Calcium bismuth titanate-based piezoelectric ceramic as well as preparation method and application thereof

Abstract

The invention discloses a calcium bismuth titanate-based piezoelectric ceramic and a preparation method and application thereof.The preparation method of the calcium bismuth titanate-based piezoelectric ceramic comprises the steps that a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source, an Nb source and a Cr source are mixed to obtain a mixture, the mixture is evenly mixed and pre-sintered at 750-900 DEG C for 2-4 h, and a pre-sintered material is obtained; uniformly mixing the pre-sintered material, granulating, carrying out vacuum packaging, and carrying out warm isostatic pressing to obtain a green body column; carrying out glue removal treatment on the green body column, and carrying out first sintering at 1000-1300 DEG C to obtain a ceramic material; the ceramic material is sequentially subjected to high-temperature silver paste coating, secondary sintering and silicone oil medium-high-voltage polarization, and the calcium bismuth titanate based piezoelectric ceramic is obtained. According to the calcium bismuth titanate based piezoelectric ceramic, the Curie temperature reaches up to 786 DEG C, meanwhile, the piezoelectric constant is 24 pC / N, the dielectric loss is 0.12%, and the resistivity at 600 DEG C is 7.5 * 10 < 6 > omega.cm.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric ceramics, and in particular relates to a calcium bismuth titanate-based piezoelectric ceramic and a preparation method and application thereof. Background Art

[0002] High temperature acceleration sensors can monitor some devices in the fields of aerospace, geological survey, petrochemical, automobile engines, etc. in real time at high temperatures. Piezoelectric materials, especially high temperature piezoelectric ceramic materials, must be used to prepare high temperature acceleration sensors.

[0003] At present, the most widely used high-temperature piezoelectric ceramic material is lead zirconate titanate (PZT)-based piezoelectric ceramic material, but its Curie temperature is too low, only between 250 and 380°C, and the safe operating temperature is limited to 1 / 2 of the Curie temperature. Therefore, this type of ceramic can no longer meet the requirements of current high-tech development.

[0004] Calcium bismuth titanate (CaBi4Ti4O 15 ) based ceramic materials are also often used in high temperature acceleration sensors, with a Curie temperature of up to 790°C and a piezoelectric constant of d 33 About 7pC / N. In practical applications, its piezoelectric constant is too low and the temperature drift of the piezoelectric constant (i.e. the change of the piezoelectric constant with temperature) is also too large. 15 While increasing the Curie temperature of base ceramic materials, improving the piezoelectric constant, increasing the resistivity and enhancing the thermal stability are key issues. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing calcium bismuth titanate-based piezoelectric ceramics. The preparation method first prepares calcium bismuth titanate (CaBi4Ti4O 15 ) A-site doping in base ceramic materials (NaCe) 5+ Composite ions (Na and Ce simultaneously replace the A position in the crystal), B position doping (Co 1 / 2 Nb 1 / 2 ) 4+ Composite ions (Co and Nb simultaneously replace the B position in the crystal), on this basis, Cr2O3 is doped for modification (not participating in the substitution) to obtain bismuth calcium titanate-based piezoelectric ceramics.

[0006] Another object of the present invention is to provide bismuth calcium titanate-based piezoelectric ceramics obtained by the above preparation method.

[0007] Another object of the present invention is to provide an application of the above-mentioned bismuth calcium titanate-based piezoelectric ceramic in an acceleration sensor.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A method for preparing bismuth calcium titanate-based piezoelectric ceramics comprises the following steps: Step 1, mixing a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source, a Nb source and a Cr source to obtain a mixture, mixing the mixture evenly, and pre-sintering at 750-900° C. for 2-4 hours to obtain a pre-sintered material, wherein, by amount of substance, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is (0.88-0.98): (0.008-0.048): (0.008-0.048): 4: (3.88-3.98): (0.01-0.06): (0.01-0.06): (0.02-0.08); In step 1, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is preferably (0.93-0.95): (0.02-0.03): (0.02-0.03): 4: (3.93-3.95): (0.025-0.035): (0.025-0.035): 0.02, calculated by amount.

[0010] In step 1, the Ca source is CaCO3, the Na source is Na2CO3, the Ce source is CeO2, the Bi source is Bi2O3, the Ti source is TiO2, the Co source is Co2O3, the Nb source is Nb2O5, and the Cr source is Cr2O3.

[0011] In step 1, the pre-sintering is performed in an air environment.

[0012] Step 2, mixing the pre-sintered materials uniformly, granulating, vacuum packaging, and warm isostatic pressing to obtain a green column; In step 2, the granulation uses a binder, and the ratio of the binder to the pre-sintered material is (2-5):1 by weight.

[0013] In the above technical solution, the adhesive is a polyvinyl alcohol (PVA) aqueous solution, and the polyvinyl alcohol (PVA) aqueous solution is a mixture of polyvinyl alcohol (PVA) and water. Calculated by mass, the ratio of water to polyvinyl alcohol in the polyvinyl alcohol (PVA) aqueous solution is (15~20):1.

[0014] In step 2, the vacuum packaging includes: column packaging at a pressure of 2-4 MPa.

[0015] In step 2, the pressure of the warm isostatic pressing is 30-50 MPa, the holding time of the warm isostatic pressing is 10-20 s, and the temperature of the warm isostatic pressing is 25-40°C.

[0016] In the above technical solution, the pressure increase rate of the warm isostatic pressing is 2~3MPa / s.

[0017] In step 1 and step 2, the mixing is performed uniformly by ball milling, the ball milling is wet milling, and the medium of wet milling is anhydrous ethanol.

[0018] In the above technical solution, the ball-to-material ratio of the ball mill is (3-5):1 by mass.

[0019] In the above technical solution, the wet grinding is followed by drying, the drying temperature is 70-80° C., and the drying time is 7-8 hours.

[0020] In the above technical solution, the rotation speed of the ball mill is 300-400 r / min, and the ball milling time is 8-12 h.

[0021] Step 3, debinding the green column, and performing a first sintering at 1000-1300° C. to obtain a ceramic material, wherein the first sintering time is 3-5 hours; In step 3, the temperature of the debinding treatment is 550-650° C., and the time of the debinding treatment is 0.5-2 h.

[0022] In the above technical solution, the heating rate to 550~650℃ is 3~5℃ / min.

[0023] In step 3, the heating rate to 1000-1300°C is 3-5°C / min.

[0024] In step 3, the first sintering is performed in an air environment.

[0025] Step 4, the ceramic material is coated with high-temperature silver paste (electrode), sintered for the second time (electrode sintering), and polarized at high voltage in silicone oil to obtain bismuth calcium titanate-based piezoelectric ceramics.

[0026] In step 4, the second sintering includes: keeping the temperature at 800-850° C. for 10-40 minutes in an air environment.

[0027] In step 4, the high voltage polarization in silicone oil includes: polarizing in silicone oil at 150-200° C. with a polarization field strength of 10-12 kV / mm for 30-40 minutes.

[0028] The calcium bismuth titanate-based piezoelectric ceramics obtained by the above preparation method.

[0029] Application of the above-mentioned bismuth calcium titanate-based piezoelectric ceramics in acceleration sensors.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. The calcium bismuth titanate-based piezoelectric ceramics of the present invention are based on composite ions (NaCe) 5+ Replace Ca element, composite ion (Co 1 / 2Nb 1 / 2 ) 4+ Replace Ti element, compared with CaBi4Ti4O 15 The present invention improves the piezoelectric constant and the resistivity at high temperature while ensuring that the Curie temperature does not drop, and reduces the dielectric loss. The bismuth calcium titanate-based piezoelectric ceramic of the present invention has a Curie temperature of up to 786°C, a piezoelectric constant of 24pC / N (room temperature), a dielectric loss of 0.12% (room temperature), and a resistivity of 7.5×10 6 Ω·cm; 2. The bismuth calcium titanate-based piezoelectric ceramics of the present invention have a piezoelectric constant temperature drift of less than 5.6% at room temperature to 650°C, and can operate stably for a long time at 650°C; 3. The dielectric loss of the calcium bismuth titanate-based piezoelectric ceramic of the present invention changes little with temperature at room temperature to 600°C; 4. The resistivity of the calcium bismuth titanate-based piezoelectric ceramics of the present invention can reach 7.5×10 6 Ω·cm, compared with CaBi4Ti4O 15 Based on ceramic materials, the temperature is improved by two orders of magnitude at the same temperature, and has great application prospects in the field of high-temperature devices; 5. The preparation method of the present invention is simple, low-cost and suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 XRD diffraction patterns of calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6; Figure 2 The scanning electron microscope images (SEM) of the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 2 to 5 are shown in Figures 2 to 5, wherein (a) to (d) are the SEM images of the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 2 to 5, respectively; Figure 3 The graph showing the change of dielectric loss of calcium bismuth titanate-based piezoelectric ceramics obtained in Examples 1 to 6 with temperature; Figure 4 The dielectric loss of the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 varies with temperature; Figure 5 This is a graph showing the change in dielectric constant of the calcium bismuth titanate-based piezoelectric ceramic prepared in Example 3 as a function of temperature; Figure 6 The piezoelectric constant of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 varies with temperature; Figure 7 This is a graph showing the variation of the piezoelectric constant of the piezoelectric ceramic material prepared in Comparative Example 3 with temperature; Figure 8 The piezoelectric constant of the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 varies with temperature; Fig. 9 The resistivity of calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 varies with temperature. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0033] In the following examples, the Ca source is CaCO3, the Na source is Na2CO3, the Ce source is CeO2, the Bi source is Bi2O3, the Ti source is TiO2, the Co source is Co2O3, the Nb source is Nb2O5, and the Cr source is Cr2O3. CaCO3, Na2CO3, CeO2, Bi2O3, TiO2, Co2O3, Nb2O5, and Cr2O3 are all analytically pure.

[0034] High temperature silver paste: Xi'an Hongxingxing Electronic Paste Technology Co., Ltd., model C-1002.

[0035] The following piezoelectric constant, dielectric constant, dielectric loss, and electromechanical coupling coefficient are all obtained by testing at room temperature of 20~25℃ unless otherwise specified.

[0036] Embodiment 1~6

[0037] A method for preparing bismuth calcium titanate-based piezoelectric ceramics comprises the following steps: Step 1, mixing a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source, a Nb source and a Cr source to obtain a mixture, ball milling the mixture at a speed of 300 r / min for 8 hours until the mixture is uniformly mixed (wet milling is adopted for ball milling, and the medium of wet milling is anhydrous ethanol. In this step, the ratio of anhydrous ethanol to the mixture is 4:3 by weight, and the ball-to-material ratio of ball milling is 4:1 by weight), drying at 75° C. for 8 hours, and pre-sintering at 850° C. for 3 hours in an air environment to obtain a pre-sintered material, wherein, in terms of the amount of substance, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is A, and the value of A is shown in Table 1; Step 2, ball milling the pre-sintered material at a speed of 300 r / min for 8 hours until it is uniformly mixed (wet milling is used for ball milling, and the medium for wet milling is anhydrous ethanol. In this step, the ratio of anhydrous ethanol to the pre-sintered material is 4:3 by weight, and the ball-to-material ratio of ball milling is 4:1 by weight), drying at 75°C for 8 hours, granulating, vacuum packaging (using a dry pressing type tablet press to press the column packaging at a pressure of 3 MPa), and hot isostatic pressing at 40°C and a pressure of 40 MPa for 10 seconds (the pressure increase rate of hot isostatic pressing is 3 MPa / s) to obtain a green column with a thickness of 13 mm and a diameter of 10 mm, wherein a binder is used for granulation, and the ratio of the binder to the pre-sintered material is 4:1 by weight, and the binder is a polyvinyl alcohol (PVA) aqueous solution, and the polyvinyl alcohol (PVA) aqueous solution is a mixture of polyvinyl alcohol (PVA) and water, and the ratio of water to polyvinyl alcohol in the polyvinyl alcohol (PVA) aqueous solution is 18:1 by weight; Step 3, heating the green body column to 650°C at a rate of 4°C / min and performing a binder removal treatment at 650°C for 2 hours to remove the binder (which can also make the ceramic material have a certain hardness), and performing a first sintering at 1160°C in an air environment (the heating rate to 1160°C is 4°C / min) to obtain a ceramic material, wherein the first sintering time is 3 hours; Step 4, cut the ceramic material into ceramic sheets with a thickness of 0.6 mm, polish both sides of the ceramic sheets with 600 mesh sandpaper, and after polishing, coat high-temperature silver paste on both sides of the ceramic sheets (electrode), and keep them at 850°C for 20 minutes in an air environment for a second sintering (electrode sintering). After the second sintering, polish and grind off the surface silver oxide on A4 paper, and polarize them at high voltage in silicone oil to obtain bismuth calcium titanate-based piezoelectric ceramics, wherein the high voltage polarization in silicone oil is polarization at a polarization field strength of 11.5 kV / mm in silicone oil at 180°C for 40 minutes.

[0038] Table 1

[0039] Comparative Examples 1 to 6

[0040] A method for preparing a piezoelectric ceramic material is basically the same as that in Example 1, except that: the mixed material, the mixed materials of Comparative Examples 1 to 6 are all obtained by mixing a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source and a Nb source, and the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source and Nb in the Nb source is B, and the B value is shown in Table 2.

[0041] Table 2

[0042] Comparative Examples 7-12

[0043] A method for preparing a piezoelectric ceramic material is basically the same as that in Example 1, except that: the mixed material, the mixed materials of Comparative Examples 7 to 12 are all obtained by mixing a Ca source, a Ce source, a Bi source, a Ti source, a Co source, a Nb source and a Cr source, and the ratio of Ca in the Ca source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is C, and the C value is shown in Table 3.

[0044] Table 3

[0045] The piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 are Ce-doped at the A position. 4+ ions, B-site doping (Co 1 / 2 Nb 1 / 2 ) 4+ Composite ions, on this basis, are doped with Cr2O3 (not participating in substitution).

[0046] Comparative Example 13

[0047] A bismuth calcium titanate-based piezoelectric ceramic material is prepared according to Example 1 of the invention patent with publication number CN 116120054 A.

[0048] The Curie temperatures of the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 1 to 6, the piezoelectric ceramic materials prepared in Comparative Examples 1 to 12, and the bismuth calcium titanate-based piezoelectric ceramic materials prepared in Comparative Example 13 are ( T c ), the piezoelectric constant at room temperature ( d 33 ), resistivity (ρ), room temperature dielectric constant, room temperature dielectric loss (tanδ), and room temperature electromechanical coupling coefficient ( k p ) as shown in Table 4.

[0049] Table 4

[0050] The XRD diffraction patterns of the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 1 to 6 are as follows: Figure 1 As shown, it is shown that the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 1 to 6 all formed a single bismuth calcium titanate structure without generating a second phase. 5+ and (Co 1 / 2 Nb 1 / 2 ) 4+ It has been successfully doped with CaBi4Ti4O 15 middle.

[0051] The SEM scanning electron microscope images of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 2 to 5 are as follows: Figure 2 As shown, the grain boundaries of the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 2 to 5 are clearly visible and densely arranged, indicating that the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 2 to 5 have good density.

[0052] The dielectric loss of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 varies with temperature. Figure 3 As shown ( Figure 3 The vertical axis "loss" represents the dielectric loss, and the temperature change range in the horizontal axis is: room temperature ~ 600 ° C). In the range of room temperature ~ 600 ° C, as the temperature increases, the dielectric loss changes slowly, indicating that the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 1 to 6 have excellent thermal stability and good piezoelectric properties.

[0053] The dielectric loss of the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 varies with temperature. Figure 4 As shown ( Figure 4 The vertical axis "loss" represents the dielectric loss, and the temperature variation range in the horizontal axis is: room temperature ~ 600 ° C). In the range of room temperature ~ 600 ° C, as the temperature increases, the dielectric loss of the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 changes more than the bismuth calcium titanate-based piezoelectric ceramics prepared in Examples 1 to 6, indicating that the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 have poor thermal stability.

[0054] Example 3 The dielectric constant of the prepared calcium bismuth titanate-based piezoelectric ceramics varies with temperature. Figure 5 As shown, there is an obvious mutation at a temperature of 786°C. Before this temperature, the dielectric constant increases slowly with increasing temperature. After reaching 786°C, the dielectric constant increases sharply with increasing temperature. This mutation point is its Curie temperature. The Curie temperature of the bismuth calcium titanate-based piezoelectric ceramics prepared in Example 3 is as high as 786°C.

[0055] The piezoelectric constant of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 varies with temperature. Figure 6 As shown in the figure, within the range of room temperature to 650°C, as the temperature increases, the piezoelectric constant of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 changes little, has excellent thermal stability, and is Figure 6 It can be seen that within the range of room temperature to 650°C, the piezoelectric constant change rate of the calcium bismuth titanate-based piezoelectric ceramic prepared in Example 3 (the best embodiment) is 5.6%. The piezoelectric constant of the piezoelectric ceramic material prepared in Comparative Example 3 changes with temperature as shown in Figure 7 As shown by Figure 7 It can be seen that although the piezoelectric ceramic material prepared in Comparative Example 3 has a high piezoelectric constant, its thermal stability is poor.

[0056] The piezoelectric constants of the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 vary with temperature. Figure 8 As shown, within the range of room temperature to 650°C, as the temperature increases, the piezoelectric ceramic materials prepared in Comparative Examples 7 to 12 change greatly, among which the piezoelectric constant change rate of the piezoelectric ceramic material prepared in Comparative Example 9 within the range of room temperature to 650°C is 11.2%.

[0057] The resistivity of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 varies with temperature. Fig. 9 As shown in Figure 2, the resistivity of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 reached 10 at 600°C. 6 Ω·cm or more, with a very high resistivity. Among them, the resistivity of the calcium bismuth titanate-based piezoelectric ceramic prepared in Example 3 is the highest, reaching 7.5×10 6 Ω·cm, and at 400°C, the resistivity of the calcium bismuth titanate-based piezoelectric ceramics prepared in Examples 1 to 6 is as high as 10 8 Ω·cm or more.

[0058] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for preparing calcium bismuth titanate-based piezoelectric ceramics, characterized in that: The following steps are involved: Step 1, mixing a Ca source, a Na source, a Ce source, a Bi source, a Ti source, a Co source, a Nb source and a Cr source to obtain a mixture, mixing the mixture evenly, and pre-sintering at 750-900° C. for 2-4 hours to obtain a pre-sintered material, wherein, by amount of substance, the ratio of Ca in the Ca source, Na in the Na source, Ce in the Ce source, Bi in the Bi source, Ti in the Ti source, Co in the Co source, Nb in the Nb source and Cr in the Cr source is (0.88-0.98): (0.008-0.048): (0.008-0.048): 4: (3.88-3.98): (0.01-0.06): (0.01-0.06): (0.02-0.08); Step 2, mixing the pre-sintered materials uniformly, granulating, vacuum packaging, and warm isostatic pressing to obtain a green column; Step 3, debinding the green column, and performing a first sintering at 1000-1300° C. to obtain a ceramic material, wherein the first sintering time is 3-5 hours; Step 4: coating the ceramic material with high-temperature silver paste, sintering for a second time, and polarizing it in silicone oil at high voltage to obtain bismuth calcium titanate-based piezoelectric ceramics.

2. The preparation method according to claim 1, characterized in that: In step 2, the granulation uses a binder, and the ratio of the binder to the pre-sintered material is (2-5):1 by weight.

3. The preparation method according to claim 1, characterized in that: In step 2, the vacuum packaging includes: column packaging at a pressure of 2-4 MPa.

4. The preparation method according to claim 1, characterized in that: In step 2, the pressure of the warm isostatic pressing is 30-50 MPa, the holding time of the warm isostatic pressing is 10-20 s, and the temperature of the warm isostatic pressing is 25-40°C.

5. The preparation method according to claim 1, characterized in that: In step 3, the temperature of the debinding treatment is 550-650° C., and the time of the debinding treatment is 0.5-2 h.

6. The preparation method according to claim 1, characterized in that: In step 4, the second sintering includes: keeping the temperature at 800-850° C. for 10-40 minutes in an air environment.

7. The preparation method according to claim 1, characterized in that: In step 4, the high voltage polarization in silicone oil includes: polarizing in silicone oil at 150-200° C. with a polarization field strength of 10-12 kV / mm for 30-40 minutes.

8. The preparation method according to claim 4, characterized in that: The pressure increase rate of the warm isostatic pressing is 2-3 MPa / s.

9. The bismuth calcium titanate-based piezoelectric ceramic obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the bismuth calcium titanate-based piezoelectric ceramic according to claim 9 in an acceleration sensor.

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