Novel single-phase molybdate high-entropy ceramic material and preparation method thereof

Abstract

The invention provides a novel single-phase molybdate high-entropy ceramic material and a preparation method thereof, belongs to the field of electronic ceramics and manufacturing thereof, and particularly relates to the novel single-phase molybdate high-entropy ceramic material and the preparation method thereof. The chemical formula of the material is Sr0. 2Ba0. 2Ca0. 2Na0. 2Bi0. 2MoO4. The material is prepared from the following raw materials: SrCO3, BaCO3, CaCO3, Na2CO3, Bi2O3 and MoO3 through a solid-phase sintering method, and has a low dielectric constant (epsilon r is equal to 10.29), a temperature coefficient of resonance frequency (-37 ppm / DEG C) close to 0 and a high quality factor (42002GHz). The high-entropy ceramic is prepared by performing A-site doping on multiple elements on the basis of traditional SrMoO4, the temperature coefficient of resonance frequency is improved while low dielectric constant and low dielectric loss are guaranteed, the high-entropy ceramic is suitable for electronic substrates and packaging materials, the preparation method is simple, and industrial production is easy.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic ceramics and their manufacturing technologies, and particularly relates to a novel single-phase molybdate high-entropy ceramic material and a preparation method thereof. Background Art

[0002] With the continuous progress of communication technologies, microwave communication systems are developing towards lower power consumption, higher data transmission speeds, and smaller sizes. Microwave dielectric ceramics are important materials for passive components used in microwave communication systems. The integration and miniaturization of electronic components in microwave dielectric ceramics require low dielectric constant (ε r ), high quality factor (Q×f), and a resonance frequency temperature coefficient (TCF) close to zero during the dense ceramic sintering process. However, dielectric ceramics with low dielectric constant and high Q×f usually have a lower negative temperature coefficient of resonance frequency. Due to the inherent interdependence of these three key dielectric parameters, only a few materials exhibit ideal microwave dielectric properties. Therefore, developing new materials with low dielectric constant, low dielectric loss, and near-zero TCF that can meet the strict standards of microwave communication systems remains a major challenge.

[0003] Among many electronic ceramics, molybdate-based ceramics have received extensive attention due to their low dielectric loss and low dielectric constant, and have played an important role in the manufacture of electronic components. Among them, SrMoO4 has good microwave dielectric properties: ε r ≈9.49, Q×f≈61000 GHz, τ f =-67.17 ppm / °C. However, the lower resonance frequency temperature coefficient cannot meet the current requirements for miniaturization and integration of electronic components. Therefore, there is an urgent need to develop microwave dielectric ceramics with low dielectric constant, high quality factor, and a resonance frequency temperature coefficient close to zero. Summary of the Invention

[0004] Aiming at the above problems, the present invention aims to improve the dielectric properties of SrMoO4-based ceramics, develop a ceramic material with low dielectric constant, high quality factor, and near-zero resonance frequency temperature coefficient, and provides a novel single-phase molybdate high-entropy ceramic material and a preparation method thereof.

[0005] The present invention adopts the following technical solutions:

[0006] 1. A novel single-phase molybdate high-entropy ceramic material, the chemical general formula of the material is Sr 0.2 Ba 0.2 Ca 0.2 Na 0.2 Bi 0.2MoO4, with the raw material composition of SrCO3, BaCO3, CaCO3, Na2CO3, Bi2O3 and MoO3, is synthesized by the solid-phase method: when the sintering temperature is 1050 °C, it has a low dielectric constant (ε r = 10.29), a near-zero temperature coefficient of resonant frequency (-37 ppm / °C), and a high quality factor (42002 GHz).

[0007] The specific preparation method is as follows:

[0008] Step 1: Weigh the raw powders of high-purity SrCO3, BaCO3, CaCO3, Na2CO3, Bi2O3 and MoO3 according to the chemical formula Sr 0.2 Ba 0.2 Ca 0.2 Na 0.2 Bi 0.2 MoO4 for batching;

[0009] Step 2: Ball mill the batch prepared in Step 1 for 8 hours according to the mass ratio of powder, zirconia balls, and distilled water of 1:5:1. After taking it out, dry it at 110 °C and sieve it through a 200-mesh sieve. Place the sieved powder in a high-temperature muffle furnace and pre-burn it at 650 °C for 4 hours. The pre-burned powder is ball milled for another 8 hours, dried, and then 8% polyvinyl alcohol aqueous solution is added for granulation, and it is sieved through a 200-mesh sieve to ensure that the particles are small and uniform;

[0010] Step 3: Use a tablet press to press the granulated powder into a 12 mm × 6 mm cylinder at 20 MPa. Place the pressed cylinder in a muffle furnace and keep it at 650 °C for two hours for degumming, and then sinter it at 900 - 1050 °C for 4 hours to obtain a single-phase molybdate high-entropy ceramic material.

[0011] The present invention utilizes the severe lattice distortion and microstrain of high-entropy ceramics. High lattice distortion and microstrain are beneficial to improving the temperature coefficient of resonant frequency. Secondly, high-entropy ceramics inhibit ion diffusion by changing the diffusion path and increasing the diffusion barrier, resulting in the phenomenon of retarded diffusion. The retarded diffusion can effectively reduce the migration loss to compensate for the increased loss caused by severe lattice distortion. At the same time, the retarded diffusion of high-entropy ceramics can inhibit the abnormal growth of grain size to avoid excessive reduction of dielectric loss. When the sintering temperature of high-entropy ceramics reaches 1050 °C, a new type of single-phase molybdate high-entropy ceramic material is finally prepared.

[0012] The preparation method is traditional pressureless sintering. On the premise of low cost and simple process, it can greatly improve the microwave dielectric properties of SrMoO4 and is suitable for mass production.

[0013] In summary, the novel single-phase molybdate high-entropy ceramic provided by the present invention has a dense microstructure, high quality factor, low dielectric constant and near-zero resonance frequency temperature coefficient, and has great prospects in the application materials of electronic substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0015] Figure 1 X-ray diffraction for Examples 1-4;

[0016] Figure 2 Microscopic morphology and average grain size for Examples 1-4;

[0017] Figure 3 Density and relative density for Examples 1-4;

[0018] Figure 4 Microwave dielectric properties for Examples 1-4; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] As Figures 1 to 2 shown, the present invention will be described in detail below with reference to the accompanying drawings and examples.

[0021] The chemical formula of the material of the present invention is Sr 0.2 Ba 0.2 Ca 0.2 Na 0.2 Bi 0.2 MoO4, and this material is prepared by the solid-phase method, and the specific steps are the same as the above steps.

[0022] The xrd patterns ( Figure 1 ) of the high-entropy ceramic samples of different examples were analyzed, and it was found that they all had a tetragonal scheelite structure at different sintering temperatures. At 900 °C (Example 1), Ba 0.5 Sr 0.5 MoO4 and Sr 0.5 Ca 0.5 MoO4 phases were formed. In the range of 950 °C (Example 2), Ba 0.3 Ca 0.2 Sr 0.5 MoO4 and Sr 0.5Ca 0.5 The BaMoO4 phase appears within the range of 1000 °C (Example 3). 0.3 Ca 0.2 Sr 0.5 MoO4 and Sr 0.5 Ca 0.5 MoO4 phase. When the temperature reaches 1050 °C (Example 4), single-phase Sr 0.5 Ca 0.5 MoO4 is obtained.

[0023] Figure 2 (a - d) and (e - h) of [subject not clear] show the SEM microtopographies of Samples 1 to 4. As the sintering temperature increases, the porosity of the samples gradually decreases, and the densification of the ceramics is significantly enhanced. This phenomenon can be attributed to the promotion of grain growth at high temperatures, which in turn promotes the migration of grain boundaries, resulting in pore shrinkage. It can be seen from the average grain size of the high-entropy ceramics that as the sintering temperature increases, the grain size gradually increases, effectively eliminating the pores in the material. This trend indicates that high-temperature sintering not only promotes grain growth but also further refines the microstructure of the material, thereby improving its overall performance. It should be noted that the average grain size shows a slow increasing trend, which is closely related to the retarded diffusion of the high-entropy ceramics.

[0024] Figure 3 Shows the density and relative density of Samples 1 to 4. As the sintering temperature increases, both the density and relative density gradually increase. This is because, as the sintering temperature increases, the accelerated grain growth promotes the migration of grain boundaries, resulting in pore shrinkage, thereby increasing the density. Sample 4 exhibits the highest density and relative density, indicating that Sample 4 has a denser microstructure.

[0025] Figure 4 Shows the microwave dielectric properties of Samples 1 to 4. As the sintering temperature increases, the dielectric constant of the samples gradually decreases, the dielectric loss gradually decreases, and the temperature coefficient of resonant frequency gradually increases. The increase in the temperature coefficient of resonant frequency is closely related to the microstrain and lattice distortion rate. Overall, when the sintering temperature reaches 1050 °C, the best microwave dielectric properties are obtained: ε r = 10.29, τ f = -37 ppm / °C, Q×f = 42002 GHz.

[0026] In summary, the present invention prepares a novel single-phase molybdate high-entropy ceramic by the solid-phase method. By adjusting the sintering temperature and testing the properties to obtain the best performance (Example Sample 4), the density, relative density, and temperature coefficient of resonant frequency can be significantly improved. It is suitable for electronic packaging substrate materials, has low requirements for production conditions, and is easy to industrialize and mass-produce.

[0027] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A novel single-phase molybdate high-entropy ceramic material, characterized in that, The base formula is SrCO3, BaCO3, CaCO3, Na2CO3, Bi2O3 and MoO3, which is prepared by the solid-phase method: having a low dielectric constant (ε r = 10.29), a near-zero temperature coefficient of resonant frequency (-37 ppm / °C), and a high quality factor (42002 GHz).

2. The preparation method of the novel single-phase molybdate high-entropy ceramic material according to claim 1, characterized in that, The details are as follows: Step 1: Weigh the raw powders of high-purity SrCO3, BaCO3, CaCO3, Na2CO3, Bi2O3 and MoO3 according to the chemical formula Sr 0.2 Ba 0.2 Ca 0.2 Na 0.2 Bi 0.2 to prepare MoO4 Step 2: Ball mill the ingredients prepared in Step 1 for 8 hours according to the mass ratio of powder material, zirconia balls, and distilled water of 1:5:

1. After taking out, dry it at 110°C and sieve it through a 200-mesh sieve. Place the sieved powder in a high-temperature muffle furnace and pre-burn it at 650°C for 4 hours. The pre-burned powder is ball milled for another 8 hours, dried, and then granulated by adding an 8% aqueous solution of polyvinyl alcohol and sieved through a 200-mesh sieve to ensure that the particles are fine and uniform; Step 3: Use a tablet press to press the granulated powder material into a cylinder with a size of 12 mm × 6 mm under a pressure of 20 MPa. Place the pressed cylinder in a muffle furnace and keep it at 650°C for two hours for debinding, and then sinter it at 900 - 1050°C for 4 hours to obtain a single-phase molybdate high-entropy ceramic material.

Images