Olivine type lithium-containing silicon-based compact ceramic and preparation method thereof

Abstract

The invention provides olivine type lithium-containing silicon-based compact ceramic and a preparation method thereof. The chemical general formula of the lithium-containing silicon-based compact ceramic is LiIn1-xMxSiO4 (x is greater than or equal to 0.35 and less than or equal to 0.8), M must contain a Yb element and also comprises at least one element of Zn, Ni, Ga, Y, Eu, Ho, Er and Tm, and the sum of lower corner marks of the elements in M is equal to the value of x. According to the method, a traditional solid-phase reaction sintering method is adopted, the process is simple, and the olivine type lithium-containing silicon-based compact ceramic with excellent comprehensive microwave dielectric properties can be obtained under the condition of not additionally adding a sintering aid or carrying out hot pressing sintering.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic functional ceramics, and in particular relates to a lithium-containing silicon-based dense ceramic with an olivine structure and a preparation method thereof. Background Art

[0002] With the promotion of 5G technology and the layout of 6G technology, microwave communication technology will extend to the millimeter wave band. Electronic components with low dielectric constant microwave dielectric ceramics as key basic materials have the characteristics of fast signal transmission response and low dielectric loss at high frequencies, and are widely used in substrates, dielectric filters, dielectric resonators and other fields.

[0003] Olivine type (chemical formula is ABCO4) microwave dielectric ceramics are a type of dielectric constant (ε r ) are generally low microwave dielectric materials, among which forsterite Mg2SiO4 has an ultra-high quality factor (Q×f value), but Mg2SiO4 and its modified series of silicon-based olivine ceramics have a very high sintering temperature (1300℃~1500℃), which is not conducive to the application of low-temperature co-firing technology; germanium-based olivine such as CaMgGeO4, Ca2GeO4, Mg2GeO4, NaYGeO4 and other sintering temperatures are relatively low compared to silicon-based olivine (1200℃~1450℃), but the raw material GeO2 is expensive, which is not conducive to large-scale production; and LiMgPO4 and its modified series of phosphorus-based olivine are easy to absorb moisture and have a low resonant frequency temperature coefficient (τ f ) is generally larger in the negative direction (-60 to -90 ppm / ℃) and requires a complex modification process to meet practical needs.

[0004] Olivine-type LiASiO4 microwave dielectric ceramics are a series of low dielectric microwave dielectric ceramics with moderate sintering temperature (1050℃~1150℃). For example, LiInSiO4 has a certain potential microwave dielectric performance ε at 1150℃. r =8.2, Q×f=12600GHz, τ f=-55ppm / ℃; however, due to its low density (relative density ≤91%), its Q×f value is relatively low. After adding sintering aids, the microstructure of the ceramic is effectively improved, the density is significantly improved, and the Q×f value can reach up to 22000GHz (J.Alloys Compd.552(2013)83-87). In addition, lithium-containing silicon-based olivine LiYbSiO4(Ceram.Int.46(2020)19996–20003), LiHoSiO4(Ceram.Int.50(2024)31278-31286) and LiTmSiO4(J.Mater.Sci.Mater.Electron.(2024)35:1468) with low dielectric constants also have lower sintering temperatures and smaller τ f However, their Q×f values ​​are slightly insufficient (the highest is only 25276 GHz) due to their less than ideal relative density (<95%).

[0005] In fact, it is difficult to obtain dense microstructure and relative density by using ordinary high-temperature solid-phase reaction method to prepare lithium-containing silicate ceramics without any sintering aid or hot pressing sintering. This is mainly due to the large difference in melting points of Li2O and SiO2. + It is easy to volatilize at high temperature, resulting in the formation of many pores in the ceramic microstructure, which ultimately leads to low density of ceramic samples. In addition to lithium-containing silicon-based olivine, other lithium-containing silicates such as LiGaSiO4 (Ceram.Int.50(2024)7758-7766), Li(Zn 0.95 Co 0.05 ) 1.5 SiO4 (Ceram.Int.43 (2017) 7636-7640) and LiRe9(SiO4)6O2 (J.Am.Ceram.Soc.96 (2013) 1504–1511) also exhibit lower Q×f values ​​due to their undesirable relative density (<95%).

[0006] High entropy ceramics mainly refer to single-phase solid solution ceramics formed by four or more ceramic components. High entropy ceramics have the characteristics of high entropy effect, lattice distortion effect, cocktail effect and hysteresis diffusion effect, which makes high entropy ceramics have higher hardness, strength, wear resistance, thermal stability and lower thermal conductivity than traditional single-component ceramics. However, there is no clear understanding whether high entropy ceramics must achieve higher density. The literature points out that in a series of fluorite-structured high entropy ceramics, (Hf 0.25 Zr 0.25 Ce 0.25 )(Y 0.125 Ca 0.125 )2-δ The relative density can reach 98.5%, but (Hf 0.2 Zr 0.2 Ce 0.2 )(Y 0.2 Yb 0.2 ) 2-δ The relative density of Hf is only 93.7%. 0.25 Zr 0.25 Ce 0.25 )(Yb 0.125 G 0.125 ) 2-δ and (Hf 0.2 Zr 0.2 Ce 0.2 )(Yb 0.2 G 0.2 ) 2-δ The relative density is as low as 77.8% and 68.4% (J. Eur. Ceram. Soc. 38 (2018) 3578-3584). In addition to the above-mentioned high entropy oxide ceramics, Gild also found that their relative density in a series of high entropy borate ceramics was lower than 92.5% (Scientific Reports 6: 37946 (2016)).

[0007] At present, there are few studies on olivine-type high-entropy LiASiO4, and as mentioned above, high-entropy ceramics do not necessarily have higher relative density than single-element ceramics. How to obtain olivine-type lithium-containing silicon-based ceramics with a relative density greater than 95% and excellent microwave dielectric properties is a challenging problem, and solving this problem will also provide valuable reference significance for the densification of other lithium-containing silicates. Summary of the invention

[0008] In order to solve the above problems, the purpose of the present invention is to provide an olivine-type lithium-containing silicon-based dense ceramic and a preparation method thereof. The present invention mainly takes olivine-type LiInSiO4 as the object, and replaces In with two or more metal cations. 3+ As the basic idea, non-equimolar ratio components or equimolar ratio components are used to occupy In 3+ The design of the high-entropy lithium-containing silicon-based olivine can prepare dense ceramics through a simple traditional high-temperature solid-phase synthesis method without the need for hot pressing and sintering, and reduces the amount of expensive In2O3, ultimately obtaining olivine-type lithium-containing silicon-based dense ceramics with a series of excellent comprehensive microwave dielectric properties.

[0009] In order to overcome the deficiencies in the prior art, the technical solution of the present invention is:

[0010] An olivine-type lithium-containing silicon-based dense ceramic, characterized in that the chemical formula of the lithium-containing silicon-based dense ceramic is LiIn 1-x M x SiO4 (0.35≤x≤0.8), wherein M must contain Yb and also contains at least one element from Zn, Ni, Ga, Y, Eu, Ho, Er, Tm, and the sum of the subscripts of the elements in M ​​is equal to the value of x. The relative dielectric constant of the olivine-type lithium-containing silicon-based dense ceramic is ε r is 7.49~7.88, the quality factor Q×f is 15440~30770GHz, and the resonant frequency temperature coefficient τ f The olivine-type lithium-containing silicon-based dense ceramic is characterized in that the sintering temperature range of the lithium-containing silicon-based dense ceramic is between 1050°C and 1110°C; when the chemical formula of the lithium-containing silicon-based dense ceramic is LiIn 0.65 Yb 0.2 Ga 0.15 When SiO4, the ceramic has a second phase In2O3 in addition to the main phase olivine; when the chemical formula of the lithium-containing silicon-based dense ceramic is Li(InYb) 0.4 (GaEu) 0.1 SiO4, the ceramic has two impurity phases in addition to the main phase olivine, one of which is In2O3; when the chemical formula of the lithium-containing silicon-based dense ceramic is LiIn 0.3 (GaYEuHoErYbTm) 0.1 When SiO4, the ceramic has two impurity phases in addition to the main phase olivine, one of which is In2O3; when the chemical formula of the lithium-containing silicon-based dense ceramic is Li(InYb) 0.3 (GaEuHoTm) 0.1 When SiO4 is used, the ceramic has a mixed phase in addition to the main phase olivine.

[0011] The preparation method of the olivine-type lithium-containing silicon-based dense ceramic comprises the following steps:

[0012] (1) weighing Li2CO3, In2O3, SiO2 and metal oxide M according to the general chemical formula and mixing them together to form a raw material mixture;

[0013] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0014] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0015] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0016] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0017] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1050°C to 1110°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0018] Preferably, the sintering process in step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0019] Compared with the prior art, the advantages of the present invention are: the material provided by the present invention has a low dielectric constant (7.49-7.88) which can reduce the signal delay time, a generally high quality factor (15440-30770GHz) which can improve the selectivity of the device operating frequency, and a smaller τ f The ceramic preparation process of the present invention adopts the traditional high-temperature solid-phase synthesis method, and the sintering temperature is lower than 1120°C. The process is simple and does not require the addition of additional sintering aids or hot pressing sintering to obtain olivine-type lithium-containing silicon-based dense ceramics with excellent comprehensive microwave dielectric properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Olivine-type lithium-containing silicon-based LiIn 1-x M x XRD pattern of SiO4 (0.35≤x≤0.8; where M must contain Yb element and also includes at least one element from Zn, Ni, Ga, Y, Eu, Ho, Er, Tm) ceramics;

[0021] Figure 2 For LiIn 0.5 Yb 0.4 Ga 0.1 Microscopic morphology of SiO4 ceramics;

[0022] Figure 3 Li(InYb) 0.3 (GaEuHoTm) 0.1 Microscopic morphology of SiO4 ceramics. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0024] Embodiment 1:

[0025] (1) According to the chemical formula LiIn 0.2 Yb 0.7 Ga 0.1 Proportion of SiO4 Weigh Li2CO3, In2O3, SiO2, Yb2O3 and Ga2O3 and mix them together to form a raw material mixture;

[0026] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0027] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0028] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0029] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0030] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1110°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0031] In this specific embodiment, the sintering process of step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0032] Embodiment 2:

[0033] (1) According to the chemical formula LiIn 0.2 Yb 0.65 Ni 0.15 Proportion of SiO4 Weigh Li2CO3, In2O3, SiO2, Yb2O3 and NiO and mix them together to form a raw material mixture;

[0034] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0035] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0036] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0037] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0038] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1100°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0039] In this specific embodiment, the sintering process of step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0040] Example 3

[0041] (1) According to the chemical formula LiIn 0.2 Yb 0.65 Zn 0.15 Proportion of SiO4 Weigh Li2CO3, In2O3, SiO2, Yb2O3 and ZnO and mix them together to form a raw material mixture;

[0042] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0043] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0044] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0045] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0046] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1050°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0047] In this specific embodiment, the sintering process of step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0048] Example 4

[0049] (1) According to the chemical formula LiIn 0.5 Yb 0.4 Ga 0.1 Proportion of SiO4 Weigh Li2CO3, In2O3, SiO2, Yb2O3 and Ga2O3 and mix them together to form a raw material mixture;

[0050] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0051] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0052] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0053] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0054] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1100°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0055] In this specific embodiment, the sintering process of step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0056] Example 5

[0057] (1) According to the chemical formula Li(InYb) 0.3 (GaEuHoTm) 0.1 Proportion of SiO4 Weigh Li2CO3, In2O3, SiO2, Yb2O3, Ga2O3, Eu2O3, Ho2O3 and Tm2O3 and mix them together to form a raw material mixture;

[0058] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0059] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0060] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0061] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0062] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1090°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0063] In this specific embodiment, the sintering process of step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0064] Example 6

[0065] (1) According to the chemical formula LiIn 0.65 Yb 0.2 Ga 0.15 Proportion of SiO4 Weigh Li2CO3, In2O3, SiO2, Yb2O3 and Ga2O3 and mix them together to form a raw material mixture;

[0066] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0067] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0068] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0069] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0070] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1090°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0071] In this specific embodiment, the sintering process of step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0072] Example 7

[0073] (1) According to the chemical formula Li(InYb) 0.4 (GaEu) 0.1 Proportion of SiO4 Weigh Li2CO3, In2O3, SiO2, Yb2O3, Ga2O3 and Eu2O3 and mix them together to form a raw material mixture;

[0074] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0075] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0076] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0077] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0078] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1110°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0079] In this specific embodiment, the sintering process of step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0080] Example 8

[0081] (1) According to the chemical formula LiIn 0.3 (GaYEuHoErYbTm) 0.1 Proportion of SiO4 Li2CO3, In2O3, SiO2, Yb2O3, Ga2O3, Eu2O3, Y2O3, Ho2O3, Er2O3 and Tm2O3 were weighed and mixed together to form a raw material mixture;

[0082] (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder;

[0083] (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material;

[0084] (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder;

[0085] (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder;

[0086] (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1070°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

[0087] In this specific embodiment, the sintering process of step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

[0088] The ceramics obtained by sintering Examples 1 to 8 were tested by XRD, and the results are as shown in the attached Figure 1 As shown in Figure 2, the physical phases of these ceramics are all olivine structural phases. 0.65 Yb 0.2 Ga 0.15 In addition to the main phase olivine, SiO4 ceramics also have a second phase In2O3; Li(InYb) 0.4 (GaEu) 0.1 In addition to the main phase olivine, SiO4 ceramics also have two impurity phases, one of which is In2O3; LiIn 0.3 (GaYEuHoErYbTm) 0.1 In addition to the main phase olivine, SiO4 ceramics also have two impurity phases, one of which is In2O3; Li(InYb) 0.3 (GaEuHoTm) 0.1 In addition to the main phase olivine, SiO4 ceramics also have a mixed phase.

[0089] The apparent density of the ceramics obtained by sintering Examples 1 to 8 was tested by the Archimedean drainage method, and then refined by the XRD data corresponding to each ceramic. The theoretical density was calculated based on the refined results, and finally the relative density of the ceramic was calculated based on the apparent density and the theoretical density. The results are shown in Table 1. The ceramics in each example have a relatively high relative density. In addition to the potential possibility that multiple cations occupy the same lattice position, the densification may also be related to the ceramic body prepared by mixing large and small powder particles in a certain mass ratio after granulation and screening during the preparation process. In addition, Table 1 shows the microwave dielectric properties of each specific example. Combined with Figure 1 From the XRD results, when the impurity phase appears, or even when there are multiple impurity phases, the ceramic samples show lower Q×f values, which may be related to the impurity phase.

[0090] Figure 2 LiIn in Example 40.5 Yb 0.4 Ga 0.1 Microscopic morphology of SiO4 ceramics. It can be seen from the figure that ceramics with different grain sizes but clear grain boundaries and compact and dense micromorphology can be prepared by traditional high-temperature solid-phase synthesis. It can be inferred from the relative density and microscopic morphology that when a certain molar ratio of In 3+ , Yb 3+ and Ga 3+ When they occupy the same lattice position together, they can promote the densification of ceramics, which in turn helps to improve the Q×f value of the ceramics.

[0091] Figure 3 is Li(InYb) in Example 5 0.3 (GaEuHoTm) 0.1 Microscopic morphology of SiO4 ceramics. It can also be seen from the figure that the traditional high-temperature solid-phase synthesis method can also be used to prepare ceramics with compact grain distribution and relatively dense microscopic morphology. It can be inferred from the relative density and microscopic morphology that when a certain molar ratio of In 3+ , Yb 3+ , Ga 3+ 、Eu 3+ 、Ho 3+ and Tm 3+ When they occupy the same lattice position, the high entropy ceramics formed may grow slowly due to the hysteresis diffusion effect at high temperature, which is conducive to the densification of the ceramics. However, it may be due to the presence of a small amount of impurities, Li(InYb) 0.3 (GaEuHoTm) 0.1 The Q×f value of SiO4 ceramics is not high enough.

[0092] Table 1

[0093]

[0094] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the scope of patent protection determined by the claims submitted by the present invention.

Claims

1. An olivine-type lithium-containing silicon-based dense ceramic, characterized in that: The chemical formula of the lithium-containing silicon-based dense ceramic is LiIn 1-x M x SiO4 (0.35≤x≤0.8), where M must contain Yb element and also includes at least one element from Zn, Ni, Ga, Y, Eu, Ho, Er, Tm, and the sum of the subscripts of the elements in M ​​is equal to the value of x.

2. The lithium-containing silicon-based dense ceramic according to claim 1, characterized in that: The relative dielectric constant ε of the lithium-containing silicon-based dense ceramic is r It is 7.49~7.88, and the quality factor Q×f is 15440~30770GHz.

3. The lithium-containing silicon-based dense ceramic according to claim 1, characterized in that: The resonant frequency temperature coefficient τ of the lithium-containing silicon-based dense ceramic f Between -40.4ppm / ℃ and -14.6ppm / ℃.

4. The lithium-containing silicon-based dense ceramic according to claim 1, characterized in that: The sintering temperature of the lithium-containing silicon-based dense ceramic is in the range of 1050°C to 1110°C.

5. The lithium-containing silicon-based dense ceramic according to claim 1, characterized in that: When the number of elements M in the lithium-containing silicon-based dense ceramic is 2, and the chemical formula is LiIn 0.65 Yb 0.2 Ga 0.15 When SiO4 is used, the ceramic has a second phase In2O3 in addition to the main phase olivine.

6. The lithium-containing silicon-based dense ceramic according to claim 1, characterized in that: When the number of elements M in the lithium-containing silicon-based dense ceramic is 3, and the chemical formula is Li(InYb) 0.4 (GaEu) 0.1 When SiO4 is used, the ceramic has two impurity phases besides the main phase olivine, one of which is In2O3.

7. The lithium-containing silicon-based dense ceramic according to claim 1, characterized in that: When the number of M elements in the lithium-containing silicon-based dense ceramic is 7 and the chemical formula is LiIn 0.3 (GaYEuHoErYbTm) 0.1 When SiO4 is used, the ceramic has two impurity phases besides the main phase olivine, one of which is In2O3.

8. The lithium-containing silicon-based dense ceramic according to claim 1, characterized in that: When the number of elements M in the lithium-containing silicon-based dense ceramic is 5 and the chemical formula is Li(InYb) 0.3 (GaEuHoTm) 0.1 When SiO4 is used, the ceramic has a mixed phase in addition to the main phase olivine.

9. A method for preparing a lithium-containing silicon-based dense ceramic according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) weighing Li2CO3, In2O3, SiO2 and metal oxide M according to the general chemical formula and mixing them together to form a raw material mixture; (2) placing the raw material mixture of step 1 in a polytetrafluoroethylene ball mill, using zirconium dioxide balls and anhydrous ethanol as ball milling media, ball milling for 4 hours, and then drying to obtain a mixture powder; (3) pre-sintering the dried mixture powder in a high temperature furnace, that is, heating the mixture from room temperature to 900° C. and keeping the temperature at this temperature for 3 hours, and then cooling the mixture in the furnace to obtain a pre-sintered material; (4) ball milling the pre-sintered material obtained in step 3 using zirconium dioxide balls and anhydrous ethanol as ball milling media for 6 hours, and then drying to obtain a powder; (5) Adding a binder to the powder obtained after drying in step 4, granulating and sieving, during the sieving process, a bottom plate is placed at the bottom, a 120-mesh standard sieve is placed in the middle, and a 60-mesh standard sieve is placed on the top; the powder that passes through the 60-mesh standard sieve and remains on the 120-mesh standard sieve is taken as A powder, and the powder that passes through the 120-mesh standard sieve and remains on the bottom plate is taken as B powder, and then the A powder and the B powder are weighed in a mass ratio of 3:1 and placed in an agate mortar for uniform grinding, and then transferred to a beaker filled with anhydrous ethanol, and then the beaker is placed in an ultrasonic cleaner for ultrasonic dispersion for 10 minutes, and dried to obtain C powder; (6) A portion of the C powder in step 5 is placed in a mold, pressed into a cylinder at 170 MPa and placed in a crucible, and then another portion of the C powder is poured into the crucible as a buried powder so that the buried powder wraps and covers the cylinder. The crucible is then placed in a high-temperature furnace for sintering. The sintering target temperature is 1050°C to 1110°C, and the target temperature is maintained for 5 hours, and then cooled with the furnace to obtain an olivine-type lithium-containing silicon-based dense ceramic.

10. The method for preparing lithium-containing silicon-based dense ceramics according to claim 9, characterized in that: The sintering process in step 6 is divided into two different heating rates. The heating rate before 550°C is 1.5°C / min, and the temperature is kept at 550°C for 1 hour; then the temperature is increased from 550°C to the target temperature, and the heating rate in this heating range is 3°C / min.

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