Preparation method of high-temperature piezoelectric ceramics with large electrostrictive strain under low driving electric field

Abstract

The present invention provides a preparation method for a high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field. BaCO3, TiO2, SnO2, and MnO2 are proportioned according to the chemical formula Ba(Sn 0.11 Ti 0.89 )O3, and 0.6 wt.% MnO2 is added. After ball milling and sieving, sintering is carried out at 1080 - 1120 °C. After ball milling again, granulation is performed, and then sintering is carried out at 1360 - 1400 °C. BaCO3, TiO2, HfO2, Fe2O3, Fe3O4, Bi2O3, SrCO3, and La2O3 are proportioned according to the chemical formula 0.679BiFeO3 - 0.291BaHf 0.05 Ti 0.95 O3 - 0.03(La 0.1 Sr 0.8 )TiO 3‑δ . After proportioning, ball milling, and drying, pre-sintering is carried out at 780 - 820 °C. After ball milling again, granulation is performed, and then sintering is carried out at 1060 - 1100 °C. 3 - 9% of the second ferroelectric phase is added to 91 - 97% of the relaxor ferroelectric matrix phase by weight percentage. After ball milling, drying, granulation, tabletting, and finally sintering. The present invention can prepare a 0-3 type composite piezoelectric ceramic with excellent electrostrictive strain performance under a low driving electric field.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric ceramic preparation, and particularly relates to a preparation method of a high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field. Background Art

[0002] The lead-free high-temperature piezoelectric ceramic (1-x)BiFeO3-xBaTiO3 has a high Curie temperature (>450°C) and is favored by researchers. However, during the sintering process, the volatilization of Bi 3+ and the reduction of Fe 3+ result in the easy formation of a second phase with a low bandgap width in the preparation of this piezoelectric ceramic; in addition, the ceramics of this system have a high coercive field, so it is difficult to test their intrinsic electrostrictive strain performance.

[0003] In recent years, researchers have constructed 0-3 composite ceramics by introducing ferroelectric phases into relaxor ferroelectric ceramics, and used the strain coupling and polarization coupling effects to reduce the energy required for domain deflection, so as to obtain excellent electrostrictive strain performance under a low driving external electric field. For example, Zhang Haibo et al. introduced the ferroelectric phase 93BNT-7BT into the relaxor ferroelectric phase 91BNT-6BT-3AN to construct 0-3 composite ceramics, and obtained excellent electrostrictive strain performance under a low driving electric field; Groh et al. introduced the ferroelectric phase 0.93BNT-0.07BT into the relaxor ferroelectric phase 0.92BNT-0.06BT-0.02KNN to construct 0-3 composite ceramics, and obtained excellent electrostrictive strain S~0.38% (40 kV / cm) under a low driving electric field. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned prior art, the present invention aims to provide a preparation method of a high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field, so as to prepare a new 0-3 type composite piezoelectric ceramic with excellent electrostrictive strain performance under a low driving electric field.

[0005] In order to achieve the above object, the present invention provides a preparation method of a high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field, including the following steps:

[0006] S1. Prepare the ferroelectric second phase:

[0007] Weigh the raw materials BaCO3, TiO2, SnO2, MnO2 according to the chemical formula Ba(Sn 0.11 Ti 0.89 )O3, add 0.6 wt.% MnO2, mix and then ball mill, sieve, sinter at 1080-1120°C, ball mill again and granulate, sinter at 1360-1400°C, and then sieve for standby.

[0008] S2. Prepare the relaxor ferroelectric matrix phase:

[0009] Mix the raw materials BaCO3, TiO2, HfO2, Fe2O3, Fe3O4, Bi2O3, SrCO3, La2O3 according to the chemical formula 0.679BiFeO3-0.291BaHf 0.05 Ti 0.95 O3-0.03(La 0.1 Sr 0.8 )TiO 3-δ for batching, ball-mill after mixing, dry, then pre-sinter at 780 - 820 °C, granulate after ball-milling again, and sinter at 1060 - 1100 °C.

[0010] S3. Prepare 0-3 type composite piezoelectric ceramics:

[0011] Add 3 - 9% of the second ferroelectric phase by weight percentage to 91 - 97% of the relaxor ferroelectric matrix phase, then ball-mill, dry and granulate, press into tablets, and finally sinter at 1080 - 1084 °C to obtain 0-3 type composite piezoelectric ceramics.

[0012] In the above solution: In step S1, the first ball-milling time and the second ball-milling time are both 12 h.

[0013] In the above solution: In step S1, the first sintering temperature is 1100 °C and the time is 4 h; the second sintering temperature is 1380 °C and the time is 4 h.

[0014] In the above solution: In step S2, the first ball-milling time and the second ball-milling time are both 12 h.

[0015] In the above solution: In step S2, the first sintering temperature is 800 °C and the time is 5 h; the second sintering temperature is 1080 °C and the time is 2 h.

[0016] In the above solution: In step S3, the weight percentage of the second ferroelectric phase is 5%, and the weight percentage of the relaxor ferroelectric matrix phase is 95%. The 0-3 type composite piezoelectric ceramics prepared according to the above weight percentages can obtain extremely excellent electrostrictive properties.

[0017] In the above solution: In step S3, use a high-energy ball mill for ball-milling, and the ball-milling time is 15 min.

[0018] In the above solution: In step S3, the sintering temperature is 1082 °C and the time is 2 h.

[0019] The beneficial effects of the present invention are:

[0020] In the relaxor ferroelectric matrix phase without the composite second phase, under an external electric field, the electric domain deflection needs to cross a relatively high potential barrier, and the electric domain deflection needs to overcome the large frictional damping between domain walls and grain boundaries, so a large strain hysteresis is generated. At the same time, the electrostrictive strain obtained under a small external driving electric field is low. Only when the external driving electric field exceeds or is much greater than the coercive field, can the electric domains deflect more fully and the electrostrictive strain increase rapidly.

[0021] For the 0-3 type composite piezoelectric ceramics formed by ferroelectric second phase and relaxor ferroelectric phase, strain coupling will occur under the action of an external electric field. First, before testing the electrostrictive strain, the 0-3 type composite piezoelectric ceramics are polarized under a small electric field. After polarization, the residual strain of the ferroelectric second phase will generate a compressive stress acting on the relaxor ferroelectric matrix. Second, during the electrostrictive strain test, due to the secondary deformation of the ferroelectric second phase under the action of the external electric field, the stress applied to the nearby relaxor ferroelectric matrix will be enhanced. The stress will drive the domain growth of the relaxor ferroelectric matrix at the two-phase interface and drive a certain pre-deflection of some internal domain structures. This will drive the transformation of polar nano-regions into ferroelectric domains and the reorientation of ferroelectric domains with the external electric field, and drive the deflection and nucleation of electric domains under this strain coupling effect.

[0022] In the 0-3 type composite piezoelectric ceramics, in addition to strain coupling, there is also polarization coupling due to different dielectric constants. In an ideal 0-3 composite ceramic, it is considered that the ferroelectric second phase and the relaxor ferroelectric matrix are ideal insulators. Therefore, the ferroelectric second phase and the relaxor ferroelectric matrix are equivalent to a polarization coupling model of two capacitors in series. Since the ferroelectric phase has a higher dielectric constant than the relaxor ferroelectric matrix, under an external electric field, the partial voltage on the internal relaxor ferroelectric matrix will be greater than the external electric field, which is equivalent to reducing the applied driving electric field of the ceramic when obtaining the same strain.

[0023] In summary, a 0-3 type composite piezoelectric ceramic with excellent electrostrictive strain performance under a low driving electric field is prepared by the present invention. This method is expected to provide a new idea for the practical application of BiFeO3-BaTiO3-based piezoelectric ceramics. Brief Description of the Drawings

[0024] Figure 1 It is the unipolar S-E loop of the 0-3 type composite piezoelectric ceramic of the present invention. Among them: (a) x = 3wt.%; (b) x = 5wt.%; (c) x = 7wt.%; (d) x = 9wt.%.

[0025] Figure 2 It is the comparison diagram of electrostrictive strain loops of 0-3 type composite piezoelectric ceramics (x = 5wt.%) and uncomposited BF-BHT-LST ceramics. Among them: (a) 30kV / cm; (b) 40kV / cm; (c) 60kV / cm. Detailed implementation mode

[0026] Example 1

[0027] A preparation method of a high-temperature piezoelectric ceramic with large electrostrain under a low driving electric field mainly consists of the following steps:

[0028] S1. Prepare the ferroelectric second phase:

[0029] Mix the raw materials BaCO3 (purity 99.8%), TiO2 (purity 99.8%), SnO2 (purity 99.8%), and MnO2 (purity 98%) according to the chemical formula Ba(Sn 0.11 Ti 0.89 )O3, add 0.6 wt.% MnO2, ball mill for 12 h after mixing, sieve, sinter at 1100 °C for 4 h, ball mill again for 12 h and then granulate, sinter at 1380 °C for 4 h, and then sieve for standby.

[0030] S2. Prepare the relaxor ferroelectric matrix phase:

[0031] Mix the raw materials BaCO3 (purity 99.8%), TiO2 (purity 99.8%), HfO2 (purity 99%), Fe2O3 (purity 99%), Fe3O4 (purity 99%), Bi2O3 (purity 99%), SrCO3 (purity 99.8%), and La2O3 (purity 99.99%) according to the chemical formula 0.679BiFeO3-0.291BaHf 0.05 Ti 0.95 O3-0.03(La 0.1 Sr 0.8 )TiO 3-δ for batching, ball mill for 12 h after mixing, dry, then pre-sinter at 800 °C for 5 h, ball mill again for 12 h and then granulate, and sinter at 1080 °C for 2 h.

[0032] S3. Prepare the 0-3 type composite piezoelectric ceramic:

[0033] Add 5% of the ferroelectric second phase to 95% of the relaxor ferroelectric matrix phase by weight percentage, then ball mill in a high-energy ball mill for 15 min, dry and granulate, press into tablets, and finally sinter at 1082 °C for 2 h to obtain the 0-3 type composite piezoelectric ceramic.

[0034] Comparative example 1

[0035] A preparation method of a high-temperature piezoelectric ceramic with large electrostrain under a low driving electric field mainly consists of the following steps:

[0036] S1. Prepare the ferroelectric second phase:

[0037] Mix the raw materials BaCO3 (purity 99.8%), TiO2 (purity 99.8%), SnO2 (purity 99.8%), and MnO2 (purity 98%) according to the chemical formula Ba(Sn 0.11 Ti 0.89 )O3, add 0.6 wt.% MnO2, ball mill for 12 h after mixing, screen, sinter at 1100 °C for 4 h, and granulate after ball milling for another 12 h, then sinter at 1380 °C for 4 h, and then screen for standby.

[0038] S2. Prepare the relaxor ferroelectric matrix phase:

[0039] Mix the raw materials BaCO3 (purity 99.8%), TiO2 (purity 99.8%), HfO2 (purity 99%), Fe2O3 (purity 99%), Fe3O4 (purity 99%), Bi2O3 (purity 99%), SrCO3 (purity 99.8%), and La2O3 (purity 99.99%) according to the chemical formula 0.679BiFeO3 - 0.291BaHf 0.05 Ti 0.95 O3 - 0.03(La 0.1 Sr 0.8 )TiO 3-δ Perform batching, ball mill for 12 h after mixing, dry, then pre-sinter at 800 °C for 5 h, and granulate after ball milling for another 12 h, then sinter at 1080 °C for 2 h.

[0040] S3. Prepare the 0-3 type composite piezoelectric ceramic:

[0041] Add 3% of the ferroelectric second phase to 97% of the relaxor ferroelectric matrix phase by weight percentage, then ball mill in a high-energy ball mill for 15 min, dry and granulate, press into tablets, and finally sinter at 1082 °C for 2 h to obtain the 0-3 type composite piezoelectric ceramic.

[0042] Comparative Example 2

[0043] A preparation method of a high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field mainly consists of the following steps:

[0044] S1. Prepare the ferroelectric second phase:

[0045] Mix the raw materials BaCO3 (purity 99.8%), TiO2 (purity 99.8%), SnO2 (purity 99.8%), and MnO2 (purity 98%) according to the chemical formula Ba(Sn 0.11 Ti 0.89 )O3, add 0.6 wt.% MnO2, ball mill for 12 h after mixing, screen, sinter at 1100 °C for 4 h, and granulate after ball milling for another 12 h, then sinter at 1380 °C for 4 h, and then screen for standby.

[0046] S2. Prepare the relaxor ferroelectric matrix phase:

[0047] Charge the raw materials BaCO3 (purity 99.8%), TiO2 (purity 99.8%), HfO2 (purity 99%), Fe2O3 (purity 99%), Fe3O4 (purity 99%), Bi2O3 (purity 99%), SrCO3 (purity 99.8%), La2O3 (purity 99.99%) according to the chemical formula 0.679BiFeO3-0.291BaHf 0.05 Ti 0.95 O3-0.03(La 0.1 Sr 0.8 )TiO 3-δ Perform batching, ball mill for 12 h after mixing, dry, then pre-sinter at 800 °C for 5 h, and granulate after ball milling for 12 h again, and sinter at 1080 °C for 2 h.

[0048] S3. Prepare the 0-3 type composite piezoelectric ceramic:

[0049] Add 7% of the ferroelectric second phase to 93% of the relaxor ferroelectric matrix phase by weight percentage, then ball mill in a high-energy ball mill for 15 min, dry and granulate, press into tablets, and finally sinter at 1082 °C for 2 h to obtain the 0-3 type composite piezoelectric ceramic.

[0050] Comparative Example 3

[0051] A preparation method of a high-temperature piezoelectric ceramic with large electrostrain under a low driving electric field, mainly composed of the following steps:

[0052] S1. Prepare the ferroelectric second phase:

[0053] Charge the raw materials BaCO3 (purity 99.8%), TiO2 (purity 99.8%), SnO2 (purity 99.8%), MnO2 (purity 98%) according to the chemical formula Ba(Sn 0.11 Ti 0.89 )O3 for batching, and add 0.6 wt.% MnO2, ball mill for 12 h after mixing, sieve, sinter at 1100 °C for 4 h, and granulate after ball milling for 12 h again, and sinter at 1380 °C for 4 h, and then sieve for standby.

[0054] S2. Prepare the relaxor ferroelectric matrix phase:

[0055] Mix the raw materials BaCO3 (purity 99.8%), TiO2 (purity 99.8%), HfO2 (purity 99%), Fe2O3 (purity 99%), Fe3O4 (purity 99%), Bi2O3 (purity 99%), SrCO3 (purity 99.8%), La2O3 (purity 99.99%) according to the chemical formula 0.679BiFeO3 - 0.291BaHf 0.05 Ti 0.95 O3 - 0.03(La 0.1 Sr 0.8 )TiO 3-δ for batching. After mixing, ball mill for 12 h, dry, then pre - sinter at 800 °C for 5 h, and granulate after ball milling again for 12 h, and sinter at 1080 °C for 2 h.

[0056] S3. Preparation of 0 - 3 type composite piezoelectric ceramics:

[0057] Add 9% of the ferroelectric second phase to 91% of the relaxor ferroelectric matrix phase by weight percentage, then ball mill in a high - energy ball mill for 15 min, dry and granulate, press into tablets, and finally sinter at 1082 °C for 2 h to obtain 0 - 3 type composite piezoelectric ceramics.

[0058] Figure 1 shows the unipolar strain loop of the 0 - 3 type composite piezoelectric ceramics. It can be clearly seen from the figure that as the ferroelectric second phase increases, the maximum unipolar electro - strain gradually increases, and the most excellent electro - strain performance is obtained at x = 5 wt.% (x refers to the weight percentage of the ferroelectric second phase). When the external electric field is 30 kV / cm, the maximum unipolar electro - strain S max = 0.137%, the piezoelectric strain constant d 33 * = 457 pm / V and the normalized piezoelectric strain constant d 33 # = 400 pm / V; when the electric field is 40 kV / cm, the maximum unipolar electro - strain S max = 0.195%; when the electric field is 50 kV / cm, the maximum unipolar electro - strain S max = 0.225%; when the electric field is 60 kV / cm, the maximum unipolar electro - strain S max = 0.255%. When the external electric field exceeds 50 kV / cm, the electro - strain increases slowly. In addition, it can also be clearly observed from the figure that the strain hysteresis H (H = ΔS max / S max *100%) of the composite - phase ceramics gradually decreases, reaching the lowest value at x = 5 wt.%, H = 30% (30 kV / cm), and the strain hysteresis is as high as 80% (30 kV / cm) at x = 9 wt.% as the ferroelectric phase increases.

[0059] When the ferroelectric second phase is introduced at 5 wt.%, the electrostrictive properties of the 0-3 composite piezoelectric ceramics are the most excellent. Here, the electrostrictive curves of the 0-3 composite piezoelectric ceramics (x = 5 wt.%) and the non-composite BF-BHT-LST ceramics (x = 0 wt.%) are tested under electric fields of 30, 40, and 60 kV / cm as follows Figure 2 shown. It can be observed from the figure that when the electric field is 30 kV / cm, the electrostrictive strain difference ΔS between the 0-3 composite piezoelectric ceramics and the non-composite BF-BHT-LST ceramics is 0.051%; when the electric field is 40 kV / cm, the electrostrictive strain difference ΔS is 0.028%; however, when the electric field increases to 60 kV / cm, the electrostrictive strain difference ΔS between the 0-3 composite piezoelectric ceramics and the non-composite BF-BHT-LST ceramics is -0.065%. It shows that the electrostrictive strain in the 0-3 composite piezoelectric ceramics is significantly better than that of the non-composite relaxor ferroelectric ceramics at low electric fields. However, after exceeding a certain threshold, the electrostrictive strain of the relaxor ferroelectric ceramics rises rapidly and is significantly better than that of the 0-3 composite piezoelectric ceramics.

[0060] When x = 5 wt.%, at 30 kV / cm, the electrostrictive strain (0.137%) and the normalized piezoelectric strain constant (400 pm / V) of the 0-3 composite piezoelectric ceramics are increased by nearly 161% and 215% respectively compared with the electrostrictive strain (0.084%) and the normalized piezoelectric strain constant (186 pm / V) of the non-composite BF-BHT-LST ceramics; the strain hysteresis (30%) of the 0-3 composite piezoelectric ceramics is reduced by nearly 230% compared with the strain hysteresis (69%) of the non-composite BF-BHT-LST ceramics; the remnant strain (0.017%) of the 0-3 composite piezoelectric ceramics is reduced by nearly 165% compared with the remnant strain (0.028%) of the non-composite BF-BHT-LST ceramics.

Claims

1. A preparation method of a high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field, characterized in that It includes the following steps: S1. Prepare the ferroelectric second phase: Mix the raw materials BaCO3, TiO2, SnO2, and MnO2 according to the chemical formula Ba(Sn 0.11 Ti 0.89 )O3, add 0.6 wt.% MnO2, ball mill after mixing, screen, then sinter at 1080 - 1120 °C, granulate after ball milling again, sinter at 1360 - 1400 °C, and then screen for standby; S2. Prepare the relaxor ferroelectric matrix phase: Mix the raw materials BaCO3, TiO2, HfO2, Fe2O3, Fe3O4, Bi2O3, SrCO3, La2O3 according to the chemical formula 0.679BiFeO3-0.291BaHf 0.05 Ti 0.95 O3-0.03(La 0.1 Sr 0.8 )TiO 3-δ Perform batching, ball milling after mixing, drying, then pre-sintering at 780-820 °C, granulating after ball milling again, and sintering at 1060-1100 °C; S3. Prepare the 0-3 type composite piezoelectric ceramic: Add 5% of the ferroelectric second phase by weight percentage to 95% of the relaxor ferroelectric matrix phase, then ball mill, dry and granulate, press into tablets, and finally sinter at 1080-1084 °C to obtain the 0-3 type composite piezoelectric ceramic.

2. The preparation method of the high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field according to claim 1, characterized in that: In step S1, the first ball milling time and the second ball milling time are both 12 h.

3. The preparation method of the high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field according to claim 1, characterized in that: In step S1, the first sintering temperature is 1100 °C and the time is 4 h; the second sintering temperature is 1380 °C and the time is 4 h.

4. The preparation method of the high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field according to claim 1, characterized in that: In step S2, the first ball milling time and the second ball milling time are both 12 h.

5. The preparation method of the high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field according to claim 1, characterized in that: In step S2, the first sintering temperature is 800 °C and the time is 5 h; the second sintering temperature is 1080 °C and the time is 2 h.

6. The preparation method of the high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field according to claim 1, characterized in that: In step S3, use a high-energy ball mill for ball milling, and the ball milling time is 15 min.

7. The preparation method of the high-temperature piezoelectric ceramic with large electrostrictive strain under a low driving electric field according to claim 1, characterized in that: In step S3, the sintering temperature is 1082 °C and the time is 2 h.

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