CN101219897A - Sol-gel synthesis method of lead-free piezoelectric ceramic lithium sodium potassium niobate nanopowder - Google Patents

Abstract

The invention belongs to the technical field of preparation of piezoelectric ceramic materials. At present, the commercial piezoelectric ceramics are still based on lead zirconate titanate-based ceramics, which cause great damage to the environment. The steps of the present invention: mix niobium pentoxide and potassium pyrosulfate in a molar ratio of 1:8, and dissolve the product obtained by calcination at 280-320°C for 1-2 hours in oxalic acid solution to adjust the pH value to 2-3 to obtain a white precipitate; centrifuge Precipitate and dissolve in oxalic acid solution, and get a clear and transparent niobium-containing oxalic acid solution A after stirring; adjust the solution A to a pH value of 10-11, and centrifuge to obtain a white precipitate B; press the composition ratio of piezoelectric ceramic lithium sodium potassium niobate , dissolving lithium carbonate, sodium carbonate and potassium carbonate in acetic acid to prepare a solution, adding the solution and precipitate B to an aqueous citric acid solution with a concentration of 8-10mol/L, and stirring to obtain a light yellow transparent sol C; 80-120 Drying at ℃ for 48 hours to obtain transparent xerogel D; treating at 300-400℃ for 2 hours to remove organic matter to obtain intermediate product E; calcining at 500-600℃ for 2-8 hours. The powder particle size distribution range of the invention is narrow, the composition is uniform, and the cost is reduced.

Description

Sol-gel synthesis method of lead-free piezoelectric ceramic lithium sodium potassium niobate nanopowder

technical field

The invention relates to a sol-gel synthesis method of lead-free piezoelectric ceramic lithium sodium potassium niobate nanopowder, which belongs to the technical field of piezoelectric ceramic material preparation.

Background technique

At present, the commercial piezoelectric ceramics are still based on lead zirconate titanate (Pb(Zr,Ti)O3, abbreviated as PZT) based ceramics. However, the main raw material of PZT-based ceramics is PbO, which has high toxicity and will cause great damage to human health and the environment during production and recycling.

Lead-free piezoelectric ceramic lithium sodium potassium niobate ((Li0.06Na0.47K0.47)NbO3, abbreviated as LNKN) has attracted widespread attention due to its excellent piezoelectric properties and is considered to be the best choice for PZT-based piezoelectric ceramics. possible substitutes. At present, the synthesis of potassium lithium niobate piezoelectric ceramic powder generally adopts the traditional solid-phase method (references: Guo Y, Kakimoto K, Ohsato H, "Phase transitional behavior and piezoelectric properties ofNa0.5K0.5NbO3-LiNbO3 ceramics" [J ].AppliedPhysics Letters, 2004,85 (18): 4121-4123), the required calcination temperature of this method is higher, and the obtained powder particles are coarse, it is difficult to meet the requirements of high-power multilayer piezoelectric devices for ultrafine powder ( nanoscale) requirements. At the same time, the powder synthesized by the traditional solid-state method has serious agglomeration and low sintering activity. Generally, high temperature above 1000°C is required for ceramic sintering. At high temperature, K and Na volatilize seriously, deteriorating the performance of ceramics.

The sol-gel method is an important chemical method for the preparation of ultrafine (nano) powders, which shows many advantages over the traditional solid-phase method, including accurate composition control, low crystallization temperature and molecular level due to the mixing of liquid phase precursors. good uniformity etc. So far, there is no report on the preparation of lead-free piezoelectric ceramic lithium sodium potassium niobate powder by sol-gel method. The key to the preparation of niobate powder by sol-gel method is the selection of niobium source. Because niobium ethanol (Nb(OC2H5)5) has good solubility, it is often used as a sol-gel method to prepare lead-based niobate ceramic powder. (such as: lead magnesium niobate-lead titanate (PMN-PT), lead niobate nickelate (PNN), etc.) niobium source (references: ZHAI J W, SHEN B, ZHANG L Y, et a1."Preparation and dielectric properties by sol-gel derived PMN-PT powder and ceramic” [J]. Material Chemistry and Physics, 2000, 64(1): 1-4). However, niobium ethanol is expensive, easily hydrolyzed and needs to be stored under special conditions, and the operation is cumbersome, which limits the industrialization of niobate powder prepared by sol-gel method.

Contents of the invention

The purpose of the present invention is to provide a sol-gel synthesis of lead-free piezoelectric ceramic lithium sodium potassium niobate nanopowder on the basis of converting niobium pentoxide (Nb2O5) into soluble niobium salt as a substitute for niobium ethanol method.

The sol-gel synthesis method of lead-free piezoelectric ceramic lithium sodium potassium niobate nanopowder adopted in the present invention is characterized in that: comprising the following process steps:

(1) The product obtained by mixing niobium pentoxide and potassium pyrosulfate in a molar ratio of 1:8 and calcining at 280-320°C for 1-2h is dissolved in oxalic acid solution; then titrate the pH value to 2-3 with nitric acid to obtain white Precipitation; the white precipitate obtained by centrifugation is dissolved in oxalic acid solution, and after stirring, a clear and transparent niobium-containing oxalic acid solution A is obtained;

(2) Titrate the niobium-containing oxalic acid solution A obtained in step 1 with ammonia water to a pH value of 10-11, and obtain a white precipitate B through centrifugation and deionized water washing;

(3) by piezoelectric ceramic lithium sodium potassium niobate (Li0.06Na0.47K0.47) NbO Composition ratio, lithium carbonate, sodium carbonate and salt of wormwood are dissolved in acetic acid and make solution, and this solution obtains in step 2 The white precipitate B was added to the citric acid aqueous solution with a concentration of 8-10mol/L at the same time, and stirred to obtain a light yellow transparent sol C;

(4) Dry the above-mentioned transparent sol C at 80-120° C. for 48 hours to obtain a transparent xerogel D;

(5) Treat the xerogel D obtained above at 300-400°C for 2 hours to remove organic matter, and obtain the intermediate product E;

(6) Calcining the intermediate product E obtained above at 500-600° C. for 2-8 hours.

The present invention uses cheaper and easier to obtain niobium pentoxide to replace niobium ethanol, and obtains niobium-containing oxalic acid solution through a simple chemical conversion process, thereby greatly reducing the production of lead-free niobate powder prepared by sol-gel method cost. The method provided by the invention can be used to synthesize high-purity, superfine lithium sodium potassium niobate powder, the particle size of the powder is between 20 and 60nm, the particle shape is approximately cubic, the size distribution range is narrow, and the composition uniform. Compared with the solid-phase method, the production process of the present invention is simple, the synthesis temperature is reduced, and the obtained product has a uniform particle diameter of nanometer scale. The powder has high sintering activity and meets the requirement of superfine powder (nanoscale) for the preparation of high-power multilayer piezoelectric devices.

Description of drawings

The powder X-ray diffraction (XRD) pattern of different products of Fig. 1. The instrument used was a Bruker D-8 Advance powder diffractometer (Cu Kα radiation, λ=1.5406 Å). Wherein, the curves a-h are respectively the XRD patterns of the lithium sodium potassium niobate powder obtained according to Examples 1-8.

Fig. 2 is the transmission electron micrograph and diffraction pattern of lithium sodium potassium niobate powder obtained according to embodiment 1. The instrument used is a JEM-2010 transmission electron microscope.

Detailed ways

The substantive characteristics and remarkable advantages of the present invention are further clarified by the following examples, and the present invention is by no means limited to the stated examples.

Example 1

(1) The product obtained by mixing niobium pentoxide and potassium pyrosulfate in a molar ratio of 1:8 and calcining at 300°C for 2 hours was dissolved in deionized water; then the pH value was titrated to 2 with nitric acid to obtain a white precipitate; the obtained product was centrifuged The white precipitate is dissolved in oxalic acid solution, and after stirring, a clear and transparent niobium-containing oxalic acid solution A is obtained;

(2) Titrate the niobium-containing oxalic acid solution A obtained in step 1 with ammonia water to a pH value of 10, and obtain a white precipitate B through centrifugation and deionized water washing;

(3) press piezoelectric ceramic lithium sodium potassium niobate (Li0.06Na0.47K0.47) NbO Composition ratio, lithium carbonate, sodium carbonate and salt of wormwood are dissolved in acetic acid and make solution, this solution and step 2 obtain The white precipitate B was added to the citric acid aqueous solution with a concentration of 8-10mol/L at the same time, and stirred to obtain a light yellow transparent sol C;

(4) drying the above-mentioned transparent sol C at 80° C. for 48 hours to obtain a transparent xerogel D;

(5) Treat the xerogel D obtained above at 300°C for 2 hours to remove organic matter, and obtain the intermediate product E;

(6) Calcining the intermediate product E obtained above at 500° C. for 5 h to obtain ceramic powder a.

Experiments show that the obtained lithium sodium potassium niobate powder has a pure perovskite structure, and has a uniform size and approximately cubic particle shape, with an average grain diameter of 20nm. The powders obtained in the remaining examples all have a pure perovskite phase structure and similar particle morphology, and the average grain diameters are all nanoscale, about 20-60nm.

Example 2

Mix niobium pentoxide and potassium pyrosulfate at a molar ratio of 1:8 and calcinate at 280°C for 1 hour to dissolve in deionized water; then titrate the pH value to 3 with nitric acid; Calcination 2h, all the other conditions are the same as in Example 1. Prepare ceramic powder b. The powder X-ray diffraction pattern of product b is shown in Figure 1.

Example 3

The product obtained by mixing niobium pentoxide and potassium pyrosulfate at a molar ratio of 1:8 and calcining at 320°C for 2 h was dissolved in deionized water; the niobium-containing oxalic acid solution A was titrated with ammonia water to a pH value of 11; the transparent sol C was Dry at 120°C for 48 hours to obtain a transparent xerogel D; the intermediate product E obtained above was calcined at 600°C for 5 hours, and the rest of the conditions were the same as in Example 1. Prepare ceramic powder c. The powder X-ray diffraction pattern of product c is shown in Figure 1.

Example 4

Lithium carbonate, sodium carbonate and potassium carbonate that meet the piezoelectric ceramic lithium sodium niobate (Li0.06Na0.47K0.47) NbO3 composition ratio are dissolved in acetic acid to prepare a solution, and the solution is added to the white precipitate B at the same time In an aqueous citric acid solution with a concentration of 10 mol/L; the transparent sol C was dried at 100° C. for 48 hours to obtain a transparent xerogel D, and the rest of the conditions were the same as in Example 1. Prepared ceramic powder d. The powder X-ray diffraction pattern of product d is shown in Figure 1.

Example 5

The xerogel D was treated at 350°C for 2h to remove organic matter; the intermediate product E was calcined at 550°C for 2h, and the other conditions were the same as in Example 4. Prepared ceramic powder e. The powder X-ray diffraction pattern of product e is shown in Figure 1.

Example 6

Dry gel D was treated at 400°C for 2h to remove organic matter; intermediate product E was calcined at 600°C for 8h, and the other conditions were the same as in Example 4. Prepare ceramic powder f. The powder X-ray diffraction pattern of product f is shown in Figure 1.

Claims (1)

1. a sol-gel synthesis method of lead-free piezoelectric ceramic lithium sodium potassium niobate nanopowder, is characterized in that, comprises the following steps: 1) The product obtained by mixing niobium pentoxide and potassium pyrosulfate at a molar ratio of 1:8 and calcining at 280-320°C for 1-2 hours is dissolved in oxalic acid solution; then titrate the pH value to 2-3 with nitric acid to obtain a white precipitate The white precipitate obtained by centrifugation is dissolved in oxalic acid solution, and after stirring, a clear and transparent niobium-containing oxalic acid solution A is obtained; 2) Titrate the niobium-containing oxalic acid solution A obtained in step 1) with ammonia water to a pH value of 10-11, and obtain a white precipitate B by centrifuging and washing with deionized water; 3) According to the distribution ratio of piezoelectric ceramic lithium sodium potassium niobate, lithium carbonate, sodium carbonate and potassium carbonate are dissolved in acetic acid to prepare a solution, and the solution and the white precipitate B obtained in step 2) are added to a concentration of 8-10mol/L citric acid aqueous solution, stirred to obtain light yellow transparent sol C; 4) Dry the above-mentioned transparent sol C at 80-120° C. for 48 hours to obtain a transparent xerogel D; 5) Treat the dry gel D obtained above at 300-400°C for 2 hours to remove organic matter, and obtain the intermediate product E; 6) Calcining the intermediate product E obtained above at 500-600° C. for 2-8 hours.

Images