Patent Application
20150137667
The present disclosure generally relates to a piezoelectricity ceramic material, sinter and method for processing same, piezoelectricity ceramic device with excellent piezoelectricity properties, piezoelectricity ceramic device bimorph and gluing method for improving the temperature stability thereof.
Since the lead zirconate-titanate (PZT) piezoelectricity ceramic was first found in 1954, many countries such as US, Japan, and Holland have made exhaustive studies on the piezoelectricity ceramic system, and with the development of the studies, a series of PZT piezoelectricity ceramic materials with excellent properties have been derived and the application scope of piezoelectricity ceramic materials has also been greatly expanded. Among them, ternary or quaternary system piezoelectricity ceramic based on PZT modified by various elements emerge at the right moment.
In order to obtain high-performance piezoelectricity ceramics, the modified A site (Pb) or B site (Zr, Ti) of Pb(Zr, Ti)O3 are mostly partially replaced and the ratio of Zr/Ti is changed in order to adjust the properties now. It is processed mostly by common solid sintering, that is, blending a precalcined powder and a certain amount of a binder, dry-pressing and then sintering the mixture. The sintering method cannot satisfy the increasingly diversified and complicated requirements of piezoelectricity members and devices, requires high sintering temperature (1200° C.-1300° C.), and is not favorable to reduce cost. Moreover, PbO volatizes seriously during sintering, which not only damages human health and pollutes the environment, but also results in the deviation of actual composition and thus changes the properties. The volatilization of lead also corrodes the heating rod of the sintering machine and reduces the service life of the machine.
With the development of the surface mount technology (SMT), multi-layer piezoelectricity ceramics gain popularity in the market due to their high efficiency, miniaturization, and function integration. This requires that the inner electrode and the ceramic must be co-fired together. The melting point of silver is 961° C. Based on the aforesaid temperature, Ag/Pd alloy is generally used as the co-fired electrode. With the increase of Pd content, the price of Pd will result in a sharp rise in the product cost.
Except for the high piezoelectricity properties, the temperature stability of the ceramic is also required higher and higher in a modern piezoelectricity device. In order to improve the temperature stability of the ceramic, traditional method mainly realized by adjusting the formula of the ceramic, includes the following methods: {circle around (1)} adjust Zr/Ti ratio, a M point with good temperature stability exists around the phase boundary of ceramics. With the transition from a tetragonal to a rhomb, a scope of the temperature stability of the ceramic turning bad rapidly exists. The M point is positioned in the scope and more closing to a side of the tetragonal. {circle around (2)} Mix and modify additive. The additive, such as CoO2, Cr2O3, CeO2, MnO2 and so on, makes the cell structure of ceramics generate distortion. Due to the distortion of the cell structure, the domain wall of the cell structure is beneficial to be redirected and is easier to move, and the stress in the domain is easier to be released. {circle around (3)} Ion-exchange, e.g. use Ni2+, Mn2+, Mg2+ to exchange Pb2+ for generating an oxygen vacancy so as to reduce the size of a cell of ceramics and make the electric domain movement become more difficult, but the temperature stability of the ceramic becomes more better.
Traditional method mainly adjusts the formula of ceramics to improve the temperature stability thereof. Products processed by the traditional method are difficult to be produced and have a long production cycle. In addition, the temperature stability of the product is undesired and does not satisfy the requirement of the development of electronics. With the adjustment of the Zr/Ti ratio of the ceramic, a little change of a M point will result in a big change of the performance of the ceramic. Thus, in order to obtain good performance of the ceramic, the process condition must be controlled strictly.
Many aspects of the embodiment can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The technical solutions in the embodiments of the present disclosure are explicitly described in detail below. Obviously, the described embodiments are only a part of rather than all of the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments occurred to those of ordinary skill in the art without creative work fall within the scope of the present disclosure.
The present disclosure provides a piezoelectricity ceramic material, comprising main components that are represented by a general chemical formula of
Pb(Mn1/3Sb2/3)xZryTizO3+awt % WO3
wherein following conditions are satisfied:
0.02≦x≦0.1, 0.4≦y≦0.6, 0.4≦z≦0.6, and 0.5≦a≦3.
Also, the present disclosure provides a method for processing a piezoelectricity ceramic sinter from the aforesaid piezoelectricity ceramic material, wherein by controlling the particle sizes of the raw material and the precalcined powder, a desired piezoelectricity ceramic sinter is obtained by casting forming; and then a desired piezoelectricity ceramic device is obtained by polarizing the piezoelectricity ceramic sinter in silicone oil with a polarization electric field ranging from 4000 to 6000 V/mm for 20 minutes, and the temperature of the silicone oil is substantially 120° C. Specifically, the method comprises the following steps:
Step S1, material preparation: providing the components of a piezoelectricity ceramic material according to a chemical formula of Pb(Mn1/3Sb2/3)xZryTizO3+awt % WO3 wherein x represents a mole ratio of (Mn1/3Sb2/3) in the chemical formula and 0.02≦x≦0.1, y represents a mole ratio of Zr in the chemical formula and 0.4≦y≦0.6, z represents a mole ratio of Ti in the chemical formula and 0.4≦z≦0.6, awt % represents a weight ratio of WO3 relative to the chemical formula of Pb(Mn1/3Sb2/3)xZryTizO3 and 0.5≦a≦3, and pulverizing the components into a powder, the components comprising Pb3O4, MnCO3, Sb2O3, ZrO2, TiO2, and WO3.
The masses of the components as the raw materials are calculated according to the ratios as set forth in the chemical formula and weighed using a precision electronic balance. The median particle size of the aforesaid components is controlled below 2 μm by raw material selection or ball-mill mixing so as to improve the reactivity of the raw material, and the aforesaid components should be oven-dried substantially 24 hours at 120° C. in an oven.
Step S2, mixing: adding distilled water into the aforesaid processed powder in a mass ratio of substantially 1:1, mixing them for substantially 8 hours, and then oven-drying the mixture.
The processed powder and distilled water are mixed in a ball mill so as to provide a more uniform mixing.
Step S3, calcination: calcining the aforesaid oven-dried product at 800-900° C. for substantially 3 hours to synthesize a calcined product.
Step S4, pulverizetion: pulverizing the aforesaid calcined product to form a mixture and oven-drying the mixture.
In the pulverizetion step, the aforesaid calcined product is pulverized by micro-bead ball mill. The micro-bead ball mill increases the specific surface area of the powder, enhances the activity of the powder, increases the driving force of sintering, and in turn reduces the ceramic sintering temperature.
Step S5, pulping: adding a binder, a plasticizer, a dispersing agent, and a solvent into the aforesaid mixture and mixing them to form a ceramic pulp.
Wherein, the binder, plasticizer, dispersing agent, and solvent added during the pulping are as shown in Table 1 below.
Step S6, forming: debubbling the ceramic pulp and then casting it into a ceramic film.
There are four main methods for forming ceramic film: rolling film forming, casting forming, dry pressing forming, and hydrostatic forming. Rolling film forming is applicable to sheet members; casting forming is applicable to thinner members where the film thickness may be less than 10 μm; dry pressing forming is applicable to block members; hydrostatic forming is applicable to irregular or block members. Apart from hydrostatic forming, all the other forming methods require a binder which is about 3% relative to the weight of the raw material. After forming, it is required to remove the binder. The binder only facilitates forming, but it is a highly reducing substance, which, after forming, shall be removed to prevent it from affecting the sintering quality.
Step S7, laminating: laminating the aforesaid ceramic film to form a laminated product.
Step S8, sintering: firing the laminated product at 1100-1200° C. for substantially 3 hours to form a piezoelectricity ceramic sinter.
For illustrating the present disclosure more detailed, a chemical formula of a piezoelectricity ceramic material, such as Pb(Mn1/3Sb2/3)0.08Zr0.50Ti0.42O3+1 wt % WO3, is provided.
As shown in
The present disclosure further provides a piezoelectricity ceramic device formed by electrode polarizing the aforesaid piezoelectricity ceramic sinter. The piezoelectricity ceramic device is obtained by polarizing the aforesaid piezoelectricity ceramic sinter in silicone oil with a polarization electric field ranging from 4000 to 6000 V/mm for 20 minutes, and the temperature of the silicon oil is substantially 120° C.
The piezoelectricity ceramic device is tested according to the national standard and the piezoelectricity properties are calculated, wherein the test results of the samples are shown in Table 2 in detail.
Referring to
The present disclosure further provides a gluing method for improving the temperature stability of the piezoelectricity ceramic bimorph 1, including the following steps:
Step 1, placing a polarized piezoelectricity ceramic device 10 in greenhouse for at least 24 hours.
Step 2, printing an expoxy adhesive 11 on a surface of one of the placed piezoelectricity ceramic device 10 by screen printing, and then bonding another of the placed piezoelectricity ceramic device 10 with the aforesaid placed piezoelectricity ceramic device 10 in their opposite polarization direction.
Step 3, pressurizedly welding two pieces of the bonded piezoelectricity ceramic devices 10 under room temperature for bonding them completely.
Referring to
For a piezoelectricity vibrator, the resonant frequency fr is:
Wherein l is a length of the piezoelectricity vibrator, p is a density of the piezoelectricity vibrator, and S11E is an elasticity compliance coefficient of the piezoelectricity vibrator. As can be seen, due to the size, density, and elasticity compliance coefficient of the piezoelectricity vibrator are changed with temperature, fr is also changed with temperature. For a piezoelectricity ceramic bimorph, it mainly includes a piezoelectricity ceramic device and an expoxy adhesive. But, because the expoxy adhesive relative to the piezoelectricity ceramic device has a bigger expansion coefficient, the frequency temperature coefficient of the expoxy adhesive relative to that of the piezoelectricity ceramic bimorph is negative. However, the frequency temperature coefficient of the piezoelectricity ceramic device relative to that of the piezoelectricity ceramic bimorph is positive. Therefore, in a piezoelectricity ceramic bimorph, the frequency temperature coefficient of the expoxy adhesive and the frequency temperature coefficient of the piezoelectricity ceramic device are neutralized partially. Consequently, the frequency temperature coefficient of the piezoelectricity ceramic bimorph is near to zero, and the temperature stability of the piezoelectricity ceramic bimorph is improved.
Compared to related art, the products processed by the process method of the present disclosure include the following advantages: a higher temperature stability, a simpler production process, a shorter production cycle, and convenient for mass production.
While the present disclosure has been described with reference to the specific embodiments, the description of the invention is illustrative and is not to be construed as limiting the invention. Various of modifications to the present invention can be made to the exemplary embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201310572270.5 | Nov 2013 | CN | national |
