阅读说明：本技术 一种铌酸钠钾基压电晶体的制备方法 (Preparation method of potassium-sodium niobate-based piezoelectric crystal ) 是由 黄效 章少华 谢冰 黄生阳 于 2020-11-26 设计创作，主要内容包括：本发明公开了一种铌酸钠钾基压电晶体的制备方法,包括：S1.按照预设摩尔比称取碳酸钠、碳酸钾、氧化铌、氧化铋、碳酸锂及氧化钽；S2.往称取的原料中加入无水乙醇进行球磨,并将研磨后的浆料干燥；S3.将干燥后的料粉置于高温箱式炉中预烧；S4.往预烧完成的粉末中加入聚乙烯醇的水溶液进行研磨并过筛,得到粉末；S5.将制备得到的粉末置于模具中加压制成压片,并将压片放入高温炉中烧结,冷却后取出,制备得到铌酸钠钾基压电单晶。其通过无籽晶固相生长法制备铌酸钠钾基压电晶体,在原料中掺入适量的氧化铋,再利用高温固相法烧结得到陶瓷基的晶体,该制备方法具有低成本的特点。(The invention discloses a preparation method of a potassium sodium niobate-based piezoelectric crystal, which comprises the following steps: s1, weighing sodium carbonate, potassium carbonate, niobium oxide, bismuth oxide, lithium carbonate and tantalum oxide according to a preset molar ratio; s2, adding absolute ethyl alcohol into the weighed raw materials to perform ball milling, and drying the milled slurry; s3, placing the dried material powder in a high-temperature box type furnace for presintering; s4, adding a water solution of polyvinyl alcohol into the pre-sintered powder, grinding and sieving to obtain powder; and S5, placing the prepared powder into a mold, pressing into a pressed sheet, placing the pressed sheet into a high-temperature furnace, sintering, cooling, and taking out to prepare the potassium-sodium niobate-based piezoelectric single crystal. The sodium potassium niobate-based piezoelectric crystal is prepared by a seedless solid phase growth method, a proper amount of bismuth oxide is doped into the raw material, and then the ceramic-based crystal is obtained by sintering by a high-temperature solid phase method.)

1. A method for preparing potassium-sodium niobate based piezoelectric single crystal is characterized by comprising the following steps:

s1, weighing sodium carbonate, potassium carbonate, niobium oxide, bismuth oxide, lithium carbonate and tantalum oxide according to a preset molar ratio;

s2, adding absolute ethyl alcohol into the weighed raw materials to perform ball milling, and drying the milled slurry;

s3, placing the dried powder in a high-temperature box type furnace for presintering;

s4, adding a polyvinyl alcohol aqueous solution into the pre-sintered powder, grinding and sieving to obtain powder;

s5, placing the prepared powder into a die, pressing into a tablet, placing the tablet into a high-temperature furnace for sintering, cooling and taking out to prepare the potassium-sodium niobate-based piezoelectric single crystal.

2. The production method according to claim 1, wherein in step S1, the molar ratio of sodium carbonate, potassium carbonate, niobium oxide and bismuth oxide is 0.45: 0.55: 0.996: 0.004, the molar ratio of lithium carbonate and tantalum oxide is 1:1, and the molar ratio of lithium carbonate and tantalum oxide to the main component is 0.01 to 0.04.

3. The preparation method according to claim 1, wherein in step S2, the raw materials weighed in step S1 are put into a ball mill pot, ball milling seeds and absolute ethyl alcohol are added, and the ball mill pot is subjected to ball milling by a planetary ball mill, wherein the ball milling seeds are agate balls, and the mass ratio of the raw materials to the agate balls to the absolute ethyl alcohol is 1:2: 1.5.

4. The method according to claim 3, wherein in step S2, the ball mill rotates at 400 r/min for 6 h; the drying temperature is 100 ℃ and the drying time is 12 h.

5. The method of claim 1, wherein in step S3, the dried powder is pre-fired by heating the powder to 800 ℃ at a rate of 5 ℃/min in a high temperature box furnace and holding the temperature for 4 hours.

6. The method according to claim 1, wherein in step S4, a small amount of polyvinyl alcohol having a mass concentration of 5% is added, and the sieve is made using an 80-mesh sieve.

7. The method according to claim 1, wherein in step S5, the pressing pressure is 30Mpa gauge pressure, and the pressure is maintained at 10Mpa or less for pressure relief; the temperature is raised to 600 ℃ at the speed of 5 ℃/min in a high temperature furnace and is preserved for 4 hours to remove the glue, and then the temperature is raised to 1100 ℃ at the speed of 5 ℃/min and is preserved for 12 hours to sinter.

Technical Field

The invention relates to the technical field of piezoelectric ceramics, in particular to a preparation method of a potassium sodium niobate-based piezoelectric crystal.

Background

Lead zirconate titanate (PZT) piezoelectric ceramics have monopolized the piezoelectric ceramics industry for more than half a century since their excellent performance characteristics. However, although PZT ceramics have extremely high electrical properties, lead contained therein is a toxic substance and damages the brain and nervous system after entering the human body. If the waste is not properly treated, the ecological environment is greatly damaged, so that the research of a piezoelectric material capable of replacing PZT ceramic is urgent. At present, an important lead-free piezoelectric material is a potassium sodium niobate ceramic material, but the potassium sodium niobate ceramic has low crystallization degree and low piezoelectric constant, so that the potassium sodium niobate ceramic cannot really replace lead zirconate titanate ceramic. By improving the crystallization degree of the potassium sodium niobate, the piezoelectric property of the potassium sodium niobate material can be better improved.

Disclosure of Invention

The invention aims to provide a preparation method of a potassium-sodium niobate-based piezoelectric crystal, which realizes the low-cost preparation of the potassium-sodium niobate-based piezoelectric crystal.

The technical scheme provided by the invention is as follows:

a method for preparing potassium-sodium niobate-based piezoelectric crystals comprises the following steps:

s1, weighing sodium carbonate, potassium carbonate, niobium oxide, bismuth oxide, lithium carbonate and tantalum oxide according to a preset molar ratio;

s2, adding absolute ethyl alcohol into the weighed raw materials to perform ball milling, and drying the milled slurry;

s3, placing the dried powder in a high-temperature box type furnace for presintering;

s4, adding a polyvinyl alcohol aqueous solution into the pre-sintered powder, grinding and sieving to obtain powder;

s5, placing the prepared powder into a die, pressing into a tablet, placing the tablet into a high-temperature furnace for sintering, cooling and taking out to prepare the potassium-sodium niobate-based piezoelectric crystal.

The preparation method of the potassium-sodium niobate-based piezoelectric crystal provided by the invention is characterized in that the potassium-sodium niobate-based piezoelectric crystal is prepared by a seedless solid phase growth method, a proper amount of bismuth oxide is doped into the raw material, and then the ceramic-based crystal is obtained by sintering by a high-temperature solid phase method. The prepared potassium sodium niobate-based piezoelectric crystal has various electrical properties superior to those of corresponding piezoelectric ceramics, and can realize lead-free development.

Drawings

The foregoing features, technical features, advantages and embodiments are further described in the following detailed description of the preferred embodiments, which is to be read in connection with the accompanying drawings.

FIG. 1 is a flow chart of the process for preparing potassium sodium niobate-based piezoelectric crystals of the present invention.

Detailed Description

The essence of the invention is further illustrated below with reference to the figures and examples, but the invention is not limited thereto.

As shown in fig. 1, a flow chart of a method for preparing a potassium sodium niobate-based piezoelectric crystal according to the present invention is shown, and as can be seen from the flow chart, the method comprises:

s1, weighing sodium carbonate, potassium carbonate, niobium oxide, bismuth oxide, lithium carbonate and tantalum oxide according to a preset molar ratio. Specifically, the molar ratio of sodium carbonate, potassium carbonate, niobium oxide and bismuth oxide is 0.45: 0.55: 0.004: 0.996, the molar ratio of lithium carbonate and tantalum oxide is 1:1, and the molar ratio of lithium carbonate and tantalum oxide to the main component is 0.01-0.04.

S2, adding absolute ethyl alcohol into the weighed raw materials, performing ball milling, and drying the milled slurry. Specifically, the raw materials weighed in the step S1 are placed into a ball milling tank, ball milling seeds and absolute ethyl alcohol are added, the ball milling tank is subjected to ball milling by a planetary ball mill, wherein the ball milling seeds adopt agate balls, and the mass ratio of the raw materials to the agate balls to the absolute ethyl alcohol is 1:2: 1.5. The rotating speed of the ball mill is 400 r/min, and the ball milling is carried out for 6 h. And taking out the ball milling tank, pouring out the slurry, and drying the slurry in a constant-temperature drying box at the drying temperature of 100 ℃ for 12 hours.

S3, placing the dried powder in a high-temperature box type furnace for pre-burning. Specifically, the high-temperature box furnace is heated to 800 ℃ at the speed of 5 ℃/min and is kept warm for 4 hours to pre-sinter the dried powder.

S4 an aqueous solution of polyvinyl alcohol is added to the pre-baked powder, and the mixture is ground and sieved to obtain a powder. Specifically, a small amount of 5% by mass polyvinyl alcohol solution was added, and a 80-mesh screen was used for sieving.

S5, placing the prepared powder into a die, pressing into a tablet, placing the tablet into a high-temperature furnace for sintering, cooling and taking out to prepare the potassium-sodium niobate-based piezoelectric crystal. Specifically, the pressing pressure is gauge pressure of 30Mpa, and the pressure is maintained below 10Mpa for pressure relief; the temperature is raised to 600 ℃ at the speed of 5 ℃/min in a high temperature furnace and is preserved for 4 hours to remove the glue, and then the temperature is raised to 1100 ℃ at the speed of 5 ℃/min and is preserved for 12 hours to sinter.

The invention is described in further detail below by way of examples:

example 1:

1) 3.3109g of sodium carbonate, 3.5610g of potassium carbonate, 15.082g of niobium oxide, 0.1057g of bismuth oxide, 0.08634g of lithium carbonate and 0.5112g of tantalum oxide are weighed and poured into a ball milling tank, the niobium oxide, the bismuth oxide, the lithium carbonate and the tantalum oxide are poured into the ball milling tank, and finally the potassium carbonate and the sodium carbonate are poured into the ball milling tank.

2) And placing agate ball mill in the ball milling tank, and pouring absolute ethyl alcohol, wherein the mass ratio of the raw materials, the agate balls and the absolute ethyl alcohol is 1:2: 1.5. And (5) ball-milling the ball-milling tank with a planetary ball mill for 6 hours at the rotating speed of 400 r/min. Taking out the ball milling tank, pouring the slurry into a stainless steel bowl, repeatedly washing agate balls in the ball milling tank for at least 3 times by using absolute ethyl alcohol, and pouring the washed absolute ethyl alcohol into the stainless steel bowl. And (3) placing the stainless steel bowl in a constant-temperature drying oven for drying at the temperature of 100 ℃ for 12 hours. Taking out the stainless steel bowl, pouring the dried powder into a crucible, presintering the crucible in a high-temperature box type furnace at the presintering temperature of 800 ℃ for 4 hours, and finally cooling along with the furnace. Taking out the crucible, pouring the pre-sintered powder into a mortar, adding 1ml of aqueous solution of polyvinyl alcohol with the polyvinyl alcohol concentration of 5%, repeatedly grinding and repeatedly sieving, wherein the sieve is an 80-mesh sieve until the particle size of the powder is reduced to below 80 meshes. 0.6g of the powder is weighed out and poured into a mold. The die cavity is lubricated with a release agent before the powder is poured, and a pressure head is arranged after the powder is poured. And (3) placing the die in a tabletting machine for pressurizing, stopping pressurizing until the gauge pressure is 30Mpa, reducing the gauge pressure to below 10Mpa, releasing the pressure, taking out the tabletting, wherein the tabletting size is 12mm in diameter and 1.5mm in thickness.

3) And putting the pressed sheet into an aluminum oxide crucible, laying a layer of zirconium dioxide powder on the bottom of the crucible, covering the crucible cover, heating to 600 ℃ at the room temperature at the speed of 5 ℃/min, staying for 4 h, heating to 1100 ℃ at the speed of 5 ℃/min, preserving heat for 12 h, and then cooling along with the furnace to obtain the piezoelectric ceramic crystal sample.

4) The piezoelectric constant of the sample was measured with a quasi-static measuring instrument (ZJ-4 AN, institute of Acoustic, national academy of sciences). The measurement results are shown in table 1.

Example 2:

1) 3.2649g of sodium carbonate, 3.5115g of potassium carbonate, 14.8724g of niobium oxide, 0.1042g of bismuth oxide, 0.1290g of lithium carbonate and 0.7640g of tantalum oxide are weighed and poured into a ball milling tank, the niobium oxide, the bismuth oxide, the lithium carbonate and the tantalum oxide are poured into the ball milling tank, and finally the potassium carbonate and the sodium carbonate are poured into the ball milling tank.

2) The five steps of ball milling, drying, presintering, granulating and tabletting are the same as the step (2) in the example 1.

3) The sintering process was the same as in step (3) of example 1.

4) The sample test procedure was the same as in step (4) of example 1.

Example 3:

1) 3.2194g of sodium carbonate, 3.4625g of potassium carbonate, 14.665g of niobium oxide, 0.1027g of bismuth oxide, 0.1714g of lithium carbonate and 1.0149g of tantalum oxide are weighed and poured into a ball milling tank, the niobium oxide, the bismuth oxide, the lithium carbonate and the tantalum oxide are poured into the ball milling tank, and finally the potassium carbonate and the sodium carbonate are poured into the ball milling tank.

2) The five steps of ball milling, drying, presintering, granulating and tabletting are the same as the step (2) in the example 1.

3) The sintering process was the same as in step (3) of example 1.

4) The sample test procedure was the same as in step (4) of example 1.

Table 1: piezoelectric properties of potassium sodium niobate-based piezoelectric crystals prepared in examples 1 to 3:

according to the results, the obtained potassium sodium niobate piezoelectric crystal has high piezoelectric constant, good piezoelectric performance and potential for replacing lead zirconate titanate piezoelectric ceramics.

It should be noted that the above embodiments can be freely combined as necessary. The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.