CN104230333B - A kind of high temperature piezoceramics and preparation method thereof - Google Patents

Abstract

The invention discloses a piezoelectric ceramic with a high Curie temperature. The general formula of the piezoelectric ceramic is (BiYb) _1-x Pb _x Ti _y Zr _x-y O ₃ +zmol%A, where x=0.91-0.98, y= 0.45~0.68, z=0.05~5, A is a modifying element. The present invention also provides a method for preparing the piezoelectric ceramic, the piezoelectric ceramic prepared by the method has a higher Curie temperature, a higher piezoelectric constant, a lower dielectric loss, a higher electromechanical coupling coefficient and A wide range of variable mechanical quality factors, etc., and overcome the problems that existing piezoelectric materials are difficult to have high Curie temperature and high piezoelectric performance at the same time, and the comprehensive electrical parameters cannot meet the requirements of specific piezoelectric devices. The invention has the characteristics of simple and stable process, no need of special equipment, low cost, convenient large-scale industrial production, etc., and can be used for corresponding various high-temperature piezoelectric devices.

Description

A kind of high temperature piezoelectric ceramic material and preparation method thereof

technical field

The invention relates to the field of electronic ceramics and piezoelectric devices, in particular to a piezoelectric ceramic with a high Curie temperature and a preparation method thereof.

Background technique

The development of modern industry has put forward higher requirements for the high-temperature environment operation of various acoustic transducers and vibration sensors, which requires the piezoelectric materials used in these devices to have a higher Curie temperature (T _c ). For example, acoustic logging transducers used in oil wells, piezoelectric actuators and sensors used in spacecraft, fuel injection nozzle drivers, and various sensors used in other extreme environments all require _Tc above 380°C and even higher piezoelectric ceramics. The T _c of the most commonly used piezoelectric ceramic lead zirconate titanate (PZT) is generally much lower than 360°C. Because of the degradation of piezoelectric properties caused by the gradual depolarization of the material with increasing temperature, the upper limit of its working temperature is generally at 1/2 of its Curie temperature, so the service temperature of PZT is generally much lower than 180°C. Therefore, it is of great significance to study the preparation of piezoelectric ceramics with high Curie temperature for the preparation of high temperature piezoelectric devices.

In general, the higher the Curie temperature of a piezoelectric material, the worse its piezoelectric performance. For example, Chinese Patent Publication No. CN1295046 discloses a bismuth layered piezoelectric ceramic with a Curie temperature of 865° C., but its piezoelectric performance is very poor, and its piezoelectric constant d ₃₃ is only about 20 pC/N. In 2001, a perovskite structure piezoelectric ceramic composed of (1-x)BiScO ₃ -xPbTiO ₃ (BSPT) was reported (Japan Journal of Applied Physics, Vol40, pp5999-6002). Electrical properties and higher Curie temperature (at x=0.64, its d ₃₃ is about 460pC/N, and T _c is about 450°C). However, the raw material Sc ₂ O ₃ is extremely expensive. In addition, the piezoelectric material has poor comprehensive electrical properties (for example, the mechanical quality factor Q _m is too low, resulting in high energy consumption and severe heat generation during use), and unstable performance. This seriously restricts its practical application. Therefore, the preparation of piezoelectric ceramics with high Curie temperature (T _c >400℃), piezoelectric constant (d ₃₃ >460pC/N) and excellent comprehensive electrical properties (such as high Q _m and low loss) and related stable processes The development of it has always been a difficult problem to be solved in this field.

Contents of the invention

Aiming at the problems that existing piezoelectric ceramic materials are difficult to obtain high Curie temperature and high-voltage electrical properties at the same time, the comprehensive electrical properties cannot meet the requirements of device use at the same time, or the price is expensive, etc., the present invention provides a high Curie temperature, relatively high piezoelectric ceramic material. Coefficient, mechanical quality factor has been greatly improved and can be adjusted within a certain range, and a new type of doped low-cost high-temperature piezoelectric ceramic material with low dielectric loss.

The high Curie temperature piezoelectric ceramic material proposed by the present invention has the following general chemical structure formula: (BiYb) _1-x Pb _x Ti _y Zr _xy O ₃ +zmol%A, where x ranges from 0.91 to 0.98, The value range of y is 0.45-0.68, the value range of z is 0.05-5, and A is a modifying element, which can be a single metal element or multiple metal elements. When the ionic radius of the modifying element is smaller than the ionic radius of Yb and Ti metal elements, and it is a multivalent element, it has a better modifying effect, but the modifying element does not include Fe.

In particular, when the modifying element is one or more of Mn, Nb and Cr, the piezoelectric ceramic has better comprehensive properties.

For the preferred system, the value range of x is 0.91-0.98, the value range of y is 0.45-0.68, and the value range of z is 0.05-5. Piezoelectric ceramics within this range have more excellent performance. More preferably, the value range of z is 0.1-2.

The preparation method of the high Curie temperature piezoelectric ceramics comprises the following steps:

(1) Weigh Bi ₂ O ₃ , Yb ₂ O ₃ , Pb ₃ O ₄ , TiO ₂ , ZrO ₂ and oxides or salts of modifying elements in molar ratio, and then mix and grind to obtain raw material powder;

(2) pre-calcining the powder obtained in step (1) after drying, sieving, and fully grinding the block obtained by pre-calcining;

(3) drying, granulating, aging, and sieving the powder obtained by grinding in step (2) to form a ceramic green body;

(4) After debinding, the ceramic green body is sintered in a sealed crucible at a high temperature under normal pressure to obtain a piezoelectric ceramic body;

(5) After the fired piezoelectric ceramic body is ground, polished, and covered with silver electrodes, it is polarized at 100° C. to 180° C. and an electric field of 3 to 5 kV/mm.

Preferably, the corresponding oxides or salts of the modifying elements include MnCO ₃ , Nb ₂ O ₅ and Cr ₂ O ₃ .

The grinding method used in step (1) and step (2) is ball milling. Other mixed abrasive methods can also be used, such as mechanical vibration mill; during ball milling, the ratio of material: balls: liquid ball milling medium is about 1:1~2:0.5~2, and the ball milling time is about 6~24 hours.

The pre-burning temperature in step (2) is 700-900°C, and the pre-burning time is about 1.5-3 hours.

The adhesive used in step (3) is an aqueous solution with a mass fraction not greater than 6% PVA, and the aging time is not more than 12 hours.

The sintering temperature in step (4) is 1050-1280° C., and the sintering time is 2-5 hours. Preferably, the sintering temperature is 1100-1250°C, and the sintering time is 2-3 hours

In step (5), the polarization temperature is 100°C-180°C, the polarization electric field is about 3-5kV/mm, and the time is 20 minutes. Under this polarization condition, the prepared piezoelectric ceramic material has better performance.

The present invention provides a new type of high-temperature piezoelectric ceramics with high Curie temperature and excellent comprehensive piezoelectric performance composite perovskite (BiYb) _1-x Pb _x Ti _y Zr _xy O ₃ +zmol%A, which solves the problem of existing piezoelectric The Curie temperature and comprehensive piezoelectric properties of electric materials cannot meet the requirements of specific indicators at the same time. The piezoelectric ceramic also has a high Curie temperature (365-430°C), a high piezoelectric constant (170-330pC/N), a wide range of variable mechanical quality factors (50-500) and a low The dielectric loss is low (0.001-0.05), and it can be used in various piezoelectric devices such as transducers and sensors whose working temperature is above 210°C. Compared with other high-temperature piezoelectric ceramics, the preparation cost of the new piezoelectric ceramic is much lower, and it is a promising high-temperature piezoelectric material.

Description of drawings

Figure 1. Scanning electron microscope image of the sample obtained by (BiYb) _0.065 Pb _0.935 Ti _0.51 Zr _0.425 O ₃ +1.2mol%Mn sintered at 1100°C and kept for 2.5h.

Figure 2. The medium temperature spectrum of the sample obtained by sintering (BiYb) _0.07 Pb _0.93 Ti _0.47 Zr _0.46 O ₃ +0.1mol%Mn at 1100°C and holding for 2.5 hours.

detailed description

The preferred embodiments of the present invention are listed below, which are only used to explain the present invention rather than limit it.

Example 1:

Weigh Bi ₂ O ₃ , Yb ₂ O ₃ , Pb ₃ O ₄ , TiO ₂ , ZrO ₂ and MnCO ₃ according to the molar ratio of (BiYb) _0.07 Pb _0.93 Ti _0.49 Zr _0.44 O ₃ ++1mol%Mn, add anhydrous The ethanol medium is mixed with ball mill, dried and sieved, and pre-fired at 750°C for 2 hours. The pre-fired block is then ball milled, dried and granulated with 5% PVA, aged for 6 hours, sieved and pressed into a green body with a diameter of 15mm and a thickness of about 1.5mm, and sintered at 1120°C for 2.5h. The obtained samples were ground, polished, silvered, and polarized in 160°C silicone oil with an electric field of 4kV/mm for 20min. After cooling down, the required ceramic samples were obtained. The comprehensive electrical properties obtained from the test were: d ₃₃ =213pC/N, T _c =395°C, Q _m =356, tanδ=0.002.

Example 2:

Bi ₂ O ₃ , Yb ₂ O ₃ , Pb ₃ O ₄ , TiO ₂ , ZrO ₂ and Nb ₂ O ₅ were weighed according to the molar ratio of (BiYb) _0.06 Pb _0.94 Ti _0.5 Zr _0.44 O ₃ ++0.2mol%Nb, Add water medium to mix ball mill, dry and sieve, pre-fire at 750°C for 2h. Ball mill the pre-fired block, dry it, add 6% PVA to granulate, age for 6 hours, press it into a green body with a diameter of 15mm and a thickness of about 1.5mm after sieving, and sinter at 1150°C for 3 hours to obtain After the sample is ground, polished, and silvered, it is polarized in 160°C silicone oil with an electric field of 4kV/mm for 10 minutes, cooled to 110°C and then polarized for 10 minutes to make a ceramic sample. The comprehensive electrical properties obtained from the test are: d ₃₃ =213pC/N , _Tc =390°C, _Qm =156, tanδ=0.011.

Example 3:

Bi ₂ O ₃ , Yb ₂ O ₃ , Pb ₃ O ₄ , TiO ₂ , ZrO ₂ and Cr ₂ O ₃ were weighed according to the molar ratio of (BiYb) _0.05 Pb _0.95 Ti _0.5 Zr _0.45 O ₃ ++0.2mol%Cr, Add water medium to mix ball mill, dry and sieve, pre-fire at 800°C for 2h. Ball mill the pre-fired block, dry it, add 5% PVA to granulate, age for 6 hours, press it into a green body with a diameter of 15mm and a thickness of about 1.5mm after sieving, and sinter at 1150°C for 3 hours to obtain After the sample is ground, polished, and silvered, it is polarized in 160°C silicone oil with an electric field of 4kV/mm for 10min to prepare a ceramic sample. The comprehensive electrical properties obtained from the test are: d ₃₃ =220pC/N, T _c =401°C, Q _m =180, tanδ=0.001.

Example 4:

Weigh Bi ₂ O ₃ , Yb ₂ O ₃ , Pb ₃ O ₄ , TiO ₂ , ZrO ₂ and Fe ₂ O ₃ according to the stoichiometric ratio of (BiYb) _0.055 Pb _0.945 Ti _0.48 Zr _0.465 O ₃ ++0.2mol%Fe , and add anhydrous ethanol medium to mix and ball mill, so that all the powders are mixed evenly, dry and sieve, and pre-fire at 900°C for 2h. The pre-fired block is fully ball milled, dried and granulated with 5% PVA, aged for 10 hours, sieved and pressed into a green body with a diameter of 12mm and a thickness of about 1.2mm, and sintered at 1180°C for 2.5 h, the required piezoelectric ceramics were prepared. After firing, the samples were ground, polished, silvered, and polarized in 120°C silicone oil with an electric field of 4kV/mm for 20min. The comprehensive electrical properties of the obtained ceramic samples were: d ₃₃ =143pc/N, T _c =370, Q _m = 90, tanδ=0.02. From this example, it can be seen that the various properties of the sample added with Fe are obviously poor, and it is no longer suitable for practical high-temperature applications.

The above embodiments are implemented on the premise of the technical solutions of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the above embodiments.

Table 1 shows the composition, preparation conditions, structure and properties of the prepared piezoelectric ceramic materials obtained in more examples.

Table 1 The composition, structure and performance list of different ceramic samples

(Both are ceramic discs with a diameter of about 12mm and a thickness of about 1mm)

Claims (10)

1. a high temperature piezoceramics, it is characterised in that the chemical structure of general formula of described piezoceramic material is (BiYb)_1-xPb_xTi_yZr_x-yO₃+ zmol%A, wherein A is modifying element, is the ionic radius multivalent metal element that is less than Yb and Ti ionic radius, but does not include ferro element；In described piezoceramic material general structure, x span is 0.91～0.98, and y span is 0.45～0.68, and z span is 0.05～5.

Piezoceramic material the most according to claim 1, it is characterised in that modifying element used includes one or more in Mn, Nb and Cr.

Piezoceramic material the most according to claim 1 and 2, it is characterised in that in described piezoceramic material, z span is 0.08～2.

4. a preparation method for the arbitrary described piezoelectric ceramics of claims 1 to 3, the method comprises the following steps:

(1) by Bi₂O₃、Yb₂O₃、Pb₃O₄、TiO₂、ZrO₂Weighing in molar ratio with oxide or the salt of modifying element, then mixed grinding obtains powder；

(2) powder that step (1) obtained dries, sieve after pre-burning, and block pre-burning obtained is fully ground again；

(3) by step (2) grind obtain powder drying, granulation, be aged, sieve after be pressed into ceramic body；

(4) after binder removal, by ceramic body high temperature sintering in sealed crucible, piezoelectric ceramic body is prepared；

(5) by the piezoelectric ceramic body polishing burnt till, polishing, by after silver electrode, polarization under 100 DEG C～180 DEG C and 3～5kV/mm electric fields.

Method the most according to claim 4, it is characterised in that the oxide of described modifying element includes MnCO₃、Nb₂O₅And Cr₂O₃In one or more.

6. according to the method described in claim 4 or 5, it is characterised in that lapping mode used by step (1) and step (2) is ball milling.

Method the most according to claim 6, it is characterised in that during ball milling, material: abrading-ball: the proportion of liquid spheres grinding media is 1:1～2:0.5～2.

Method the most according to claim 4, it is characterised in that the calcined temperature of step (2) is 700～900 DEG C, burn-in time is 1.5-3 hour.

Method the most according to claim 4, it is characterised in that during step (3) granulation, bonding agent used is the aqueous solution that mass fraction is not more than 6%PVA；Digestion time is not more than 12 hours.

10., according to the method described in claim 4 or 5, it is characterised in that step (4) described sintering temperature is 1050～1280 DEG C, sintering time is 2～5 hours.