Background technology
At present, Pb-based lanthanumdoped zirconate titanates (PZT) base ceramic material is still main commercial piezoelectric, but its leaded~65wt-% has than high toxicity, and is bigger to environment and human health risk.
Potassium-sodium niobate in the leadless piezoelectric material material (KNN) base pottery, piezoelectric property good (YasuyoshiSaito, et al.Nature, 2004,432:84-87), be expected to part and substitute the lead base piezoelectric.But alkali metals such as K wherein, Na volatilize easily, and the powder granule degree of conventional solid-state method preparation is bigger, and sintering activity is poor, and high sintering temperature has been aggravated the volatilization of elements such as K, Na, causes pottery to be difficult to densified sintering product.
Chemical method is having many advantages aspect the preparation nano-powder: chemical composition ratio easy to control; Can reach the uniform mixing of molecular level; Sintering temperature is low and can effectively control diameter of particle etc. by regulating sintering temperature.The key that chemical method prepares KNN based ceramic powder body is choosing of niobium source.The ethanol niobium often is selected as the niobium source of chemical method because of its good solubility in organism.(Anirban?Chowdhury,et?al.JNanopart?Res,2010:209-215)。But the ethanol niobium costs an arm and a leg, and very easily hydrolysis, and operating environment is required height, is unfavorable for large-scale production.S.A.O ' the Callaghan of Cambridge University etc. has prepared Na with the ammonium niobium oxalate for the niobium source
0.5K
0.5NbO
3Powder (S.A.O ' Callaghan and K.M.Knowles.MaterialsScience and Technology, 2009,25 (11): 1302-1306).Though ammonium niobium oxalate is low than ethanol niobium price, but still is difficult to obtain, and the diameter of particle that makes is bigger, median size reaches 200nm.The superfine people of the king of Beijing University of Technology is the niobium source with the niobium oxides, and citric acid is that complexing agent has prepared the little lithium sodium kalium niobate powder of grain size (king is superfine.The chemistry journal.2009,67 (3): 203-207), though cost is lower, preparation process is cumbersome, need make the reaction of niobium oxides and potassium hydroxide obtain water-soluble potassium niobate earlier.Therefore how prepare subject matter that potassium-sodium niobate nano-powder will solve and be with the cheap raw material that is easy to get, simply technology obtains the little and uniform powder of particle diameter.
Summary of the invention
The purpose of this invention is to provide a kind of method for preparing potassium-sodium niobate nano-powder.By choosing suitable starting material, significantly reduce cost, simplify production technique.This method also is applicable to other niobate materials of preparation.
The method for preparing potassium-sodium niobate nano-powder comprises following sequential steps:
Step 1: contain the preparation of niobium oxalate solution.A certain amount of oxalic acid is dissolved in distilled water, then the niobium hydroxide powder is added in the oxalic acid solution, 70~95 ℃ are stirred to and dissolve to such an extent that contain niobium oxalate solution A fully; Wherein, niobium hydroxide and oxalic acid mol ratio are 1: 4~1: 14 (especially 1: 8-1: 10);
Step 2: carbonate, oxide compound or the oxyhydroxide of sodium, potassium are pressed Na
0.5K
0.5NbO
3The chemical formula proportioning be dissolved in step 1 preparation contain niobium oxalate solution A, transfer pH value to 1~5 with ammoniacal liquor; Add ethylene glycol then in solution A, ethylene glycol is 1: 1~5: 1 (especially 2: 1~3: 1) by the mol ratio with oxalic acid, make its under 70~95 ℃ of agitation conditions, react yellow solution B;
Step 3: treat that solution B is reacted to thickness and put into loft drier, 90~130 ℃ of dry solid C;
Step 4: pre-burning: solid C processing under 300~400 ℃ was got intermediate product D in 2 hours;
Step 5: calcining: intermediate product D calcining under 500~650 ℃ was got the potassium-sodium niobate powder in 2~5 hours.
Characteristics of the present invention be by adopt niobium hydroxide cheap and easy to get to do the niobium source, oxalic acid is made complexing agent, has significantly reduced cost, has simplified production technique.Utilize method provided by the invention can synthesize high-purity, the uniform potassium-sodium niobate powder of composition, the granule-morphology of prepared powder is similar to cube, particle median size 60-80nm, sintering activity is big, and sintering obtains fine and close leadless piezoelectric ceramics at a lower temperature.
Embodiment
Below by the elaboration of specific embodiment, further specify substantive distinguishing features of the present invention and obvious improvement, but the present invention only is confined to embodiment by no means.
Embodiment 1
In the present embodiment, potassium-sodium niobate nano-powder adopts the sol-gel method preparation, and concrete processing step is as follows:
A) contain the preparation of niobium oxalate solution.A certain amount of oxalic acid is dissolved in distilled water, then the niobium hydroxide powder is added oxalic acid solution, the mol ratio of niobium hydroxide and oxalic acid is 1: 8, and 80 ℃ are stirred to and dissolve to such an extent that contain niobium oxalate solution A fully.
B) yellow soda ash and salt of wormwood are pressed Na
0.5K
0.5NbO
3The chemical formula proportioning be dissolved in solution A, transfer pH value to 2.5 back to add ethylene glycol with ammoniacal liquor, making the mol ratio of ethylene glycol and oxalic acid is 2: 1, make its under 80 ℃ of agitation conditions, react yellow solution B;
C) treating that solution B is reacted to thickness puts into loft drier, 95 ℃ of dry solid C;
D) pre-burning: solid C processing under 350 ℃ was got intermediate product D in 2 hours;
E) calcining: intermediate product D calcining under 500 ℃ was got the potassium-sodium niobate powder in 2 hours.
X-ray diffraction (XRD) analysis revealed, the potassium-sodium niobate powder of method for preparing is pure perovskite structure, crystalline quality good (as Fig. 1); Shown in Fig. 2 transmission electron microscope photo, the potassium-sodium niobate nano-powder granule-morphology that makes is similar to cube, and median size is about 70nm.
Embodiment 2
In the present embodiment, potassium-sodium niobate nano-powder adopts the sol-gel method preparation, and concrete processing step is as follows:
A) contain the preparation of niobium oxalate solution.A certain amount of oxalic acid is dissolved in distilled water, then the niobium hydroxide powder is added oxalic acid solution, the mol ratio of niobium hydroxide and oxalic acid is 1: 8, and 90 ℃ are stirred to and dissolve to such an extent that contain niobium oxalate solution A fully.
B) yellow soda ash, salt of wormwood are pressed Na
0.5K
0.5NbO
3The chemical formula proportioning be dissolved in solution A, transfer pH value to 4 back to add ethylene glycol with ammoniacal liquor, the mol ratio of ethylene glycol and oxalic acid is 2: 1, make its under 90 ℃ of agitation conditions, react yellow solution B;
C) treating that solution B is reacted to thickness puts into loft drier, 115 ℃ of dry white solid C;
D) pre-burning: xerogel C processing under 400 ℃ was got intermediate product D in 2 hours;
E) calcining: intermediate product D calcining under 600 ℃ was got the potassium-sodium niobate powder in 2 hours.
All the other are with embodiment 1
Embodiment 3
In this example, potassium-sodium niobate nano-powder adopts novel sol-gel method preparation, and concrete processing step is as follows:
A) contain the preparation of niobium oxalate solution.A certain amount of oxalic acid is dissolved in distilled water, then the niobium hydroxide powder is added oxalic acid solution, the mol ratio of niobium hydroxide and oxalic acid is 1: 10, and 80 ℃ are stirred to and dissolve to such an extent that contain niobium oxalate solution A fully.
B) yellow soda ash, salt of wormwood are pressed Na
0.5K
0.5NbO
3The chemical formula proportioning be dissolved in solution A, transfer pH value to 2.5 back to add ethylene glycol with ammoniacal liquor, the mol ratio of ethylene glycol and oxalic acid is 3: 1, make its under 80 ℃ of agitation conditions, react yellow solution B;
C) treating that solution B is reacted to thickness puts into loft drier, 115 ℃ of dryings 24 hours white solid C;
D) pre-burning: xerogel C processing under 350 ℃ was got intermediate product D in 2 hours;
E) calcining: intermediate product D calcining under 500 ℃ was got the potassium-sodium niobate powder in 2 hours.
Embodiment 4
In this example, potassium-sodium niobate nano-powder adopts novel sol-gel method preparation, and concrete processing step is as follows:
A) contain the preparation of niobium oxalate solution.A certain amount of oxalic acid is dissolved in distilled water, then the niobium hydroxide powder is added in the oxalic acid solution, the mol ratio of niobium hydroxide and oxalic acid is 1: 8, and 80 ℃ are stirred to and dissolve to such an extent that contain niobium oxalate solution A fully.
B) sodium oxide, potassium oxide are pressed Na
0.5K
0.5NbO
3Composition proportion be dissolved in solution A, transfer pH value to 3 back to add ethylene glycol with ammoniacal liquor, making the mol ratio of ethylene glycol and oxalic acid is 2: 1, make its under 80 ℃ of agitation conditions, react yellow solution B;
C) treating that sol B is reacted to thickness puts into loft drier, 115 ℃ of dry white xerogel C;
D) pre-burning: xerogel C processing under 350 ℃ was got intermediate product D in 2 hours;
E) calcining: intermediate product D calcining under 600 ℃ was got the potassium-sodium niobate powder in 4 hours.Prepared morphology microstructure such as embodiment 1, median size is 80nm.