CN100465131C - A kind of sodium potassium niobate lithium-based lead-free piezoelectric ceramics and preparation method thereof - Google Patents

Abstract

A sodium potassium niobate lithium-based lead-free piezoelectric ceramic and a preparation method thereof belong to the field of green energy materials. The composition of sodium potassium niobate lithium-based ceramics is represented by the non-stoichiometric general formula (Na _a K _b Lic) (Nb _x Ta _y Sb _z )O ₃ or the addition of -nM, where a, b, and c represent the A-site composition Elements, x, y, and z represent the mole fraction of elements at the B site, and the selection range of values is: 0≤a≤1.5, 0≤b≤1.5, 0<c≤1.5, 1<a+b+c≤3, 0<x≤1.5, 0≤y≤1.5, 0≤z≤1.5, 1<(a+b+c)/(x+y+z)≤3 or 0.2<(a+b+c)/(x +y+z)<1, 0<n≤1, M is calcium, copper, manganese, barium, yttrium, strontium, titanium, zirconium, lanthanum, magnesium, aluminum, silicon, iron, cobalt, nickel, silver, tin, At least one of oxides or composite oxides of antimony and tungsten. Using commercial raw materials and traditional ball milling, roasting, atmospheric pressure sintering and other processes, lead-free piezoelectric ceramics of potassium, sodium and lithium niobate with high voltage properties are prepared. The advantage is that it has good ferroelectric performance; the electromechanical coupling coefficient Kp reaches 10-50%.

Description

A kind of sodium potassium niobate lithium-based lead-free piezoelectric ceramics and preparation method thereof

technical field

The invention belongs to the field of environment-friendly energy materials, and in particular provides a potassium-sodium-lithium niobate-based lead-free piezoelectric ceramic material and a preparation method thereof.

Background technique

The widely used piezoelectric ceramic materials are Pb(Ti, Zr)O ₃ (PZT), PbTiO ₃ -PbZrO ₃ -ABO ₃ (ABO ₃ is a composite perovskite ferroelectric) and PbTiO ₃ and other lead-based ceramics. Wherein the mass fraction of lead is about 70%. This kind of ceramics will cause serious damage to human beings and the ecological environment in the process of production, use and disposal, so it is imperative to develop lead-free piezoelectric materials. The lead-free piezoelectric ceramics that have been reported so far include tungsten bronze structure ceramic system, potassium niobate-based ceramic system, bismuth layer structure ceramic system and barium titanate ceramic system, among which niobate lead-free piezoelectric ceramic is the most promising replacement One of the lead-containing piezoelectric ceramic systems. Document 1 (Nature, 2004 Vol 432, p 84-87) in 2004 reported the piezoelectric properties of niobate-based lead-free piezoelectric ceramics co-modified by lithium, tantalum and antimony, and the texture ceramics prepared by template method The piezoelectric constant can reach 416pC/N. But for the sodium potassium niobate ceramics sintered at atmospheric pressure without any modification, according to literature 3 (Applied Physics Letter. 2004, Vol 85, p412), the piezoelectric constant is only 97pC/N. Document 4 (Applied Physics Letter.2005, Vol 59, p241-244) and Document 5 (Applied Physics Letter.2006, Vol 88, p212) reported that the compression of sodium potassium niobate-based ceramics can be effectively improved by adding modifying elements. Electrical properties, literature 7 (Journal of American Society.1962, Vol 45, p209-13) and literature 8 (MaterialsScience Forum.2005, p475-479) reported the use of advanced preparation processes such as hot pressing sintering and discharge plasma sintering to obtain dense ceramic materials with good properties. Through element modification and optimization of the preparation process, the piezoelectric performance of lead-free sodium potassium niobate-based ceramics has been significantly improved, and is constantly approaching the level of practical application. The contents of the published patents in this field are as follows. Patent CN1609047A discloses crystal orientation ceramics and its preparation method. The general formula of the ceramics is: {Li _x (K _1-y Na _y ) _1-x }{Nb _1-zw Ta _z Sb _w }O ₃ , where 0≤x ≤0.2, 0≤y≤1, 0≤z≤0.4, 0≤w≤0.2, x+z+w>0, characterized by adding lithium, tantalum, antimony and other modifying elements based on sodium potassium niobate , and on this basis, it is made into a ceramic material with a textured structure, excluding polycrystalline ceramic materials. Patent CN1810711A discloses a high Curie point sodium potassium niobate lithium-based lead-free piezoelectric ceramic and its preparation method. The general formula of the ceramic can be expressed as: (1-u)[(1-z)(Li _x Na _y K _{1 -xy} )NbO ₃ +zMTiO ₃ ]+uMnO ₂ , where x, y, and z represent the atomic percentages of the corresponding element materials in each component in the compound ion, and the sum of all atoms is 1, 0.01≤x≤0.2, 0.2≤y≤0.7, 0.01≤z≤0.25, 0≤u≤0.05, characterized in that on the basis of sodium potassium lithium niobate, one or more titanates of Mg, Ca, Sr, Ba or oxidation substances are modified. Patent CN1884198A discloses sodium potassium niobate tantalate-based lead-free piezoelectric ceramics and its preparation method, which is characterized in that it is based on sodium potassium niobate tantalate, and the general formula of the base material is: (K _1-x Na _x )(Nb _{1 -y} Ta _y )O ₃ where x=0.1~0.9, y=0.01~0.30), on this basis, add any one or any several of Cu ²⁺ , Sb ⁵⁺ , Sn ⁴⁺ , Li ⁺ modified. Patent CN1511802A discloses a class of multi-element niobate-based lead-free piezoelectric ceramics, and its claimed composition is: (Li _x Na _y K _1-xy )(Nb _1-z R _z )O ₃ or based on this Add one or more LMnO ₃ , where 0<x≤0.3, 0<y<1, 0<(x+y)<1, 0≤z≤0.4, R is Ta or Sb or both The composite ions of L are Y, Er, Ho, Dy, Tm, Lu, Yb, Lu, Nd, Sm rare earth metal elements, and the addition ratio of _LMnO is 0-17wt%, (Li _x Na _y K _1-xy )(Nb _1-z R _z )O ₃ has a proportion of 83-17 wt%. The feature of this patent is based on sodium potassium lithium niobate, first replace Nb with Ta and Sb, and then do rare earth metal element doping. Patent CN1644562A discloses sodium potassium niobate system lead-free piezoelectric ceramics and its preparation method. Although the patent CN1388089A has reported a perovskite structure compound with Na, Li, Nb and O elements as main components, its general formula is: (1-u)[(1-z)Na _1-x Li _x ) _{1- y} K _y ](Nb _1-z Ta _z )O ₃ -nM1M2O ₃ , wherein, 0.02≤x≤0.3, 0≤y≤0.2, 0≤z≤0.2, 0≤n≤0.1, M1 is a divalent metal, M2 is a tetravalent metal, but its additive elements include not only tantalum, but also other metal elements, and the mole fraction of potassium is between 0 and 0.2. The common feature of the patents that have been published so far is that the general formula of the ceramic material is ABO ₃ , and the sum of the mole fractions of atoms at the A site is 1, that is to say, they all belong to the category of stoichiometric ratio. Patent CN1919791A discloses a high-Qm sodium-potassium niobate-based lead-free piezoelectric ceramic and its intermediate frequency resonator, which is characterized in that it is based on sodium-potassium niobate, and its general formula is (Na _x K _1-x+δ ) Nb _1+z O ₃ +wmolCuO, where 0≤x≤1, 0≤δ≤0.1, 0≤z≤0.2, 0≤w≤0.1, and then doped with CuO to achieve high resonance. Although this published patent is currently the only one involving the sum of the atomic mole fractions at the A site including some non-stoichiometric components, it does not contain lithium and its piezoelectric constant is only 90-120.

Contents of the invention

The object of the present invention is to provide a sodium potassium lithium niobate base ceramic with a high piezoelectric constant and a preparation method thereof. The patent aims at the defect of low piezoelectric constant d ₃₃ of niobate-based lead-free piezoelectric ceramics prepared by ordinary sintering methods, and provides a composition of sodium potassium lithium niobate-based lead-free piezoelectric ceramics with high piezoelectric constant Design, the composition involves a non-stoichiometric ratio category, and its piezoelectric constant d ₃₃ is not less than 150pC/N.

The composition of a sodium potassium lithium niobate-based ceramic provided by the present invention can be represented by the general formula (Na _a K _b Li _c )(Nb _x Ta _y Sb _z )O ₃ , where a, b, and c represent the A-site composition Element, x, y, and z represent the mole fraction of the constituent elements at the B site, and the selection range of values is: 0≤a≤1.5, 0≤b≤1.5, 0<c≤1.5, 1<a+b+c≤3, 0<x≤1.5, 0≤y≤1.5, 0≤z≤1.5, 1<(a+b+c)/(x+y+z)≤3 or 0.2<(a+b+c)/(x +y+z)<1.

The present invention also provides a piezoelectric ceramic composed of one or one dopant added on the basis of the above general formula, with the general formula (Na _a K _b Li _c )(Nb _x Ta _y Sb _z )O ₃ - nM means, where 0≤a≤1.5, 0≤b≤1.5, 0<c≤1.5, 1<a+b+c≤3, 0<x≤1.5, 0≤y≤1.5, 0≤z≤1.5, 1<(a+b+c)/(x+y+z)≤3 or 0.2<(a+b+c)/(x+y+z)<1, 0<n≤1, M is calcium, At least one of oxides or composite oxides of copper, manganese, barium, yttrium, strontium, titanium, zirconium, lanthanum, magnesium, aluminum, silicon, iron, cobalt, nickel, silver, tin, antimony and tungsten, n represents M is the mole fraction of the constituent elements.

The preparation method of the present invention is to weigh the raw materials according to the weight percentage according to the non-stoichiometric general formula, and then mix the prepared raw materials with absolute ethanol as the medium by ball milling or vibrating milling, and the time is 1-8 hours , dried to obtain dry powder; roast the dry powder at a temperature of 500-900°C and keep it warm for 1-10 hours to synthesize niobate; put the pre-calcined powder into a φ5-30mm mold for compression molding, and then put it into Sintering in a sintering furnace, in the atmosphere at a temperature of 600-1200°C, heat preservation and sintering for 1-5 hours; apply a silver electrode to a potassium-sodium niobate series piezoelectric ceramic disc, and polarize it in silicone oil, and the polarization temperature is 80 -200℃, the time is 10-60min, the voltage is 1-10kV/mm, and various electrical performance tests are performed after the polarization is completed.

The general formula of the non-stoichiometric ratio in the present invention is: (Na _a K _b Li _c ) (Nb _x Ta _y Sb _z ) O ₃ represents, wherein a, b, c represent A-site constituent elements, x, y, z Indicates the mole fraction of the constituent elements at the B site, and the range of values is: 0≤a≤1.5, 0≤b≤1.5, 0<c≤1.5, 1<a+b+c≤3, 0<x≤1.5, 0 ≤y≤1.5, 0≤z≤1.5, 1<(a+b+c)/(x+y+z)≤3 or 0.2<(a+b+c)/(x+y+z)<1 ; or, (Na _a K _b Li _c )(Nb _x Ta _y Sb _z )O ₃ -nM representation, where 0≤a≤1.5, 0≤b≤1.5, 0<c≤1.5, 1<a+b+ c≤3, 0<x≤1.5, 0≤y≤1.5, 0≤z≤1.5, 1<(a+b+c)/(x+y+z)≤3 or 0.2<(a+b+c )/(x+y+z)<1, 0<n≤1, M is calcium, copper, manganese, barium, yttrium, strontium, titanium, zirconium, lanthanum, magnesium, aluminum, silicon, iron, cobalt, nickel, At least one of oxides or composite oxides of silver, tin, antimony, and tungsten, n represents the mole fraction of M constituent elements.

The multi-element piezoelectric ceramic proposed by the present invention has the following advantages:

(1) Excellent piezoelectric performance, its piezoelectric constant d ₃₃ is not less than 150pC/N;

(2) Good ferroelectric properties, as shown in the hysteresis loop diagram of the piezoelectric ceramic sample in Figure 1;

(3) The electromechanical coupling coefficient Kp reaches 10-50%; it has reached the performance index that can be used in practice.

Description of drawings

Figure 1 is a hysteresis loop diagram.

Detailed ways:

The piezoelectric ceramic sample of the present invention is prepared by a solid-phase sintering process, and the process includes grinding and mixing materials, roasting pre-synthesized niobate, fine grinding, adding a binder, forming, solid-phase sintering, grinding, silvering, polarization, etc. process flow. Specifically: according to the general formula (Na _a K _b Li _c )(Nb _x Ta _y Sb _z )O ₃ -nM, the raw materials are weighed according to the weight percentage and then mixed. Mix the materials in the way of grinding, after 1-8 hours, dry to obtain dry powder; roast the dry powder at a temperature of 500-900°C, keep warm for 1-10 hours, and synthesize niobate; pre-calcine the synthesized powder Put it into a φ5-30mm mold and press it into shape, then put it into a sintering furnace for sintering, and keep it in the air for 1-5 hours at a temperature of 600-1200°C; Coat the potassium-sodium niobate series piezoelectric ceramic disc with baking silver The electrode is polarized in silicone oil, the polarization temperature is 80-200°C, the time is 10-60min, and the voltage is 1-10kV/mm. After the polarization is completed, various electrical performance tests are carried out.

The following examples are given to illustrate the present invention in detail.

2-3 specific examples are given below.

Example 1: First, the raw materials are weighed according to the equation (Na _0.569 Kb _0.485 Li _0.40 )(Nb _0.850 Ta _1..5 )O ₃ and the mass of each substance is: 0.7912g sodium carbonate, 0.9255g potassium carbonate, 0.1255g carbonate Lithium 3.5581g niobium pentoxide, 6.5713g tantalum pentoxide. Put the raw materials into a ball mill jar, add 30ml of absolute ethanol as a medium, ball mill at a speed of 160 rpm for 1 hour, transfer the slurry and dry at 80°C for 8 hours. Then the dried powder was calcined at 500° C. for 10 hours. Put the pre-fired powder into a φ20mm mold and press it into shape. Then put the molded powder into a sintering furnace for sintering, and keep it in the atmosphere for 5 hours at 600°C for sintering. Coat the potassium-sodium niobate-based piezoelectric ceramic disk with a baked silver electrode, and polarize it in silicone oil. During the polarization, the temperature is gradually increased from room temperature to 100°C, and then the time is 10 minutes at 1kV/mm.

Example 2: First, the raw materials are weighed according to the equation (Na _0.716 K _{b 0.630} Li _0.823 )(Nb _0.220 Ta _0.213 Sb _0.421 )O _3. The specific mass of each substance is: 0.2395g sodium carbonate, 0.3722g potassium carbonate, 1.2197g Niobium pentoxide, 2.4293g tantalum pentoxide, 0.1520g lithium carbonate, 2.45126 antimony trioxide. Put the raw materials into a ball mill jar, add 30ml of absolute ethanol as a medium, ball mill at a speed of 160 rpm for 1 hour, transfer the slurry and dry at 80°C for 8 hours. Then the dried powder was calcined at 900° C. for 1 hour. Put the pre-fired powder into a φ5mm mold and press it into shape. Then put the formed powder into a sintering furnace for sintering, and keep it in the air for 5 hours at a temperature of 1200°C. Coat the potassium-sodium niobate-based piezoelectric ceramic disc with a baked silver electrode, and polarize it in silicone oil. During the polarization, the temperature is gradually increased from room temperature to 80°C, and then at 2kV/mm for 10 minutes.

Example 3: First, the raw materials are weighed according to the equation (Na _0.456 K _{b 0.630} Li _0.412 )(Nb _0.360 Ta _0.213 Sb _0.421 )O ₃ -0.045-CaO, the specific mass of each substance is: 0.4295g sodium carbonate, 0.6522g carbonic acid Potassium, 3.1197g niobium pentoxide, 4.7164g tantalum pentoxide, 0.3521g lithium carbonate, 6.3124 antimony trioxide, 0.1211g calcium oxide. Put the raw materials into a ball mill jar, add 30ml of absolute ethanol as a medium, ball mill at a speed of 160 rpm for 8 hours, transfer the slurry and dry at 80°C for 8 hours. Then the dried powder was calcined at 700° C. for 3 hours. Put the pre-fired powder into a φ16mm mold and press it into shape. Then put the formed powder into a sintering furnace for sintering, and keep it in the air for 5 hours at a temperature of 1020°C. Coat the potassium-sodium niobate-based piezoelectric ceramic disk with a baked silver electrode, and conduct polarization in silicone oil. During polarization, the temperature is gradually increased from room temperature to 200°C, and then the time is 60 minutes at 1kV/mm.

Example 4: First, the raw materials are weighed according to the equation (Na _0.463 K _b0.620 Li _0.420 )(Nb _0.126 Ta _0.713 Sb _0.421 )O ₃ -0.036-SrO, the specific mass of each substance is: 0.2395g sodium carbonate, 0.3722g Potassium carbonate, 1.2197g niobium pentoxide, 11.3164g tantalum pentoxide, 0.2525g lithium carbonate, 6.0671 antimony trioxide, 0.3311g strontium oxide. Put the raw materials into a ball mill jar, add 30ml of absolute ethanol as a medium, ball mill at a speed of 160 rpm for 6 hours, transfer the slurry and dry at 80°C for 8 hours. Then the dried powder was calcined at 750° C. for 4 hours. Put the pre-fired powder into a φ30mm mold and press it into shape. Then put the formed powder into a sintering furnace for sintering, and keep it in the air for 3 hours at a temperature of 1040°C. Coat the potassium-sodium niobate-based piezoelectric ceramic disk with a baked silver electrode, and polarize it in silicone oil. During the polarization, the temperature is gradually increased from room temperature to 100°C, and then at 10kV/mm for 20 minutes.

Several preferred embodiments of the present invention are given in the table below. Among them, d ₃₃ , Kp, ε, and tanδ represent piezoelectric constant, electromechanical coupling coefficient, dielectric constant, and dielectric loss, respectively.

Detailed ways:

sample Sintering temperature (℃) a b c x the y z no element d₃₃(pC/N) 1 1050 0.000 1.500 0.010 1.000 0.000 0.000 0.000 none 165 2 1060 0.525 0.485 0.010 0.100 0.000 0.820 0.000 none 191 3 1040 0.569 0.485 0.040 0.850 1.500 0.000 0.000 none 230 4 1070 0.530 0.490 0.055 1.500 0.000 0.000 0.000 none 243 5 1060 0.540 0.490 0.070 0.100 0.000 1.500 0.000 none 187 6 1130 0.550 1.500 0.080 0.140 0.040 1.205 0.000 none 247 7 1040 0.612 0.560 0.021 0.160 0.600 0.600 0.000 none 160 8 970 0.740 0.570 0.640 0.149 0.400 0.101 0.000 none 304 9 1090 0.760 0.580 0.650 0.180 0.210 0.360 0.000 none 210 10 1050 0.800 0.620 0.760 0.200 0.680 0.631 0.000 none 185 11 1130 0.716 0.630 0.823 0.220 0.213 0.421 0.000 none 176 12 900 0.100 0.710 0.954 0.260 0.362 0.325 1.000 Mg 190 13 980 1.100 0.630 1.000 0.360 0.412 0.541 0.450 Ca 178 14 1160 1.200 0.600 1.200 0.950 0.060 0.214 0.692 Sr 216 15 1120 1.500 0.000 1.500 0.160 0.860 0.258 0.250 Ba 203 16 940 0.542 0.531 0.042 0.213 0.080 0.165 0.564 Cu 195 17 1160 1.300 0.501 0.006 0.546 0.094 0.370 0.587 mn 234 18 1130 1.500 0.000 1.400 0.800 0.758 0.140 0.366 Y 212 19 1040 0.055 0.251 0.354 0.945 1.450 0.885 0.450 Ti 248 20 1080 0.015 0.250 0.956 0.150 0.250 1.230 1.000 Zr 173 twenty one 1180 1.500 0.000 1.430 0.160 0.763 0.140 0.680 La 201 twenty two 1000 0.325 0.982 1.215 0.544 0.250 1.032 0.460 Al 186 twenty three 1170 0.256 0.248 1.341 0.135 0.065 0.968 0.853 Si 215

twenty four 980 0.464 0.780 0.896 0.160 0.386 0.352 0.574 Fe 224 25 1130 0.768 0.512 1.500 0.165 0.452 0.481 0.056 co 258 26 1040 0.257 1.156 1.356 0.089 0.847 0.150 0.745 Ni 196 27 1000 0.348 0.257 1.224 0.202 0.460 0.147 0.032 Ag 185 28 1050 1.266 0.000 1.047 0.308 0.068 0.572 0.227 sn 168 29 1090 0.209 0.636 0.350 0.453 0.758 0.142 0.792 Sb 210 30 1180 0.503 0.967 0.706 0.569 0.066 0.459 0.358 W 225

Claims (4)

1, a kind of potassium-sodium niobate lithium radical leadless piezo-electric ceramic with high tension performance is characterized in that, with non-stoichiometric general formula (Na _aK _bLi _c) (Nb _xTa _ySb _z) O ₃Expression, wherein a, b, c represent that A position composition element, x, y, z represent the molar fraction of B position composition element, the range of choice of numerical value is: 0≤a≤1.5,0≤b≤1.5,0＜c≤1.5,1＜a+b+c≤3,0＜x≤1.5,0≤y≤1.5,0≤z≤1.5,1＜(a+b+c)/(x+y+z)≤3 or 0.2＜(a+b+c)/(x+y+z)＜1.

2, according to claim 1 leadless piezoelectric ceramics, it is characterized in that, add one or more hotchpotchs and formed piezoelectric ceramics, with non-stoichiometric general formula (Na _aK _bLi _c) (Nb _xTa _ySb _z) O ₃-nM represents, 0≤a≤1.5,0≤b≤1.5,0＜c≤1.5 wherein, 1＜a+b+c≤3,0＜x≤1.5,0≤y≤1.5,0≤z≤1.5,1＜(a+b+c)/(x+y+z)≤3 or 0.2＜(a+b+c)/(x+y+z)＜1,0＜n≤1, n represents the molar fraction of M component, M is at least a in the oxide compound of calcium, copper, manganese, barium, yttrium, strontium, titanium, zirconium, lanthanum, magnesium, aluminium, silicon, iron, cobalt, nickel, silver, tin, antimony and tungsten or the composite oxides.

3. method for preparing claim 1 or 2 described leadless piezoelectric ceramicss, it is characterized in that, according to the non-stoichiometric general formula with weigh back batching of raw materials by weight, confected materials is that medium carries out batch mixing in the mode of ball milling or vibration with the dehydrated alcohol, time is 1-8 hour, and oven dry obtains dry powder; With the dry powder roasting, maturing temperature 500-900 ℃, be incubated 1-10 hour, carry out the synthetic of niobate; With the compression moulding in the mould of φ 5-30mm of packing into of pre-burning synthetic powder, put sintering in the sintering oven then into, under 600-1200 ℃ of temperature in the atmosphere, heat preservation sintering 1-5 hour; Potassium-sodium niobate series piezoelectric ceramic disk is coated with roasting silver electrode, polarizes in silicone oil, the polarization temperature is 80-200 ℃, and the time is 10-60min, and voltage is 1-10kV/mm, carries out every electrical performance testing after polarization is finished.

4, in accordance with the method for claim 3, it is characterized in that described non-stoichiometric general formula is: (Na _aK _bLi _c) (Nb _xTa _ySb _z) O ₃Expression, wherein a, b, c represent that A position composition element, x, y, z represent the molar fraction of B position composition element, the range of choice of numerical value is: 0≤a≤1.5,0≤b≤1.5,0＜c≤1.5,1＜a+b+c≤3,0＜x≤1.5,0≤y≤1.5,0≤z≤1.5,1＜(a+b+c)/(x+y+z)≤3 or 0.2＜(a+b+c)/(x+y+z)＜1; Perhaps, (NaK _bLic) (Nb _xTa _ySb _z) O ₃-nM represents, 0≤a≤1.5,0≤b≤1.5,0＜c≤1.5 wherein, 1＜a+b+c≤3,0＜x≤1.5,0≤y≤1.5,0≤z≤1.5,1＜(a+b+c)/(x+y+z)≤3 or 0.2＜(a+b+c)/(x+y+z)＜1,0＜n≤1, M is at least a in the oxide compound of calcium, copper, manganese, barium, yttrium, strontium, titanium, zirconium, lanthanum, magnesium, aluminium, silicon, iron, cobalt, nickel, silver, tin, antimony and tungsten or the composite oxides, n represents the molar fraction of M component.

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