JPS6074709A - Piezoelectric device - Google Patents

Abstract

PURPOSE:To suppress spurious radiation based on the primary resonance or other spurious radiation effectively by polarizing adjacent ceramics layers in opposite direction mutually and adopting the structure electrodes at both ends are led out externally. CONSTITUTION:Electrodes 15, 16 are formed on upper and lower faces of a piezoelectric ceramics 11 by removing polarization electrodes 13, 14 formed at left and right faces of the piezoelectric ceramics to which internal electrodes 12a-12e are exposed. Thus, a piezoelectric resonator 17 is obtained. The plural electrodes 12a-12e and 15, 16 arranged so as to be overlapped mutually in the resonator 17 constitute electrode groups and ceramics 11a-11d arranged between the electrodes are polarized in opposite direction mutually. Then the electrodes 15, 16 placed at both ends are so constructed that they are led out externally. Through the constitution above, the vibrating displacement in opposite direction to each other is produced among the electrodes adjacent in broadwise direction, and only the specific vibration corresponding to the thickness of the ceramics layer is excited. Thus, other spurious vibrations are suppressed effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [1LLL] This publication relates to pressure flh measurement, in particular to pressure width installation using thickness@vibration.

Piezoelectric resonators, piezoelectric filters, delay filters, etc.
In Ivl, thickness ffl vibration is used in order to use it in a high frequency range of several Ml-12 or more. However, when using thickness longitudinal vibration, it is necessary to suppress the primary resonance that causes spurious vibrations! ! requested.

Therefore, it is conceivable to construct a piezoelectric resonator as schematically shown in FIG. 1.

The piezoelectric resonator 1 shown in FIG. 1 includes a piezoelectric ceramic 2,
It consists of an 11-pole group 3 arranged within a piezoelectric ceramic 2. The electrode group 3 is composed of a plurality of electrodes 3a, 3b, 3c, and 3d arranged so as to overlap each other,
The ceramic layers located between the electrodes are all polarized in the same direction as indicated by arrows P. Electrodes 3a, 3b
, 3c, and 3d, electrodes 3a, 3c are commonly drawn out, and the other electrodes 1111i3b, 3d are commonly drawn out. In the piezoelectric resonator 1 having such a structure,
Since the plurality of electrodes 3a, 3b, 3c, and 3d are arranged sandwiching the polarized ceramic layer, thickness vibration corresponding to the thickness of the ceramic layer is excited. However, since each electrode 38...3d is connected in parallel, ? 1
There is a problem that the impedance decreases exponentially as the number of FLL increases. Therefore, if you try to generate vibrations with higher frequencies, there is a problem that -
) becomes even lower in impedance as the frequency increases, as expressed by the following equation.

Z-1/ω(!-1/2πra where ω: angular frequency, C: capacitance of the entire piezoelectric resonator, f
:Frequency On the other hand, JP-A-58-85614@ discloses a piezoelectric filter for use in a high frequency range. FIG. 2 shows this piezoelectric filter in a schematic 1Eit diagram.

Here, two electrode groups 5.6 are arranged within the piezoelectric ceramic 4. The electrode group 5 constitutes an input side electrode group,
The electrode group 6 constitutes an output side electrode group. Each electrical connector 5, 6 is arranged so that a plurality of them overlap each other! The N-shaped ceramic layers are each polarized in opposite directions as shown by the arrows. In each electrode group 5゜6, two electrodes e15a located on both sides near the piezoelectric ceramic surface
, 5d, 6a, and 6d are connected to input and output terminals, respectively. By having such a W4 structure, a piezoelectric filter that can effectively suppress spurious vibrations based on primary resonance has been achieved. However, in the conventional piezoelectric filter shown in FIG. 2, when vibration is transmitted from the input side electrode group 5 to the output side electrode group 6, the displacement direction is changed twice, so the efficiency is extremely low. Ta. Another drawback is that unnecessary Wc spurious occurs in the output waveform due to lateral displacement, that is, lateral effect.

11L1 Therefore, it is an object of the present invention to overcome the above-mentioned drawbacks and to
An object of the present invention is to provide a piezoelectric device that can effectively suppress spurious waves based on primary resonance or other unnecessary vibration spurious waves, and that exhibits a small drop in impedance even when using higher-order mode vibrations. .

1 discharge m To summarize, the present invention includes an electrode iY consisting of a plurality of electrodes arranged so as to overlap each other, and each electrode group of electrodes iY. !
! a plurality of ceramic layers arranged between the electrodes, each adjacent ceramic layer being polarized in opposite directions,
The piezoelectric device is a piezoelectric device in which the electrode located at the position ffl'l of the electrode group is drawn out to the outside.

Other features of this invention will become clear from the following description of embodiments with reference to the drawings.

111L Figure 3 shows piezoelectric ceramics used to construct the ■electrical resonator according to the first embodiment of the present invention; t'+7!
This is a diagram g. The piezoelectric ceramic 11 is obtained by applying a paste for internal W1 pole to a large number of ceramic green sheets and sintering the paste. Examples of piezoelectric ceramic materials include lead titanium zirconate, lead titanate,
Single-component systems such as barium titanate systems, multi-component systems, or systems with additives added thereto are used. Further, as the paste for the internal W1 electrode, for example, palladium, silver-palladium alloy, or other high melting point metals or alloys may be used. In this example, a piezoelectric ceramic material having a composition of Pbo, 5rLaa4TiOs +0.5% by weight Mn02 is used. In order to obtain a ceramic green sheet, a binder was added to the temporary phosphorus powder of the above-mentioned composition and mixed, and a sheet was formed using a doctor blade method. A palladium paste for internal m-poles was printed and coated on the obtained ceramic green sheet, and then pressure bonded and subjected to II8 measurement at 1200° C. and 2FI# threshold to obtain piezoelectric ceramic 11. In addition, the internal electrode is
A plurality of electrodes 12a are arranged so as to overlap each other.
...12e, which are exposed alternately on the left and right sides of the piezoelectric ceramic 11. Next, polarization electrodes 13 and 14 were formed on the left and right side surfaces of the piezoelectric ceramic 11 where the internal electrodes 12a...12e were exposed, and a voltage was applied to perform polarization treatment. As is clear from the arrows in Figure 3, 6 overs @
The ceramic layer existing between 12B...12e is w4
The adjacent layers are polarized in opposite directions.

Next, the polarization electrode 13.1/I is removed and electrodes 15.1 (3) are formed on the upper and lower surfaces of the rEW1 ceramic 11, as shown in the perspective view in FIG. , a piezoelectric resonator 17 as a first embodiment of the present invention is shown. , as is clear from FIG. 4, the piezoelectric resonator 17
Now, the l! which are arranged so as to overlap each other! number [1
12a...12e and 15+16 constitute an electric Ti group, and the ceramic layers arranged between the m poles are polarized in mutually opposite directions. The electrodes 15 and 16 located at both ends are drawn out to the outside. Therefore, when a voltage is applied from the electrodes 15 and 16, the piezoelectric resonator 17 is excited. By the way, pressure ffi co-supplant 17
In this case, since the ceramic layers 11a...11d between the plurality of electrodes 12+...1213 are polarized in mutually opposite directions, the ff% dynamic displacement in mutually opposite directions between the W1 blocks adjacent to each other in the thickness direction occurs, and a specific WII9! corresponding to the thickness of the ceramic layer occurs. only can be excited.

Therefore, other spurious vibrations can be effectively suppressed. Moreover, unlike the conventional resonator 1 shown in FIG. 1, all of the input and output electrodes are not connected in parallel.

There is no drop in impedance. In other words, even if the structure has an increased number of electrodes for the purpose of higher-order mode resonance, impedance does not decrease, and impedance matching with an external circuit can be easily achieved.

FIG. 7 shows the impedance-frequency characteristics of the piezoelectric resonator 11 of the embodiment shown in FIG. 4. As is clear from FIG. 7, it can be seen that a vibration mode in which almost no spurious components occur is realized.

FIG. 5 is a perspective view showing piezoelectric ceramics used in a piezoelectric filter as a second embodiment of the present invention. Here, a plurality of WINs 22a-22 are included in the piezoelectric ceramic 21.
e, 23a-=23a are formed as internal electrodes. Such a U4 piezoelectric ceramic 21 is manufactured and assembled in the same manner as the piezoelectric ceramic 11 shown in FIG. 3. Next, the internal electrodes 22a...22e, 23a...
Polarization electrodes 24 and 25 are formed on the left and right sides of the piezoelectric ceramic 21 on which the electrodes 23e are formed, and a polarization process is performed. Due to the polarization process, as shown in FIG.
- In the ceramic layers between 22e, 23a, . . . , 230, adjacent layers are polarized in mutually opposite directions. Next, ffff 126 and 27 are formed on the upper and lower surfaces of the piezoelectric ceramic 21. Also electrodes 26.27. Is each B formed inside? ! Number of electrodes 22a...22e, 23B...
・It overlaps in parallel with 23e. Therefore, the electrode 26 and the electrodes 22a to 22Q form one electrode group, and the electrodes 4h 23a to 23e and the electrode 2
7 constitutes the other electrode group. Next, cut off the polarization voltage L @ 25 + 26 used for polarization process by rpJ
Alternatively, it is removed by polishing or the like, and external electrodes 28 and 29 for drawing out the N electrode 228 and the electrode 23a to the outside are formed on one side of the piezoelectric ceramic 2'1. In this way, in the embodiment shown in FIG. 6, in the electrode group arranged above, the electrodes tI! 26
．． 22e is connected to the outside and similarly placed below.
The R electrode group 1v pole 23at3 and the tfI pole 27 are connected to the outside. , two words? ! It is possible to use any of the electrode groups as the input side W1 electrode, but now the upper f! !
If the polar liver is the input side electrode group, electric@26 and electric tll
A voltage is applied from i22e. As a result, vibrations in the thickness root direction are excited by the upper electricity 1i1i snoring, and this vibration propagates within the piezoelectric ceramic 21 and is transmitted to the lower electrode group, and the output is transmitted to the electrodes 27 and ffl! 23a. Therefore, it is understood that since the displacement direction is not converted as in the conventional ceramic filter shown in FIG. 2, a ceramic filter with efficiency of 1q can be realized. Similarly, unnecessary vibrations due to lateral effects are not generated, so
It can be seen that the spurious level is also extremely low. moreover,
A plurality of N poles 26, 228...22 constituting each electrode group
e, 27, 23a...23e, only 27 of each electrode group is drawn out to the outside, so the first
As in the conventional resonator shown in the figure, each electrode is connected in parallel.
It's not something that can be done. Therefore, even when the number of electrodes is increased and a higher-order vibration mode is used, a sudden drop in impedance can be avoided, and problems with impedance matching with an external Il device do not occur. In addition, in each of the electrodes 26.22a to 22e and the electrodes 26.22a to 22e and
3a to 236.27 are confined within the bulk centered on the mutually overlapping portions. Therefore, the side surfaces of the piezoelectric ceramic 11 can be fixed, and there are also advantages in that it can be easily made into a chip component.

FIG. 8 shows the attenuation-frequency characteristics of the piezoelectric filter of the embodiment shown in FIG. 6. In addition, the input side electrode group and the output
The number n of electrode pairs in the side electrode group is 2n+1-10, so n-4.5.

Furthermore, in the actual wl&fN shown in FIG. 6, the pass frequency band can be changed without changing the ceramic material. That is, by changing the thickness of the green sea 1- when forming the piezoelectric ceramic 21, the distance between each electrode can be changed, and thereby the circumference 1 of the sound wave that can pass through can be changed. It is possible to vary the number.

In the embodiment shown in FIG. 6, the input side and output #
! Although no other internal electrodes were formed in one electrode group, one or more internal electrodes may be formed in each tW electrode group instead. FIG. 9 is a perspective view showing an example of such a piezoelectric filter. In the figure, 30 is an internal W1 pole formed between the electrode groups.

Therefore, piezoelectric ceramics may be prepared in which a large number of internal electrodes are arranged so as to overlap in parallel, and some of them may be used to form the electrode group 2111. That is, an electrode group can be constructed by connecting two electrodes including a plurality of ceramic layers partitioned by an internal TSRM to the outside. Also, the internal power I! shown in FIG.
If s30 is grounded, the stray capacity can be reduced.

In addition, by increasing the distance between the electric II groups formed above and below in the embodiment shown in the sixth factor,
It is extremely easy to lengthen the delay time, and therefore it is also possible to use it as a delay element.

Furthermore, in order to suppress the reflection of the excited bulk waves at the end faces (for example, ftfl126 and 27 are formed in the figure W16), the end faces are set at a position away from each m-wavelength, and the wavelength length or ty in each electrode group
Spurious noise can be reduced by forming irregularities on this end face that are about the same or larger than the distance between tm, or by making the end face oblique to each electrode group, or by forming a damping material on the end face. can do.

11 As described above, according to the present invention, the electrodes are made up of a plurality of electrodes arranged so as to intertwine with each other. ! ! Oke lIY and
The electric power of this electrode group! The impedance can be lowered by having a plurality of ceramic layers arranged at jlII, each adjacent ceramic layer is polarized in opposite directions, and has fRyll in which the electrodes at both ends are drawn out to the outside. It is possible to obtain a piezoelectric stomach that can utilize high-frequency vibration without any noise and can effectively suppress other unnecessary vibrations. Therefore, in the resonator, high frequency vibration can be obtained without causing impedance matching problems. Furthermore, when applied to filters or delay lines, the filters and delay lines can be highly efficient and have a low spurious level.

[Brief explanation of the drawing]

FIG. 111 is a schematic front view showing an example of a conventional ceramic resonator. FIG. 2 is a schematic front view of a conventional ceramic filter. FIG. 3 is a perspective view showing piezoelectric ceramics used in one embodiment of the present invention. Fourth
This figure is a perspective view showing a resonator according to an embodiment of the present invention constructed using the piezoelectric ceramic shown in FIG. 3. Fifth
The figure is a perspective view showing piezoelectric ceramics used in another embodiment of the invention. FIG. 6 is a perspective view showing a piezoelectric filter as another embodiment of the present invention constructed using the piezoelectric ceramic shown in FIG. 5. FIG. 7 is a diagram showing the impedance-frequency characteristics of the resonator of the embodiment shown in FIG. Figure 8 is similar to Figure 6 (
It is a figure which shows the attenuation amount-frequency characteristic of the piezoelectric filter of the example shown. FIG. 9 is a perspective view showing another embodiment of the piezoelectric filter. 11-...piezoelectric ceramics, 12a, 12b,
12C, 12d, 12e, 15.16... electrode, 21
...Piezoelectric ceramics, 22a, 22b, 220
．． 22dl 228.23al 23bl 23C,2
3d. 23e, 26.27...WleA. Patent applicant: Murata Manufacturing Co., Ltd. Figure 7 Figure 2 Figure 3 1 P, 12d Figure 7 Circumference (barrel Hx) 10 1 Teo number (to MH)

Claims (2)

[Claims] (1) An electrode group consisting of a plurality of electrodes arranged so as to overlap each other, and a plurality of ceramic layers arranged between the plurality of electrodes, wherein the adjacent ceramic layers are polarized in mutually opposite directions. and the electrode located at F'[ of the electrode group is drawn out to the outside. (2) The electrode group includes an input side electrode group and an output 1l, which are provided so as to overlap in the thickness direction of the ceramic layer.
IIN pole group. ! Device.