JPH0437076A - Piezoelectric porcelain compound - Google Patents

Abstract

PURPOSE:To augment the electromechanical coupling coefficient and the permittivity by a method wherein specific amount of oxide of Mn, Sb and Nb are added to specific composition comprising the compound oxide of Pb, Zr and Ti. CONSTITUTION:As for the title piezoelectric porcelain composition, the composition represented by the shown structural formula is applicable. Within the formula, x,y,z respectively satisfy the following inequalities and equality i.e. 0.42<=x<=0.45, 0.46<=y<=0.49, 0.08<=z<=0.100 and x+y+z=1 while a,b,c respectively satisfy the following equality and inequalities i.e. a=1, 0<=b<=0.45, 0.33<=c<=0.50. When Nb=1, Sb>0.45, the drift in the resonance frequency after temperature cycling is increases. Besides, when Mn<0.33, the drift in the resonance frequency after the temperature cycling is increased. Through these procedures, the title piezoelectric ceramic composition suitable for rudder type filter etc. having high mechanical quality coefficient at high permittivity, minimum loss and high attenuation factor can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a piezoelectric ceramic composition suitable for low-loss, high-attenuation ladder-type filters and the like.

(Prior art) In recent years, with the increase in the amount of communication information such as video signals and audio signals, and the diversification of communication terminals such as car phones and mobile communications, filters with high sensitivity, low loss, and high reliability are required. It is desired to develop a pressure tvt device composition suitable for such a filter.

Conventionally, as this type of piezoelectric ceramic composition, a so-called PZT-based piezoelectric ceramic composition consisting of a composite oxide of lead (Pb), zirconium (Zr), and titanium (Ti) has been used. oxides of tin (Sn) and niobium (Nb) are added as mechanical quality factor (Qm).
) has been proposed in Japanese Patent Publication No. 54-34920 (1988), which has a composition that increases the temperature characteristics of the resonance frequency and reduces changes in the temperature characteristics of the resonance frequency.

In addition, antimony (sb) and tin (S
Japanese Patent Publication No. 54-36756 proposes to improve the dielectric constant (εr) and piezoelectric constant and increase the electromechanical coupling coefficient (Kp) by adding oxide n).

(Problems to be Solved by the Invention) However, although the porcelain disclosed in Japanese Patent Publication No. 54-34920 describes an increase in the mechanical quality factor, there is no improvement in the electromechanical coupling coefficient (Kp), and there is no particular improvement in the electromechanical coupling coefficient (Kp). Although the porcelain of Publication No. 54-36756 mentions improvement in electromechanical coupling coefficient (Kp), there is no mention of mechanical quality coefficient (Qm).

Furthermore, the porcelain of the prior art has a problem in that the resonant frequency changes significantly with respect to temperature changes, which is a practically important characteristic. As a result, when used as a filter for a vehicle-mounted communication device, etc., which undergoes rapid environmental changes, there is a problem in that the set transmission and reception frequency fluctuates due to changes in the temperature inside the vehicle, making stable transmission and reception impossible.

(Objective of the Invention) The object of the present invention is to solve the above-mentioned problems and to provide a novel piezoelectric filter suitable for ladder-type filters, etc., which has a high mechanical quality factor Qm, a large dielectric constant εr, low loss, and high attenuation. To provide porcelain compositions.

(Means for Solving the Problems) As a result of studying the above problems, the inventors have found that:
PZT-based piezoelectric ceramic composition containing Mn, Sb and N
The inventors have discovered that by adding oxide b, it is possible to have a high electromechanical coupling coefficient and to reduce fluctuations (drift) in the resonance frequency before and after temperature cycling, leading to the present invention.

That is, the piezoelectric ceramic composition of the present invention has the following formula (1)% formula %) where X, y, and Z are...(1
)0.42≦X≦0.45 0.46≦y≦0.49 0.08≦2≦0.100 x + y + z =
1, and a, b, and c are 0≦b≦0.45 and 0.33≦C≦0.50 for a=1, and furthermore, in the composition, 3 to 1O of Pb
It is characterized in that atomic % is replaced with at least one selected from Ba, Ca and Sr.

The reason for setting the ratio of each metal element in the ceramic composition of the present invention within the above range is that if the y value is smaller than 0.42, the electromechanical coupling coefficient will be small, and if the y value is larger than 0.45, the resonant frequency after temperature cycling will be small. If the fluctuation (drift) becomes large and the y value is smaller than 0.46, the temperature coefficient of the resonant frequency becomes large, and if the y value is larger than 0.49, the electromechanical coupling coefficient becomes small. Moreover, if the Z value is smaller than 0.08, the sinterability will be poor, and if the Z value is larger than 0.10, the Curie point (Tc) will be low.

Also, in the ratio of Nb, Sb and Mn, Nb is 1
On the other hand, if sb is larger than 0.45, the fa-mid drift after temperature cycling becomes thicker. Also, if Mn is smaller than 0.33, the fa-mid drift after temperature cycling becomes large.

In addition, in order to make the overall valence of Nb, Sn, and Mn, which are the third components, to be 4 on average, the upper limit of Kn was set by setting the Mn amount to 0.5.

The optimum value of the addition amount of Nb5Sb, Mn is given by formula (1), and a
=1 for 0.16≦b≦0.40.0.40≦C≦
It is 0.50.

Further, according to the present invention, by adding oxides of Ha, Ca, and Sr to the piezoelectric ceramic composition described above, the dielectric constant εr can be increased without any adverse effects. The oxides of Ba, Ca, and Sr themselves form A sites in the perovskite crystal structure represented by the above-mentioned formula (1).

According to the present invention, Pb which is the A site in formula (1)
Pb at a rate of 3 to 10 atomic %, especially 3 to 5 atomic % to
Replace part of . If the amount of substitution is less than 3 atomic %, no effect of improving the dielectric constant can be expected, and if it exceeds IO atomic %, the problem of deterioration of heat resistance will occur.

In the present invention, when manufacturing porcelain, a well-known method can be adopted. Specifically, Pbo, T, which forms the above-mentioned composition,
ie,, ZrO,, Nb, 0. ,Sb,D, ,Mn
Metal oxides of constituent metal elements such as 0t are weighed and mixed as raw material powders so that their proportions fall within the above-mentioned range.

At this time, in addition to oxide powder, carbonates, oxoxides, and the like can be used as raw materials. In addition, when preparing PbTf03 and PbZ, the above oxide powders are combined and calcined.
Of course, it is also possible to adjust and mix composite oxide powder such as rO3.

The weighed and mixed powder is formed into a desired shape by press molding, doctor blade method, etc., and then fired.

Firing is performed in an oxidizing atmosphere at 1200 to 1340°C for 2 to 30 minutes.
Do it for 6 hours.

It is desirable that the obtained sintered body be a high-density body with a relative density of 95% or more in order to suppress defective waveforms. A sintered body having a relative density of 97% or more can be obtained by firing in an oxidizing atmosphere at 1200''C2500 to 2000 atmospheres.

The invention will now be explained with the following examples.

(Example) As a starting material, the purity is 99.5% or more and the average particle size is 1.
0-3. Oun's commercially available PbO, TiOz, ZrO,...
NbzO5,5btOs, MnO, BaCOx,
CaCO3 and SrCO3 powders were weighed in the proportions shown in Table 1, wet mixed in a ball mill, dried, and calcined at 1000°C.

The obtained calcined product was wet-pulverized for 24 hours in a ball mill, an organic binder was added thereto, and then it was press-molded into a cylindrical shape with a diameter of 17 mm and a height of 1.5 m+a.

The obtained molded body was heated to 1260 to 1340 in an oxidizing atmosphere.
It was baked at °C for 6 hours.

The sintered body was polished to a diameter of 15 mm and a height of 1 m +++, and silver paste was baked on both end faces. The completed element was immersed in insulating oil at 80°C, and a voltage of 3KV/mm was applied to both end faces.
Polarization was performed by applying a DC voltage of .

After 24 hours of polarization, the characteristics of the device were measured using an impedance analyzer, including electromechanical coupling coefficient (Kp), mechanical quality factor (Qm), and dielectric constant (εr).

The results are shown in Table 1.

All of the samples showed excellent properties, with Kp of 45 or more, Qm of 1800 or more, Sr of 1000 or more, and fa-mid drift within ±0.3. Ba
, Ca, and Sr were able to increase the Sr content.

On the other hand, samples in which the amounts of each of the ceramic compositions added deviated from the ranges had insufficient characteristics, and the object of the present invention could not be achieved.

(Effects of the Invention) As detailed above, the piezoelectric ceramic composition of the present invention can significantly improve the mechanical quality factor by adding Nb-5b-Kn)-based oxide to PZT, and further improve the mechanical quality factor of the piezoelectric ceramic composition of the present invention. By substituting a portion with Ba, Ca, or Sr, the dielectric constant can be improved. As a result, it is possible to provide high selectivity as a low loss type filter especially in the 455 KHz band.

Patent applicant (663) Kyocera Corporation

Claims (2)

[Claims] (1) The following formula Pb{Zr_xTi_y(Nb_aSb_bMn_c)
_z}O_3 In the formula, x, y, z are 0.42≦x≦0.45 0.46≦y≦0.49 0.08≦z≦0.100 x+y+z=1, and a
, b, and c are piezoelectric ceramic compositions where 0≦b≦0.45 and 0.33≦c≦0.50 for a=1. (2) In the composition, 3 to 10 atomic % of Pb is replaced by Ba, C
The piezoelectric ceramic composition according to claim 1, wherein the piezoelectric ceramic composition is substituted with at least one selected from a and Sr.