xMgO microwave dielectric ceramics, where x is the mass fraction and 0.10 ≤ x ≤ 0.

25.

4. A preparation method of a rare earth oxide-based microwave dielectric ceramic material with both chemical and temperature stability according to claim 3, characterized in that , the pre-burning temperatures of samarium sesquioxide and magnesium oxide in Step 1 are 1100°C and 900°C respectively, and the pre-burning time is 2 hours.

5. A preparation method of a rare earth oxide-based microwave dielectric ceramic material with both chemical and temperature stability according to claim 3, characterized in that , the mass ratio of the mixture: anhydrous ethanol: grinding balls in Step 2 is 1:(1.5 - 2.5):(4 - 6), the ball milling time is 5 - 7 hours, and the rotation speed of the planetary ball mill is 220 - 280 revolutions per minute.

6. A preparation method of a rare earth oxide-based microwave dielectric ceramic material with both chemical and temperature stability according to claim 3, characterized in that , the drying temperature in Step 3 is 80 - 120°C, and the sieving is through a 100-mesh nylon sieve.

7. A preparation method of a rare earth oxide-based microwave dielectric ceramic material with both chemical and temperature stability according to claim 3, characterized in that , the pressure for manually pressing the green body in Step 4 is 5MPa, the pressure of the cold isostatic press is 200MPa, and the pressure holding time is 3 minutes.

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