Composite ion-doped CBN piezoelectric ceramic material suitable for ultrahigh-temperature service environment and preparation method of composite ion-doped CBN piezoelectric ceramic material

Abstract

The invention belongs to the technical field of piezoelectric ceramics, and discloses a composite ion doped CBN piezoelectric ceramic material suitable for an ultra-high temperature service environment and a preparation method thereof, the structural general formula of the material is Ca (1-x) CexBi2Nb (2-y) (W2 / 3Cr1 / 3) yO9, x is greater than or equal to 0.01 and less than or equal to 0.3, and y is greater than or equal to 0.01 and less than or equal to 0.3. 0.01 < = y < = 0.03; x represents the doping concentration of Ce, and y represents the doping concentration of W and Cr. The composite doped CBN piezoelectric ceramic material provided by the invention has relatively high Curie temperature, relatively high piezoelectric constant and relatively low dielectric loss, can be suitable for a high-temperature environment of 500 DEG C or above, and is stable in performance.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramic technology, and relates to a CBN piezoelectric ceramic, and more particularly to a composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments and its preparation method. Background Technology

[0002] With the advancement of science and technology, large industrial equipment is increasingly being used in high-temperature applications, creating an urgent need for electronic components capable of sensing, actuation, and detonation in high-temperature environments. For example, vibration monitoring of high-temperature components in large power units such as aircraft engines and ship gas turbines requires high-temperature piezoelectric accelerometers; the detonation of strategic weapons penetrating the atmosphere requires high-temperature piezoelectric fuse sensors; and the operation of large high-temperature fatigue life testing machines requires high-temperature piezoelectric transducers. These piezoelectric devices all require a piezoelectric ceramic that can operate at high temperatures as its sensing element. However, the maximum operating temperature of piezoelectric ceramics generally does not exceed 3 / 5 of their Curie temperature. Since these high-temperature piezoelectric devices with special applications need to operate at least continuously above 300°C, and even for short periods above 500°C, traditional PZT series piezoelectric ceramics, due to their Curie temperature limitation (T... C =360 ℃) is no longer applicable, and the Pb element it contains is harmful to the natural environment and human body. Therefore, there is an urgent need to develop a new type of lead-free piezoelectric ceramic with a high Curie temperature as a sensitive material.

[0003] In areas with high Curie temperatures (T) C Among lead-free piezoelectric ceramic material systems (≥500 ℃), bismuth calcium niobate: CaBi₂Nb₂O₉ (CBN) is one of the most studied compounds and also the most representative type of bismuth layered ferroelectric material (BLSF). CBN has a relatively simple structure, with an orthorhombic structure consisting of a bismuth oxide layer (Bi₂O₂). 2+ and (CaNb2O7) 2- It is composed of alternating arrangements according to a certain pattern. CBN has a very high Curie temperature (T). C =940 ℃), and its structural stability is stronger than many other BLSFs. Furthermore, it has a low dielectric constant (ε0.05). r It has the characteristics of low dielectric loss (tanδ < 10%) and high mechanical quality factor (Qm around 3000). However, CBN also has other disadvantages. Due to its limited spontaneous polarization and high coercive field, its piezoelectric coefficient is relatively low (5 pC / N). Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments. By performing composite ion doping on CBN piezoelectric ceramic materials, a piezoelectric ceramic material with high temperature resistance, excellent performance, and stability is obtained.

[0005] Another objective of this invention is to provide a method for preparing the aforementioned composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments.

[0006] The inventive concept of this invention is as follows: Based on CaBi2Nb2O9 (CBN), with Ca sites as A sites and Nb sites as B sites, Ce is doped at the A sites and W and Cr are doped at the B sites for ion doping. By adjusting the doping concentrations at the A and B sites, CBN piezoelectric ceramics with excellent and stable performance suitable for high-temperature environments are obtained.

[0007] In a specific implementation, Ce, W, and Cr-doped CBN ceramic powder is prepared using an oxide solid-state reaction method. First, the B-site doping concentration is fixed. Then, by varying the Ce doping concentration to obtain the optimal formulation, the W and Cr doping concentrations are further varied to obtain a Ce, W, and Cr composite ion-doped CBN sample. The piezoelectric ceramic obtained using this invention can be used to fabricate a piezoelectric accelerometer, which can operate for extended periods in a temperature range of 0–550 °C with highly stable performance.

[0008] Based on the above analysis, this invention provides a composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments. With Ca sites as A-sites and Nb sites as B-sites, Ce is doped at the A-sites, and W and Cr are doped at the B-sites, achieving co-doping at the A and B sites. Its general structural formula is represented as Ca... 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y O9, where 0.01≤x≤0.3; 0.01≤y≤0.03; x represents the doping concentration of Ce, and y represents the doping concentration of W and Cr.

[0009] In one feasible implementation, the preferred ranges for x and y are: 0.02≤x≤0.03; 0.02≤y≤0.03. When the ranges are 0.02≤x≤0.03 and 0.02≤y≤0.03, the piezoelectric coefficient can reach 17~18 pC / N, and the Curie temperature is above 930℃.

[0010] This invention also provides a method for preparing the above-mentioned composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments, which includes the following steps: (1) According to the general structural formula of composite ion-doped CBN piezoelectric ceramic materials, weigh the raw materials calcium carbonate (CaCO3), bismuth oxide (Bi2O3), niobium pentoxide (Nb2O5), cerium dioxide (CeO2), tungsten oxide (WO3) and chromium trioxide (Cr2O3), mix them, ball mill them for the first time, and then sinter them at 800~850 ℃ for 2~3 h to obtain the pre-fired powder; (2) The pre-fired powder is ball-milled, granulated, and pressed to obtain a composite ion-doped CBN ceramic green body; (3) After drying and removing the binder from the composite ion-doped CBN ceramic blank, it is sintered at 1100~1200 ℃ for 2~3 h to obtain composite ion-doped CBN ceramic; (4) Electrodes are fabricated on both sides of the obtained composite ion-doped CBN ceramic, and then electric field polarization is performed to obtain composite ion-doped CBN piezoelectric ceramic material.

[0011] In one possible implementation, for step (1), anhydrous ethanol is used as the medium during the first ball milling process, the weight ratio of anhydrous ethanol to powder is 2:1, and the ball milling conditions are: rotation speed 100~600 rpm and time 16~18h.

[0012] The slurry obtained from the first ball milling is dried and then placed in a sintering furnace, where it is heated to 800-850 ℃ at a heating rate of 2-5 ℃ / min.

[0013] In one possible implementation, for step (2), during the second ball milling process, anhydrous ethanol is used as the medium, the weight ratio of anhydrous ethanol to powder is 2:1, and the ball milling conditions are: rotation speed 400~600 rpm and time 16~18 h.

[0014] The slurry obtained from the second ball milling is dried, then polyvinyl alcohol solution is added as a binder. After thorough mixing, the mixture is granulated and passed through a 40-mesh sieve. The polyvinyl alcohol solution is obtained by dissolving polyvinyl alcohol in water, with a concentration of 8-10 wt.%. The amount of polyvinyl alcohol solution added is 4%-8% of the powder weight.

[0015] The granules obtained from granulation are placed on a press and dry-pressed at 150~200 MPa to obtain sheet-like composite ion-doped CBN ceramic green bodies.

[0016] In one possible implementation, for step (3), the composite ion-doped CBN ceramic preform is first heated to 120-130 ℃ at a heating rate of 2-3 ℃ / min and held for 1-2 h to remove moisture; then the preform is heated to 650-700 ℃ at a heating rate of 2-3 ℃ / min and held for 2-3 h to remove the adhesive.

[0017] Then, the ceramic preform after debinding is heated to 1000-1050 ℃ at a heating rate of 2-5 ℃ / min, and then heated to 1100-1200 ℃ at a heating rate of 2-3 ℃ / min and held for 2-3 h to complete the secondary sintering, thus obtaining composite ion-doped CBN ceramic.

[0018] In one feasible method, for step (4), the obtained composite ion-doped CBN ceramic is double-sided milled and polished, then coated with silver paste, and then held at 700~750 ℃ ​​for 10~20 min to form an electrode. The composite ion-doped CBN ceramic sample with the electrode is then placed in silicone oil at 140~150 ℃ for DC electric field polarization to obtain the final composite ion-doped CBN piezoelectric ceramic material. The electric field polarization conditions are: electric field strength 10~15 kV / mm, holding time 15~30 min.

[0019] Compared with existing technologies, the composite ion-doped CBN piezoelectric ceramic material and its preparation method suitable for ultra-high temperature service environments provided by this invention have the following beneficial effects: (1) The composite ion-doped CBN piezoelectric ceramic material provided by the present invention has the general structural formula Ca 1- x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y The synergistic effect of O9, Ce, W, and Cr composite ions can induce the transformation of the crystal structure from an orthorhombic phase to a pseudo-orthorhombic phase, enhancing the symmetry of the crystal structure and making the ceramic more conducive to domain flipping during polarization, thereby improving the piezoelectric performance; moreover, the Curie temperature of the doped CBN piezoelectric ceramic material can be maintained above 930℃, thus meeting the performance stability requirements of piezoelectric ceramics under high temperature conditions. (2) The composite ion-doped CBN piezoelectric ceramic material provided by the present invention has the general structural formula Ca 1- x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y O9, with Ce doped at the Ca site, reduces the oxygen vacancy concentration because the ionic radius of Ce is smaller than that of Ca, thereby reducing dielectric loss. (3) The composite ion-doped CBN piezoelectric ceramic material provided by this invention exhibits a sudden increase in orthogonality at x=0.02 and y=0.02, which improves the symmetry of the crystal structure and creates a structural environment conducive to polarization reversal. Simultaneously, Ce ion doping reduces oxygen vacancies and alleviates the pinning effect of electric domains. The synergistic effect of these two factors enhances the d... 33Highest.

[0020] (4) The composite ion-doped CBN piezoelectric ceramic material provided by the present invention has very low dielectric loss at high temperature, which can meet the application environment requirements of high temperature piezoelectric acceleration sensor and has good application prospects; it can also be used in sensitive elements such as transducers and detonators. Attached Figure Description

[0021] Figure 1 The Ca prepared in Examples 1, 2, 3, 4, and 5 of this invention 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y The O9 sample naturally shows the SEM image; where (a) corresponds to CBNWCr-C1, (b) corresponds to CBNWCr-C2, (c) corresponds to CBNWCr-C3, (d) corresponds to CCBN-WCr1, and (e) corresponds to CCBN-WCr3. Figure 2 The Ca prepared in Examples 1-5 of this invention 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y XRD patterns of O9 series piezoelectric ceramics; where (a) corresponds to CBNWCr-C1, CBNWCr-C2, and CBNWCr-C3, and (b) corresponds to CCBN-WCr1, CCBN-WCr2 (also known as CBNWCr-C2), and CCBN-WCr3. Figure 3 The Ca prepared in Examples 1-5 of this invention 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y The cell parameters a, b, c and orthogonality a / b of the O9 series piezoelectric ceramics; where (a) corresponds to the cell parameters of CBNWCr-C1, CBNWCr-C2, and CBNWCr-C3, (b) corresponds to the orthogonality of CBNWCr-C1, CBNWCr-C2, and CBNWCr-C3, (c) corresponds to the cell parameters of CCBN-WCr1, CCBN-WCr2 (also known as CBNWCr-C2), and CCBN-WCr3, and (d) corresponds to the orthogonality of CCBN-WCr1, CCBN-WCr2 (also known as CBNWCr-C2), and CCBN-WCr3. Figure 4The Ca prepared in Examples 1-5 of this invention 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y Dielectric temperature spectrum of O9 series piezoelectric ceramics; where (a) corresponds to CBNWCr-C1, (b) corresponds to CBNWCr-C2, (c) corresponds to CBNWCr-C3, (d) corresponds to CCBN-WCr1, and (e) corresponds to CCBN-WCr3. Detailed Implementation

[0022] The following will provide embodiments of the present invention with reference to the accompanying drawings, and further elaborate and describe the technical solution of the present invention through these embodiments. The following embodiments are merely a part of the embodiments of the present invention. Based on the content of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] The structural formula of the composite ion-doped CBN piezoelectric ceramic material designed in this embodiment is Ca. 0.99 Ce 0.01 Bi2Nb 1.98 (W 2 / 3 Cr 1 / 3 ) 0.02 O9, i.e., x=0.01, y=0.02, based on the above general structural formula, the preparation steps of the composite ion-doped CBN piezoelectric ceramic material provided in this embodiment are as follows:

[0025] (1) According to the general structural formula of composite ion-doped CBN piezoelectric ceramic materials, weigh the raw materials calcium carbonate (CaCO3), bismuth oxide (Bi2O3), niobium pentoxide (Nb2O5), cerium dioxide (CeO2), tungsten oxide (WO3), and chromium trioxide (Cr2O3), place them in a polytetrafluoroethylene ball mill jar, use anhydrous ethanol as the medium, and the weight ratio of anhydrous ethanol to powder is 2:1. Place the jar in a planetary ball mill and ball mill at a speed of 600 rpm for 16 h. After removing the slurry, dry it in an oven at 80 ℃, then place it in an alumina crucible and place it in a box furnace. Heat the slurry to 850 ℃ at a heating rate of 5 ℃ / min and hold it at that temperature for 3 h to complete the pre-sintering.

[0026] (2) The pre-fired powder was placed in a polytetrafluoroethylene ball mill jar with anhydrous ethanol as the dispersion medium. The weight ratio of anhydrous ethanol to powder was 2:1. The powder was ball-milled at 600 rpm for 16 h. The slurry was then dried in an oven at 80°C. A polyvinyl alcohol solution with a concentration of 8 wt.% was added to the powder as a binder, based on 4% of the powder weight. The powder was then granulated after thorough mixing and passed through a 40-mesh sieve. The resulting granules were then placed on a press and dry-pressed at 150 MPa to obtain a circular sheet with a diameter of about 10 mm and a thickness of about 1 mm, which is the composite ion-doped CBN ceramic blank.

[0027] (3) Arrange the blanks neatly in a box furnace, heat them to 120 ℃ at a heating rate of 2 ℃ / min and hold for 1 h to remove moisture, then heat them to 650 ℃ at a heating rate of 2 ℃ / min and hold for 2 h to remove adhesive; after cooling naturally in the furnace, stack the blanks together (5 pieces as a group), cover them with an alumina crucible and place them in a box furnace. Heat them to 1000 ℃ at a heating rate of 5 ℃ / min, then heat them to 1150 ℃ at a heating rate of 2 ℃ / min and hold for 3 h to complete the secondary sintering and obtain composite ion-doped CBN ceramics.

[0028] (4) The obtained ceramic was ground and polished on both sides to a thickness of about 0.5 mm, and then brushed with silver paste with a concentration of 10 wt.%. Then, it was heated in a box furnace at 700 ℃ for 10 min to form an electrode. The obtained sample was then placed in silicone oil at 150 ℃ for DC electric field polarization. The electric field polarization conditions were: electric field strength 15 kV / mm, holding time 30 min. The final composite ion-doped CBN piezoelectric ceramic material was denoted as CBNWCr-C1.

[0029] Example 2

[0030] The general structural formula of the composite ion-doped CBN piezoelectric ceramic material designed in this embodiment is Ca. 0.98 Ce 0.02 Bi2Nb 1.98 (W 2 / 3 Cr 1 / 3 ) 0.02 O9, i.e., x=0.02, y=0.02, based on the above general structural formula, the preparation steps of the composite ion-doped CBN piezoelectric ceramic material provided in this embodiment are as follows:

[0031] (1) According to the general structural formula of composite ion-doped CBN piezoelectric ceramic materials, weigh the raw materials calcium carbonate (CaCO3), bismuth oxide (Bi2O3), niobium pentoxide (Nb2O5), cerium dioxide (CeO2), tungsten oxide (WO3), and chromium trioxide (Cr2O3), place them in a polytetrafluoroethylene ball mill jar, use anhydrous ethanol as the medium, and the weight ratio of anhydrous ethanol to powder is 2:1. Place the jar in a planetary ball mill and ball mill at a speed of 600 rpm for 16 h. After removing the slurry, dry it in an oven at 80 ℃, then place it in an alumina crucible and place it in a box furnace. Heat the slurry to 850 ℃ at a heating rate of 5 ℃ / min and hold it at that temperature for 3 h to complete the pre-sintering.

[0032] (2) The pre-fired powder was placed in a polytetrafluoroethylene ball mill jar with anhydrous ethanol as the dispersion medium. The weight ratio of anhydrous ethanol to powder was 2:1. The powder was ball-milled at 600 rpm for 16 h. The slurry was then dried in an oven at 80°C. A polyvinyl alcohol solution with a concentration of 8 wt.% was added to the powder as a binder, based on 4% of the powder weight. The powder was then granulated after thorough mixing and passed through a 40-mesh sieve. The resulting granules were then placed on a press and dry-pressed at 150 MPa to obtain a circular sheet with a diameter of about 10 mm and a thickness of about 1 mm, which is the composite ion-doped CBN ceramic blank.

[0033] (3) Arrange the blanks neatly in a box furnace, heat them to 120 ℃ at a heating rate of 2 ℃ / min and hold for 1 h to remove moisture, then heat them to 650 ℃ at a heating rate of 2 ℃ / min and hold for 2 h to remove adhesive; after cooling naturally in the furnace, stack the blanks together (5 pieces as a group), cover them with an alumina crucible and place them in a box furnace. Heat them to 1000 ℃ at a heating rate of 5 ℃ / min, then heat them to 1150 ℃ at a heating rate of 2 ℃ / min and hold for 3 h to complete the secondary sintering and obtain composite ion-doped CBN ceramics.

[0034] (4) The obtained ceramic was ground and polished on both sides to a thickness of about 0.5 mm, and then brushed with silver paste with a concentration of 10 wt.%. Then, it was heated in a box furnace at 700 ℃ for 10 min to form an electrode. The obtained sample was then placed in silicone oil at 150 ℃ for DC electric field polarization. The electric field polarization conditions were: electric field strength 15 kV / mm, holding time 30 min. The final composite ion-doped CBN piezoelectric ceramic material was denoted as CBNWCr-C2.

[0035] Example 3

[0036] The structural formula of the composite ion-doped CBN piezoelectric ceramic material designed in this embodiment is Ca. 0.97 Ce 0.03 Bi2Nb 1.98(W 2 / 3 Cr 1 / 3 ) 0.02 O9, i.e., x=0.03, y=0.02, based on the above general structural formula, the preparation steps of the composite ion-doped CBN piezoelectric ceramic material provided in this embodiment are as follows:

[0037] (1) According to the general structural formula of composite ion-doped CBN piezoelectric ceramic materials, weigh the raw materials calcium carbonate (CaCO3), bismuth oxide (Bi2O3), niobium pentoxide (Nb2O5), cerium dioxide (CeO2), tungsten oxide (WO3), and chromium trioxide (Cr2O3), place them in a polytetrafluoroethylene ball mill jar, use anhydrous ethanol as the medium, and the weight ratio of anhydrous ethanol to powder is 2:1. Place the jar in a planetary ball mill and ball mill at a speed of 600 rpm for 16 h. After removing the slurry, dry it in an oven at 80 ℃, then place it in an alumina crucible and place it in a box furnace. Heat the slurry to 850 ℃ at a heating rate of 5 ℃ / min and hold it at that temperature for 3 h to complete the pre-sintering.

[0038] (2) The pre-fired powder was placed in a polytetrafluoroethylene ball mill jar with anhydrous ethanol as the dispersion medium. The weight ratio of anhydrous ethanol to powder was 2:1. The powder was ball-milled at 600 rpm for 16 h. The slurry was then dried in an oven at 80°C. A polyvinyl alcohol solution with a concentration of 8 wt.% was added to the powder as a binder, based on 4% of the powder weight. The powder was then granulated after thorough mixing and passed through a 40-mesh sieve. The resulting granules were then placed on a press and dry-pressed at 150 MPa to obtain a circular sheet with a diameter of about 10 mm and a thickness of about 1 mm, which is the composite ion-doped CBN ceramic blank.

[0039] (3) Arrange the blanks neatly in a box furnace, heat them to 120 ℃ at a heating rate of 2 ℃ / min and hold for 1 h to remove moisture, then heat them to 650 ℃ at a heating rate of 2 ℃ / min and hold for 2 h to remove adhesive; after cooling naturally in the furnace, stack the blanks together (5 pieces as a group), cover them with an alumina crucible and place them in a box furnace. Heat them to 1000 ℃ at a heating rate of 5 ℃ / min, then heat them to 1150 ℃ at a heating rate of 2 ℃ / min and hold for 3 h to complete the secondary sintering and obtain composite ion-doped CBN ceramics.

[0040] (4) The obtained ceramic was ground and polished on both sides to a thickness of about 0.5 mm, and then brushed with silver paste with a concentration of 10 wt.%. Then, it was heated in a box furnace at 700 ℃ for 10 min to form an electrode. The obtained sample was then placed in silicone oil at 150 ℃ for DC electric field polarization. The electric field polarization conditions were: electric field strength 15 kV / mm, holding time 30 min. The final composite ion-doped CBN piezoelectric ceramic material was denoted as CBNWCr-C3.

[0041] Example 4

[0042] The general structural formula of the composite ion-doped CBN piezoelectric ceramic material designed in this embodiment is Ca. 0.98 Ce 0.02 Bi2Nb 1.99 (W 2 / 3 Cr 1 / 3 ) 0.01 O9, i.e., x=0.02, y=0.01, based on the above general structural formula, the preparation steps of the composite ion-doped CBN piezoelectric ceramic material provided in this embodiment are as follows:

[0043] (1) According to the general structural formula of the composite ion-doped CBN piezoelectric ceramic material, weigh the raw materials calcium carbonate (CaCO3), bismuth oxide (Bi2O3), niobium pentoxide (Nb2O5), cerium dioxide (CeO2), tungsten oxide (WO3), and chromium trioxide (Cr2O3), place them in a polytetrafluoroethylene ball mill jar, use anhydrous ethanol as the medium, and add anhydrous ethanol to powder in a weight ratio of 2:1. Place the jar in a planetary ball mill and ball mill at a speed of 600 rpm for 16 h. After removing the slurry, dry it in an oven at 80 ℃, then place it in an alumina crucible and place it in a box furnace. Heat the slurry to 850 ℃ at a heating rate of 5 ℃ / min and hold it at that temperature for 3 h to complete the pre-sintering.

[0044] (2) The pre-fired powder was placed in a polytetrafluoroethylene ball mill jar with anhydrous ethanol as the dispersion medium. The weight ratio of anhydrous ethanol to powder was 2:1. The powder was ball-milled at 600 rpm for 16 h. The slurry was then dried in an oven at 80°C. A polyvinyl alcohol solution with a concentration of 8 wt.% was added to the powder as a binder, based on 4% of the powder weight. The powder was then granulated after thorough mixing and passed through a 40-mesh sieve. The resulting granules were then placed on a press and dry-pressed at 150 MPa to obtain a circular sheet with a diameter of about 10 mm and a thickness of about 1 mm, which is the composite ion-doped CBN ceramic blank.

[0045] (3) Arrange the blanks neatly in a box furnace, heat them to 120 ℃ at a heating rate of 2 ℃ / min and hold for 1 h to remove moisture, then heat them to 650 ℃ at a heating rate of 2 ℃ / min and hold for 2 h to remove adhesive; after cooling naturally in the furnace, stack the blanks together (5 pieces as a group), cover them with an alumina crucible and place them in a box furnace. Heat them to 1000 ℃ at a heating rate of 5 ℃ / min, then heat them to 1150 ℃ at a heating rate of 2 ℃ / min and hold for 3 h to complete the secondary sintering and obtain composite ion-doped CBN ceramics.

[0046] (4) The obtained ceramic was ground and polished on both sides to a thickness of about 0.5 mm, and then brushed with silver paste with a concentration of 10 wt.%. Then, it was heated in a box furnace at 700 ℃ for 10 min to form an electrode. The obtained sample was then placed in silicone oil at 150 ℃ for DC electric field polarization. The electric field polarization conditions were: electric field strength 15 kV / mm, holding time 30 min. The final composite ion-doped CBN piezoelectric ceramic material was denoted as CCBN-WCr1.

[0047] Example 5

[0048] The structural formula of the composite ion-doped CBN piezoelectric ceramic material designed in this embodiment is Ca. 0.98 Ce 0.02 Bi2Nb 1.97 (W 2 / 3 Cr 1 / 3 ) 0.03 O9, i.e., x=0.02, y=0.03, based on the above general structural formula, the preparation steps of the composite ion-doped CBN piezoelectric ceramic material provided in this embodiment are as follows:

[0049] (1) According to the general structural formula of the composite ion-doped CBN piezoelectric ceramic material, weigh the raw materials calcium carbonate (CaCO3), bismuth oxide (Bi2O3), niobium pentoxide (Nb2O5), cerium dioxide (CeO2), tungsten oxide (WO3), and chromium trioxide (Cr2O3), place them in a polytetrafluoroethylene ball mill jar, use anhydrous ethanol as the medium, and add anhydrous ethanol to powder in a weight ratio of 2:1. Place the jar in a planetary ball mill and ball mill at a speed of 600 rpm for 16 h. After removing the slurry, dry it in an oven at 80 ℃, then place it in an alumina crucible and place it in a box furnace. Heat the slurry to 850 ℃ at a heating rate of 5 ℃ / min and hold it at that temperature for 3 h to complete the pre-sintering.

[0050] (2) The pre-fired powder was placed in a polytetrafluoroethylene ball mill jar with anhydrous ethanol as the dispersion medium. The weight ratio of anhydrous ethanol to powder was 2:1. The powder was ball-milled at 600 rpm for 16 h. The slurry was then dried in an oven at 80°C. A polyvinyl alcohol solution with a concentration of 8 wt.% was added to the powder as a binder, based on 4% of the powder weight. The powder was then granulated after thorough mixing and passed through a 40-mesh sieve. The resulting granules were then placed on a press and dry-pressed at 150 MPa to obtain a circular sheet with a diameter of about 10 mm and a thickness of about 1 mm, which is the composite ion-doped CBN ceramic blank.

[0051] (3) Arrange the blanks neatly in a box furnace, heat them to 120 ℃ at a heating rate of 2 ℃ / min and hold for 1 h to remove moisture, then heat them to 650 ℃ at a heating rate of 2 ℃ / min and hold for 2 h to remove adhesive; after cooling naturally in the furnace, stack the blanks together (5 pieces as a group), cover them with an alumina crucible and place them in a box furnace. Heat them to 1000 ℃ at a heating rate of 5 ℃ / min, then heat them to 1150 ℃ at a heating rate of 2 ℃ / min and hold for 3 h to complete the secondary sintering and obtain composite ion-doped CBN ceramics.

[0052] (4) The obtained ceramic was ground and polished on both sides to a thickness of about 0.5 mm, and then brushed with silver paste with a concentration of 10 wt.%. Then, it was heated in a box furnace at 700 ℃ for 10 min to form an electrode. The obtained sample was then placed in silicone oil at 150 ℃ for DC electric field polarization. The electric field polarization conditions were: electric field strength 15 kV / mm, holding time 30 min. The final composite ion-doped CBN piezoelectric ceramic material was denoted as CCBN-WCr3.

[0053] The structures and properties of the samples prepared in Examples 1-5 above were characterized.

[0054] (a) Structural characterization

[0055] Observation of Ca under sintering conditions at 1150 ℃ using a scanning electron microscope (JSM-5900) 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y The morphology of the natural surface of the O9 sample, such as Figure 1 As shown, the grain morphology of all samples is lamellar, similar to that of bismuth layered compounds. Each grain exhibits random orientation and high anisotropy, a typical characteristic of bismuth layered piezoelectric ceramics. Furthermore, grain refinement is clearly observed with increasing doping concentration.

[0056] The phase structure of each sample was analyzed using an X-ray diffractometer (DX-2700 model), such as... Figure 2 As shown. It can be found that Ca 1- x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) yThe O9 series piezoelectric ceramics exhibit good crystallinity, with the main crystalline phase being calcium bismuth niobate-CaBi₂Nb₂O₉ (JCPDS#49-0608) with an orthorhombic structure and space group A21am. The strongest diffraction peak is (1 1 5), indicating its typical two-layer structure. Its main diffraction peaks are consistent with the standard diffraction chart for CaBi₂Nb₂O₉ and no impurity peaks are observed, indicating that the Ce, W, and Cr composite ions are well integrated into the crystal lattice. Furthermore, with increasing doping concentration, Ca… 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y The merging of the (200) diffraction peaks of the O9 series piezoelectric ceramics indicates that the Ce, W, and Cr composite ions can induce the crystal structure to transform from an orthorhombic phase to a pseudo-orthorhombic phase, which enhances the symmetry of the crystal structure and makes the ceramic more conducive to domain flipping during polarization, thereby improving the piezoelectric performance.

[0057] Using Jade software to analyze Ca 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y The XRD patterns of the O9 series piezoelectric ceramics were analyzed, such as... Figure 3 As shown in the figure, the results indicate that the cell parameters a, b, and c gradually decrease with increasing Ce, W, and Cr doping concentrations, suggesting overall lattice shrinkage. Notably, regardless of the Ce(x) or W and Cr(y) doping concentrations, a sudden increase in orthogonality (a / b) is observed at x=0.02 and y=0.02, although the overall trend is upward. This anomaly suggests that at this concentration, the degree of lattice distortion and defect concentration achieve a synergistic optimization effect, leading to a peak in piezoelectric performance at this concentration.

[0058] (II) Electrical performance characterization

[0059] The Curie temperature (T) of each sample was measured using a TH2838H impedance analyzer. c ), dielectric constant (ε) r And dielectric loss (tanδ) The results are as follows Figure 4 As shown in Table 1. Figure 4 The dielectric constant (ɛ) of each component ceramic sample rThe relationship between dielectric constant and loss (tanδ) and temperature and frequency is shown. With increasing temperature, both dielectric constant and loss increase to varying degrees. The dielectric constant of each ceramic sample reaches a peak around 930 °C, corresponding to the Curie temperature, which is the temperature point of the ferroelectric-paraelectric phase transition. For bismuth layered ceramics, the Curie temperature is closely related to lattice distortion; the greater the degree of lattice distortion, the higher the Curie temperature. (Ca...) 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y The relative permittivity (ɛ) of O9 ceramics r Both dielectric loss (tanδ) and dielectric constant decrease with increasing frequency. The dielectric loss of BLSFs is mainly due to oxygen vacancies, particularly in niobium-oxygen octahedra and (Bi₂O₂). 2+ Oxygen vacancies can be induced in both layers. This is because the ionic radius of Ce is smaller than that of Ca (Ca...). 2+ Ionic radius = 100 pm, Ce 4+ With an ionic radius of 94 pm, the oxygen vacancy concentration is reduced, thus leading to a decrease in dielectric loss.

[0060] The longitudinal piezoelectric constant (d) of each sample at room temperature was measured using a quasi-static piezoelectric constant tester (ZJ-6A). 33 The results are shown in Table 1.

[0061] Table 1 Ca 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y Electrical properties of O9 series piezoelectric ceramics

[0062]

[0063] The results show that when the doping concentration is x=0.02 and y=0.02, d 33 The maximum value can reach 18 pC / N. Therefore, the composite ion-doped CBN piezoelectric ceramic material prepared in this invention exhibits excellent electrical properties and a high piezoelectric constant. Compared to pure CBN (d) prepared using the traditional oxide solid-state reaction method, it achieves significantly higher piezoelectricity. 33 ~5 pC / N) piezoelectric ceramics. The piezoelectric coefficient of the composite ion-doped CBN piezoelectric ceramic material obtained after the doping modification of this invention is significantly improved, d 33 It can reach 18 pC / N, and the Curie temperature T after doping is cIt can maintain a temperature above 930 °C, and the dielectric loss tan δ also decreases to a certain extent. The dielectric loss at 500 °C is lower than that of pure CBN, which can fully meet the needs of high temperature piezoelectric applications.

Claims

1. A composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments, characterized in that, The general structural formula is represented as Ca 1-x Ce x Bi2Nb 2-y (W 2 / 3 Cr 1 / 3 ) y O9, where 0.01≤x≤0.3; 0.01≤y≤0.03; x represents the doping concentration of Ce, and y represents the doping concentration of W and Cr.

2. The composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments and its preparation method according to claim 1, characterized in that... When the range is 0.02≤x≤0.03 and 0.02≤y≤0.03, the piezoelectric coefficient can reach 17~18 pC / N, and the Curie temperature is above 930 ℃.

3. A method for preparing a composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments as described in claim 1 or 2, characterized in that, Includes the following steps: (1) According to the general structural formula of composite ion-doped CBN piezoelectric ceramic materials, weigh the raw materials calcium carbonate, bismuth oxide, niobium pentoxide, cerium dioxide, tungsten oxide and chromium trioxide, mix them and ball mill them for the first time, and then sinter them at 800~850 ℃ for 2~3 h to obtain the pre-fired powder. (2) The pre-fired powder is ball-milled, granulated, and pressed to obtain a composite ion-doped CBN ceramic green body; (3) After drying and removing the binder from the composite ion-doped CBN ceramic blank, it is sintered at 1100~1200 ℃ for 2~3 h to obtain composite ion-doped CBN ceramic; (4) Electrodes are fabricated on both sides of the obtained composite ion-doped CBN ceramic, and then electric field polarization is performed to obtain composite ion-doped CBN piezoelectric ceramic material.

4. The preparation method of composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments according to claim 3, characterized in that, For step (1), anhydrous ethanol is used as the medium in the first ball milling process, and the ball milling conditions are: rotation speed 100~600 rpm and time 16~18 h.

5. The method for preparing composite ion-doped CBN piezoelectric ceramic materials suitable for ultra-high temperature service environments according to claim 3, characterized in that, For step (2), during the second ball milling process, anhydrous ethanol is used as the medium, and the ball milling conditions are: rotation speed 400~600 rpm and time 16~18 h.

6. The method for preparing composite ion-doped CBN piezoelectric ceramic materials suitable for ultra-high temperature service environments according to claim 3, characterized in that, Polyvinyl alcohol solution was added to the powder obtained from the second ball milling as a binder, and the mixture was thoroughly mixed before granulation. The polyvinyl alcohol solution was obtained by dissolving polyvinyl alcohol in water and had a concentration of 8-10 wt.%.

7. The method for preparing composite ion-doped CBN piezoelectric ceramic materials suitable for ultra-high temperature service environments according to claim 6, characterized in that, The amount of polyvinyl alcohol solution added is 4% to 8% of the powder weight.

8. The method for preparing composite ion-doped CBN piezoelectric ceramic materials suitable for ultra-high temperature service environments according to claim 3, characterized in that, For step (2), the granules obtained by granulation are placed on a press and dry-pressed at 150~200 MPa to obtain a sheet-like composite ion-doped CBN ceramic preform.

9. The method for preparing composite ion-doped CBN piezoelectric ceramic materials suitable for ultra-high temperature service environments according to claim 3, 6, or 7, characterized in that, For step (3), the ceramic blank after debinding is heated to 1000-1050 ℃ at a heating rate of 2-5 ℃ / min, and then heated to 1100-1200 ℃ at a heating rate of 2-3 ℃ / min and held for 2-3 h to complete the secondary sintering, thereby obtaining composite ion-doped CBN ceramic.

10. The preparation method of the composite ion-doped CBN piezoelectric ceramic material suitable for ultra-high temperature service environments according to claim 3, characterized in that, For step (4), the electric field polarization conditions are: electric field strength 10~15 kV / mm, voltage holding time 15~30 min.

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