Green silicon nitride ceramic material and preparation method thereof

Abstract

The invention discloses a green silicon nitride ceramic material and a preparation method thereof, the green silicon nitride ceramic material comprises the following raw materials: 78-95 wt% of silicon nitride, 4-14 wt% of a sintering aid, 1-8 wt% of a coloring agent Pr6O11, and a dispersant accounting for 0.5-5% of the total mass of silicon nitride powder, the coloring agent and the sintering aid; the content of the binder is 0.5%-8% of the total mass of the silicon nitride powder, the coloring agent and the sintering aid, and the content of the plasticizer is 0.5%-6% of the total mass of the silicon nitride powder, the coloring agent and the sintering aid.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silicon nitride advanced ceramics, and particularly relates to a green silicon nitride ceramic material and a preparation method thereof. BACKGROUND

[0002] With the rapid development and popularization of science and technology, terminal communication equipment such as mobile phones and notebook computers play an increasingly important role in daily life. The equipment shell is not only an appearance factor that consumers pay attention to when selecting products, but also plays a key role in protecting internal electronic components and ensuring communication signal transmission. Therefore, it is particularly important to develop a communication battery backboard material that is not only colorful and beautiful, but also has excellent mechanical properties, thermal properties and good electromagnetic shielding properties to meet the growing needs of life and technology.

[0003] Ceramic materials have become a potential shell material choice due to their excellent wear resistance and dielectric properties, which not only meet the aesthetic and functional requirements of high-end products in the market, but also can cope with the challenges brought by new technologies such as 5G. Although the coloring technology of the widely used ZrO2 ceramic is relatively mature, its impact resistance and thermal shock resistance are poor, and its density is high, which leads to an increase in the weight of terminal equipment, making it difficult to meet the current consumer demand for lightweight equipment. Therefore, lightweight silicon nitride (Si3N4) ceramic has gradually become a potential candidate for backboard material due to its lower density and more excellent mechanical properties. However, the color of Si3N4 ceramic is single due to its high sintering temperature and difficulty in coloring, which to some extent limits the selection range of the customer group. SUMMARY

[0004] In order to overcome the deficiencies in the prior art, the present application provides a green silicon nitride ceramic material and a preparation method thereof, and the specific technical solutions of the present application are as follows:

[0005] A green silicon nitride ceramic material, the raw material composition of which is: 78-95wt% of silicon nitride, 4-14wt% of sintering aid, 1-8wt% of coloring agent Pr6O 11 , the dispersant is 0.5%-5% of the total mass of silicon nitride powder, coloring agent and sintering aid; the binder content is 0.5%-8% of the total mass of silicon nitride, coloring agent and sintering aid, and the plasticizer content is 0.5%-6% of the total mass of silicon nitride powder, coloring agent and sintering aid.

[0006] The density of the green silicon nitride ceramic material is 3.14-3.22 g / cm 3 , the Vickers hardness is 14-15.5 GPa, the bending strength is 850-960 MPa, the thermal conductivity is >83.28 W / (m·K), and the dielectric constant is <7.8 F / m.

[0007] The dispersant is one or more of glycerol trioleate, glycerol monooleate, tributyl citrate.

[0008] The sintering aid is a mixture of a first sintering aid and a second sintering aid, the first sintering aid is one or more of MgO, Al2O3, AlN, CaO, TiO2, and the second sintering aid is one or more of La2O3, Y2O3, Yb2O3.

[0009] Preferably, the mass ratio of the first sintering aid to the second sintering aid is 1-1.6.

[0010] The binder is one or more of polyvinyl butyral, polyethylene glycol, polymethyl methacrylate, and paraffin wax.

[0011] The plasticizer is one or more of ethylene glycol, dibutyl phthalate, and dioctyl phthalate.

[0012] A preparation method of a green silicon nitride ceramic material, comprising the following steps:

[0013] Step 1: prepare the following raw materials, silicon nitride 78-95wt%, sintering aid 4-14wt%, coloring agent Pr6O 11 is 1-8wt%, the dispersant is 0.5%-5% of the total mass of the silicon nitride powder, the coloring agent, and the sintering aid; the binder content is 0.5%-8% of the total mass of the silicon nitride, the coloring agent, and the sintering aid, and the plasticizer content is 0.5%-6% of the total mass of the silicon nitride powder, the coloring agent, and the sintering aid;

[0014] Step 2: mix the raw materials in step 1 with anhydrous ethanol at a solid-liquid ratio of 1:1.5, and grind in a ball mill to obtain a uniform slurry, preferably, the grinding speed is 100-500 r / min; the grinding time is 6-20 h;

[0015] Step 3: sieve the slurry obtained in step 2 after vacuum degassing, shape to prepare a green body, and dry to obtain a green body, the shaping mode is tape casting, slip casting, injection molding, dry pressing, or isostatic pressing;

[0016] S4: place the green body obtained in step 3 in a glue removal furnace, heat to 455℃ at a rate of 0.5℃ / min in a dry air atmosphere, and keep for 3h, preferably, the green body glue removal process parameters are: glue removal temperature 350-800℃; glue removal time 45-60h; glue removal atmosphere is nitrogen, air, and nitrogen-air mixed gas;

[0017] S5: the green body after the glue is discharged is loaded into a BN crucible, placed in a sintering furnace, nitrogen is introduced, sintered at 1850 DEG C, 2MP conditions for 2h, furnace cooling to room temperature, to obtain the final product.

[0018] The filler powder in the crucible in S5 is at least three of Si3N4 powder, BN powder, MgO powder, Pr6O 11 powder, C powder.

[0019] Preferably, the filler powder is composed of Si3N4 powder, BN powder, MgO powder and Pr6O 11 powder, the mass ratio of Si3N4 powder: BN powder: MgO powder: Pr6O 11 powder is 7:5:3:2.

[0020] A communication battery back plate made of the aforementioned green silicon nitride ceramic material, the thickness of the communication battery back plate can be 0.25mm-0.60mm, realizing the light weight of electronic devices.

[0021] Further, the density of the communication battery back plate is 3.14-3.22 g / cm 3 , the Vickers hardness is 14-15.5GPa, the bending strength is 850-960 MPa, the thermal conductivity is >83.28 W / (m·K), and the dielectric constant is <7.8F / m.

[0022] The application is based on Pr6O 11 As a green colorant, at 1800 DEG C high temperature conditions, its Pr 3+ and Pr 4+ can be quickly and reversibly converted to realize coexistence of valence state, the coloring ability of Pr 3+ decomposition is significantly improved, which can realize the coloring sintering of green silicon nitride. 3+ At the same time, as a filler powder, it can effectively inhibit the volatilization of Pr 11 , realize the color consolidation of green silicon nitride. The dual synergistic effect of Pr6O 11The proportion of the added amount as a green colorant and the proportion as a filler powder are combined with the optimized sintering process to realize gradient coloring and performance regulation of the green silicon nitride ceramic. The green silicon nitride ceramic as the communication battery back plate material has reasonable cost, simple process, excellent mechanical properties, thermal properties and good electromagnetic shielding characteristics, is resistant to falling and wear, easy to dissipate heat, light in weight and good in signal transmission effect, and fully meets the performance needs of the silicon nitride as the communication battery back plate. The green silicon nitride makes the color more bright and beautiful, further meets the aesthetic pursuit of the public users, and synchronizes the needs of technology and life. Therefore, the green silicon nitride ceramic material proposed in the application is a new type of communication battery back plate preferred material with great potential. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The XRD pattern of the green silicon nitride ceramic prepared in Example 2 of the application;

[0024] Figure 2 The polished surface optical image of the green silicon nitride ceramic prepared in Example 2 of the application;

[0025] Figure 3 The SEM image of the green silicon nitride ceramic prepared in Example 2 of the application;

[0026] Figure 4 The EDS image of the green silicon nitride ceramic prepared in Example 2 of the application. DETAILED DESCRIPTION

[0027] The application is further described below through specific embodiments, and it should be understood that the following embodiments are only used to illustrate the application, but not to limit the application. The preparation method of the green silicon nitride ceramic is exemplarily described below.

[0028] In the following examples, the raw materials are all selected from industrial grade purity (≥99.9%), and the particle size of the alpha-silicon nitride powder is controlled to be 0.8 μm (in the preferred range of 0.5~1 μm).

[0029] In the application, the density of the green silicon nitride ceramic communication battery back plate material is determined by the Archimedes drainage method. The Vickers hardness of the green silicon nitride ceramic communication battery back plate material is determined by using a Vickers hardness tester (load 5 kg, pressure retention 10 s). The bending strength of the green silicon nitride ceramic communication battery back plate material is determined by a universal material testing machine (three-point bending method, span 20 mm, loading rate 10 mm / min). The thermal conductivity of the green silicon nitride ceramic communication battery back plate material is calculated by the laser flash method (test temperature 25℃). The dielectric constant of the green silicon nitride ceramic communication battery back plate material is determined by using a dielectric constant tester (frequency 1 MHz).

[0030] The theoretical color of the green silicon nitride ceramic communication battery backboard material was determined by using an X-Rite Ci62 spectrophotometer. (L represents lightness, a positive value represents red, a negative value represents green, b positive value represents yellow, and b negative value represents blue. The green characteristic is determined by a value ≤-2.0).

[0031] The following further examples are used to illustrate the present application in detail. It should also be understood that the following examples are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application are within the scope of protection of the present application. The specific process parameters in the following examples are only one example in the appropriate range, i.e. those skilled in the art can select within the appropriate range according to the description herein, and are not limited to the specific values in the following examples.

[0032] Example 1

[0033] A green silicon nitride ceramic communication battery backboard material and a preparation method thereof, comprising the following steps:

[0034] S1: weighing 94 g of α-silicon nitride powder, 4 g of sintering aid (MgO+Al2O3+Y2O3), 2 g of Pr6O 11 coloring agent (±0.1%); meanwhile, weighing 1.92 g of dispersant GTO, 2.88 g of binder PVB, and 1.92 g of plasticizer DBP;

[0035] S2: mixing the above raw materials with anhydrous ethanol (solid-liquid ratio 1:1.5) and placing in a ball mill for grinding at a speed of 300 r / min for 12 h to obtain a uniform slurry;

[0036] S3: after vacuum deaeration, the slurry is sieved through a 200 mesh sieve, and a green body is prepared by flow casting with a scraper gap of 0.5 mm, and dried at 60°C for 2 h to obtain a green body with a thickness of about 0.4 mm; S4: placing the green body in a glue removal furnace, and heating to 455°C at a rate of 0.5°C / min under a dry air atmosphere, and maintaining for 3 h;

[0037] S5: loading the glue-removed green body into a BN crucible, filling the crucible with filler powder in a ratio of 7:5:3:2 (7 g of Si3N4 powder, 5 g of BN powder, 3 g of MgO powder, and 2 g of Pr6O 11 powder), and placing it in a gas pressure sintering furnace, and introducing nitrogen, and sintering at 1850°C and 2 MPa for 2 h, and cooling to room temperature in the furnace to obtain a green silicon nitride ceramic material. The density of the obtained green silicon nitride ceramic material is 3.16±0.1 g / cm 3; Vickers hardness of 14.8±0.3 GPa; bending strength of 900±15 MPa; thermal conductivity of 84.55±0.16 W / (m·K); dielectric constant of 7.6±0.12 F / m; color value of L*=78.3±0.2, a*=-2.1±0.1, b*=1.8±0.1 (light yellow-green, green color characteristics weak).

[0038] Example 2

[0039] A green silicon nitride ceramic communication battery backboard material and a preparation method thereof, comprising the following steps:

[0040] S1: weigh 93g of α-silicon nitride powder, 4g of sintering aid (MgO+Al2O3+Y2O3), 3g of Pr6O 11 coloring agent (±0.1%); meanwhile, weigh 1.92g of dispersant GTO, 2.88g of binder PVB, and 1.92g of plasticizer DBP;

[0041] S2: mix the above raw materials with anhydrous ethanol (solid-liquid ratio 1:1.5), and place in a ball mill for grinding at a speed of 400r / min for 12h to obtain a uniform slurry;

[0042] S3: after vacuum deaeration, the slurry is sieved through a 200 mesh sieve, and a green body is prepared by flow casting with a scraper gap of 0.5mm, and dried at 60℃ for 2h to obtain a green body with a thickness of about 0.4mm; S4: place the green body in a glue removal furnace, and heat to 455℃ at a rate of 0.5℃ / min under a dry air atmosphere, and keep for 3h;

[0043] S5: load the glue-removed green body into a BN crucible, fill the crucible with filler powder in a ratio of 7:5:3:2 (7g of Si3N4 powder, 5g of BN powder, 3g of MgO powder, and 2g of Pr6O 11 powder), and place it in a gas pressure sintering furnace, and introduce nitrogen, and sinter at 1850℃ and 2MP for 2h, and cool to room temperature in the furnace to obtain a green silicon nitride ceramic material. The green silicon nitride ceramic material has a density of 3.21±0.05 g / cm 3 ; Vickers hardness of 15.1±0.25 GPa; bending strength of 950±10 MPa; thermal conductivity of 85.12±0.10 W / (m·K); dielectric constant of 7.25±0.05 F / m; color value of L*=76.9±0.2, a*=-3.5±0.1, b*=1.5±0.1 (bright green, good green uniformity). Example 3

[0044] A green silicon nitride ceramic communication battery backboard material and a preparation method thereof, comprising the following steps:

[0045] S1: take 92 g of α-silicon nitride powder, 3 g of sintering aid (MgO + Al2O3 + Y2O3), 5 g of Pr6O 11 coloring agent (±0.1%); meanwhile, take 1.92 g of dispersant GTO, 2.88 g of binder PVB, and 1.92 g of plasticizer DBP;

[0046] S2: mix the above raw materials with anhydrous ethanol (solid-liquid ratio 1:1.5), place in a ball mill, and grind at a speed of 400 r / min for 12 h to obtain a uniform slurry;

[0047] S3: after vacuum degassing and bubble removal, pass the slurry through a 200 mesh sieve, use a casting forming method to prepare a green body, the scraper gap is 0.5 mm, and dry at 60°C for 2 h to obtain a green body thickness of about 0.4 mm; S4: place the green body in a glue removal oven, heat to 455°C at a rate of 0.5°C / min in a dry air atmosphere, and keep for 3 h;

[0048] S5: load the glue-removed green body into a BN crucible, fill the crucible with filler powder in a ratio of 7:5:3:2 (7 g of Si3N4 powder, 5 g of BN powder, 3 g of MgO powder, and 2 g of Pr6O 11 powder), place it in a gas pressure sintering furnace, introduce nitrogen, sinter at 1850°C and 2 MPa for 2 h, and cool to room temperature in the furnace to obtain a green silicon nitride ceramic material. The green silicon nitride ceramic material obtained has a density of 3.21±0.1 g / cm 3 , a Vickers hardness of 15.2±0.25 GPa, a bending strength of 950±10 MPa, a thermal conductivity of 85.37±0.15 W / (m·K), a dielectric constant of 7.2±0.05 F / m, and a chroma value of L*=75.6±0.2, a*= -3.8±0.1, and b*=1.2±0.1 (bright and deep green, good green uniformity). Example 4

[0049] A green silicon nitride ceramic communication battery back plate material and a preparation method thereof, comprising the following steps:

[0050] S1: take 88 g of α-silicon nitride powder, 5 g of sintering aid (MgO + Al2O3 + Y2O3), 7 g of Pr6O 11 coloring agent (±0.1%); meanwhile, take 1.92 g of dispersant GTO, 2.88 g of binder PVB, and 1.92 g of plasticizer DBP;

[0051] S2: mix the above raw materials with anhydrous ethanol (solid-liquid ratio 1:1.5), place in a ball mill, and grind at a speed of 450 r / min for 18 h to obtain a uniform slurry;

[0052] S3: After vacuum degassing and defoaming, the slurry was sieved through a 200 mesh sieve, and a green body was prepared by tape casting with a doctor blade gap of 0.5 mm. The green body was dried at 60°C for 2 h, and the thickness of the green body was about 0.4 mm; S4: The green body was placed in a debinding furnace and heated to 455°C at a rate of 0.5°C / min under a dry air atmosphere, and held for 3 h;

[0053] S5: The debound green body was loaded into a BN crucible, and the filler powder was mixed in a ratio of 7:5:3:2 (7 g of Si3N4 powder, 5 g of BN powder, 3 g of MgO powder, and 2 g of Pr6O 11 powder) and placed in a gas pressure sintering furnace. Nitrogen was introduced, and the sample was sintered at 1850°C and 2 MPa for 2 h. The furnace was cooled to room temperature, and a green silicon nitride ceramic material was obtained. The density of the green silicon nitride ceramic material was 3.20±0.1 g / cm 3 ; the Vickers hardness was 15.1±0.2 GPa; the bending strength was 910±30 MPa; the thermal conductivity was 85.22±0.10 W / (m·K); the dielectric constant was 7.18±0.05 F / m; and the color value was L*=73.8±0.2, a*=-4.2±0.1, and b*=1.0±0.1 (dark green, with good green uniformity).

[0054] Example 5

[0055] A green silicon nitride ceramic communication battery backsheet material and a preparation method thereof, comprising the following steps:

[0056] S1: 87 g of α-silicon nitride powder, 5 g of sintering aid (MgO+Al2O3+Y2O3), and 8 g of Pr6O 11 coloring agent (±0.1%); 1.92 g of dispersant GTO, 2.88 g of binder PVB, and 1.92 g of plasticizer DBP were also weighed;

[0057] S2: The above raw materials were mixed with anhydrous ethanol (solid-liquid ratio 1:1.5) and placed in a ball mill for grinding at a speed of 450 r / min for 18 h to obtain a uniform slurry;

[0058] S3: After vacuum degassing and defoaming, the slurry was sieved through a 200 mesh sieve, and a green body was prepared by tape casting with a doctor blade gap of 0.5 mm. The green body was dried at 60°C for 2 h, and the thickness of the green body was about 0.4 mm; S4: The green body was placed in a debinding furnace and heated to 485°C at a rate of 0.3°C / min under a dry air atmosphere, and held for 3 h;

[0059] S5: Put the green body after degreasing and glue removal into a BN crucible, and fill the filler powder in the crucible according to a ratio of 7:5:3:2 (7 g of Si3N4 powder, 5 g of BN powder, 3 g of MgO powder, and 2 g of Pr6O 11 powder), place it in a gas pressure sintering furnace, introduce nitrogen, sinter at 1850 ℃ and 2 MPa for 2 h, and cool to room temperature with the furnace to obtain a green silicon nitride ceramic material. The density of the obtained green silicon nitride ceramic material is 3.19±0.1 g / cm 3 ; the Vickers hardness is 15.0±0.2 GPa; the bending strength is 880±25 MPa; the thermal conductivity is 85.35±0.13 W / (m·K); the dielectric constant is 7.28±0.05 F / m; and the chroma value is L*=72.1±0.2, a*=-5.2±0.1, and b*=0.9±0.1 (dark green, with discoloration phenomenon at the edge part).

[0060] Example 6

[0061] A green silicon nitride ceramic communication battery backboard material and a preparation method thereof, comprising the following steps:

[0062] S0: Pr6O 11 coloring agent content (5%) + Pr6O 11 filler powder high ratio (7:5:3:4)

[0063] S1: The coloring agent and the auxiliary agent system are the same as in Example 3

[0064] S2: The wet grinding process is the same as in Example 3

[0065] S3: The tape casting process is the same as in Example 3 S4: The degreasing and glue removal process is the same as in Example 3

[0066] S5: Put the green body after degreasing and glue removal into a BN crucible, and fill the filler powder in the crucible according to a ratio of 7:5:3:4 (7 g of Si3N4 powder, 5 g of BN powder, 3 g of MgO powder, and 4 g of Pr6O 11 powder), place it in a gas pressure sintering furnace, introduce nitrogen, sinter at 1850 ℃ and 2 MPa for 2 h, and cool to room temperature with the furnace to obtain a green silicon nitride ceramic material. The density of the obtained green silicon nitride ceramic material is 3.20±0.1 g / cm 3 ; the Vickers hardness is 15.13±0.05 GPa; the bending strength is 930±15 MPa; the thermal conductivity is 84.22±0.13 W / (m·K); the dielectric constant is 7.32 F / m; and the chroma value is L*=74.8±0.2, a*=-4.0±0.1, and b*=1.0±0.1 (green saturation is slightly higher than that in Example 3, and no color change caused by Pr 3+ volatilization).

[0067] Comparative Example 1

[0068] A green silicon nitride ceramic communication battery backboard material and a preparation method thereof, comprising the following steps:

[0069] S0: medium Pr6O 11 Colorant content (5%) + Pr6O 11 Filler powder low ratio (7:5:3:1)

[0070] S1: colorant and auxiliary agent system same as example 3

[0071] S2: wet grinding process same as example 3

[0072] S3: flow forming process same as example 3 S4: degreasing and glue removal process same as example 3

[0073] S5: the green body after glue removal is loaded into a BN crucible, the filler powder in the crucible is filled according to a ratio of 7:5:3:1 (7g Si3N4 powder, 5g BN powder, 3g MgO powder, 1g Pr6O 11 powder), and it is placed in a gas pressure sintering furnace, nitrogen is introduced, sintering is carried out at 1850℃, 2MP for 2h, the furnace is cooled to room temperature, and a green silicon nitride ceramic material is obtained. The density of the obtained green silicon nitride ceramic material is 3.20±0.15 g / cm 3 ; the Vickers hardness is 15.2±0.12 GPa; the bending strength is 915±18 MPa; the thermal conductivity is 84.07±0.11 W / (m·K); the dielectric constant is 7.54 F / m; the chroma value is L*=76.2±0.2, a*=-3.5±0.1, b*=1.5±0.1 (the green saturation is lower than that of example 3, and there are shallow spots locally, which is speculated to be Pr 3+ Comparative Example 2

[0074] A green silicon nitride ceramic communication battery backboard material and a preparation method thereof, comprising the following steps:

[0075] S0: medium Pr6O 11 Colorant content (5%) + Pr6O 11 Filler powder (7:5:3:0)

[0076] S1: colorant and auxiliary agent system same as example 3

[0077] S2: wet grinding process same as example 3

[0078] S3: flow forming process same as example 3 S4: degreasing and glue removal process same as example 3

[0079] S5: The green body after degreasing and glue removal was loaded into a BN crucible, and the filler powder in the crucible was proportioned at 7:5:3:1 (7 g of Si3N4 powder, 5 g of BN powder, 3 g of MgO powder, and 1 g of Pr6O 11 powder) and placed in a gas pressure sintering furnace, nitrogen was introduced, sintered at 1850℃, 2MP for 2h, and cooled to room temperature with the furnace, to obtain green silicon nitride ceramic material. The density of the obtained green silicon nitride ceramic material was 3.21±0.18 g / cm 3 ; the Vickers hardness was 15.2±0.14 GPa; the bending strength was 918±18 MPa; the thermal conductivity was 84.97±0.1 W / (m·K); the dielectric constant was 7.64±0.1 F / m; and the chroma value was L*=79.5±0.2, a*=-2.5±0.1, and b*=2.2±0.1 (green color significantly lightened, edges showed light yellow, Pr³+ volatilization was serious, and it did not meet the green characteristic requirements).

[0080] Comparative Example 3

[0081] A green silicon nitride ceramic communication battery back plate material and a preparation method thereof, comprising the following steps:

[0082] S0: 5% content of Tb4O7 colorant + standard Tb4O7 filler powder proportioning (7:5:3:2)

[0083] S1: 88 g of α-silicon nitride powder, 5 g of sintering aid (MgO+Al2O3+Y2O3), and 5 g of Tb4O7 colorant (±0.1%) were weighed; 1.92 g of dispersant GTO, 2.88 g of binder PVB, and 1.92 g of plasticizer DBP were weighed at the same time;

[0084] S2: wet grinding process same as Example 3

[0085] S3: flow casting process same as Example 3 S4: degreasing and glue removal process same as Example 3

[0086] S5: The green body after degreasing and glue removal was loaded into a BN crucible, and the filler powder in the crucible was proportioned at 7:5:3:2 (7 g of Si3N4 powder, 5 g of BN powder, 3 g of MgO powder, and 2 g of Tb4O7 powder), and placed in a gas pressure sintering furnace, nitrogen was introduced, sintered at 1850℃, 2MP for 2h, and cooled to room temperature with the furnace, to obtain green silicon nitride ceramic material. The density of the obtained green silicon nitride ceramic material was 3.12±0.1 g / cm 3; the Vickers hardness is 13.1±0.2 GPa; the bending strength is 800±35 MPa; the thermal conductivity is 73.86±0.10 W / (m·K); the dielectric constant is 7.3±0.1 F / m; the chroma value is L*=83.2±0.2, a*=-2.2±0.1, b*=3.0±0.1 (white and green color spots, light color and uneven distribution, and the valence state of the Tb4O7 colorant is unstable in liquid phase sintering).

[0087] Comparative Example 4

[0088] A green silicon nitride ceramic communication battery back plate material and a preparation method thereof, comprising the following steps:

[0089] S1: weigh 88g of α-silicon nitride powder, 5g of sintering aid (MgO+Al2O3+Y2O3), 5g of Eu2O3 and Dy2O3 colorant (±0.1%); meanwhile, weigh 1.92g of dispersant GTO, 2.88g of binder PVB, and 1.92g of plasticizer DBP;

[0090] S2: the wet grinding process is the same as that in Example 3

[0091] S3: the flow casting process is the same as that in Example 3 S4: the debinding and glue removal process is the same as that in Example 3

[0092] S5: the green body after glue removal is loaded into a BN crucible, filler powder is filled in the crucible in a ratio of 7:5:3:2 (7g of Si3N4 powder, 5g of BN powder, 3g of MgO powder, and 2g of Eu2O3 and Dy2O3 powder), and the green body is placed in a gas pressure sintering furnace, nitrogen is introduced, sintering is carried out at 1850℃ and 2MP for 2h, and the furnace is cooled to room temperature, to obtain a green silicon nitride ceramic material. The density of the obtained green silicon nitride ceramic material is 3.0±0.1 g / cm 3 ; the Vickers hardness is 13.4±0.1 GPa; the bending strength is 790±20 MPa; the thermal conductivity is 69.55±0.10 W / (m·K); the dielectric constant is 8.0±0.05 F / m; the chroma value is L*=78.2±0.2, a*=-8.8±0.1, b*=23.0±0.1 (yellow-green color, and the mixed effect of Eu2O3 and Dy2O3 colorants). The performance parameters of the products prepared in Examples 1-6 and Comparative Examples 1-4 are shown in Table 1. As shown in Table 1, by means of the dual effects of the “colorant+filler powder”, the gradient coloring and performance regulation of the green silicon nitride ceramic can be realized. 11 When the content of the colorant is 3wt%-7wt%, the filler powder is Si3N4 powder: BN powder: MgO powder: Pr6O 11 and the content of the colorant is 3wt%-7wt%, the filler powder is Si3N4 powder: BN powder: MgO powder: Pr6O 11When the mass ratio is 7:5:3: (2~4), the final product can simultaneously meet the core requirements of "bright and uniform dark green color (a*≤-3.5), high bending strength (≥930 MPa), and high thermal conductivity (≥85 W / (m·K))" of the communication battery back plate, and has the potential for industrial application with stable process and controllable cost.

[0093] Although the above embodiments make a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and cannot be understood as a limitation on the protection scope of the present application. Some non-essential improvements and adjustments made by the person skilled in the art according to the above content of the present application all belong to the protection scope of the present application.

[0094] Table 1 Performance parameters of green silicon nitride ceramics prepared in Examples 1~6 and Comparative Examples 1-4

[0095]

Claims

1. A green silicon nitride ceramic material, characterized in that, Its raw material composition is: 78-95 wt% silicon nitride, 4-14 wt% sintering aid, and Pr6O colorant. 11 The content of the binder is 1-8 wt%, the dispersant is 0.5%-5% of the total mass of silicon nitride powder, colorant and sintering aid; the binder content is 0.5%-8% of the total mass of silicon nitride powder, colorant and sintering aid; and the plasticizer content is 0.5%-6% of the total mass of silicon nitride powder, colorant and sintering aid.

2. The green silicon nitride ceramic material according to claim 1, characterized in that, Its density is 3.14–3.22 g / cm³. 3 It has a Vickers hardness of 14–15.5 GPa, a flexural strength of 850–960 MPa, a thermal conductivity of >83.28 W / (m·K), and a dielectric constant of <7.8 F / m.

3. The green silicon nitride ceramic material according to claim 1, characterized in that, The dispersant is one or more of trioleic acid glyceride, monooleic acid glyceride, and tributyl citrate.

4. The green silicon nitride ceramic material according to claim 1, characterized in that, The sintering aid is a mixture of a first sintering aid and a second sintering aid. The first sintering aid is one or more of MgO, Al2O3, AlN, CaO, and TiO2; the second sintering aid is one or more of La2O3, Y2O3, and Yb2O3.

5. The green silicon nitride ceramic material according to claim 4, characterized in that, The mass ratio of the first sintering aid to the second sintering aid is 1-1.

6.

6. The green silicon nitride ceramic material according to claim 1, characterized in that, The adhesive is one or more of polyvinyl butyral, polyethylene glycol, polymethyl methacrylate, and paraffin.

7. The green silicon nitride ceramic material according to claim 1, characterized in that, The plasticizer is one or more of ethylene glycol, dibutyl phthalate, and dioctyl phthalate.

8. A method for preparing a green silicon nitride ceramic material, characterized in that, Includes the following steps: Step 1: Prepare the following raw materials: 78-95 wt% silicon nitride, 4-14 wt% sintering aid, and Pr6O colorant. 11 The content of the binder is 1-8 wt%, and the content of the dispersant is 0.5%-5% of the total mass of silicon nitride powder, colorant, and sintering aid; the content of the binder is 0.5%-8% of the total mass of silicon nitride powder, colorant, and sintering aid, and the content of the plasticizer is 0.5%-6% of the total mass of silicon nitride powder, colorant, and sintering aid. Step 2: Mix the raw materials from Step 1 with anhydrous ethanol at a solid-liquid ratio of 1:1.5, and grind them in a ball mill to obtain a uniform slurry; Step 3: The slurry obtained in Step 2 is vacuum defoamed, sieved, shaped into green bodies, and dried to obtain green bodies; S4: Place the green body obtained in step 3 in a debinding furnace, and heat it to 455℃ at a rate of 0.5℃ / min under a dry air atmosphere, and hold it for 3 hours; S5: After debinding, the green body is placed into a BN crucible, placed in a sintering furnace, and nitrogen is introduced. It is then sintered at 1850℃ and 2MP for 2 hours. After cooling to room temperature in the furnace, the final product is obtained.

9. The method for preparing green silicon nitride ceramic material according to claim 8, characterized in that, The filler powder in the crucible in S5 is Si3N4 powder, BN powder, MgO powder, and Pr6O. 11 At least three of the following: powder, C powder.

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