Unleaded piezoelectric ceramic composition, piezoelectric element using same, device, and method for manufacturing unleaded piezoelectric ceramic composition

Patent metadata

Field	Value
Publication number	US-9938197-B2
Application number	US-201414780235-A
Country	US
Kind code	B2
Filing date	Mar 11, 2014
Priority date	Mar 29, 2013
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A lead-free piezoelectric ceramic composition includes a first crystal phase made of an alkali niobate/tantalate type perovskite oxide having piezoelectric properties, and a second crystal phase made of an M-Ti—O spinel compound (where the element M is a monovalent to quadrivalent element).

First claim

The invention claimed is:

1. A lead-free piezoelectric ceramic composition, comprising:
a main phase comprising a first crystal phase comprising an alkali niobate/tantalate type perovskite oxide having piezoelectric properties; and
a subphase comprising a second crystal phase comprising an M-Ti—O spinel compound (where the element M is a monovalent to quadrivalent element).

2. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein the element M comprises at least one metallic element selected from the group consisting of Li, Mg, Al, Sc, Cr, Mn, Fe, Co, Ni, Zn, Ga, Y, and Zr.

3. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein the M-Ti—O spinel compound is represented by a compositional formula: M x TiO y (where the coefficients x and y are relative values when a content of Ti is taken as 1), and
wherein the coefficient x satisfies 0.5≤x≤5.0.

4. The lead-free piezoelectric ceramic composition according to claim 3 ,
wherein the coefficient y satisfies 2≤y≤8.

5. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein the subphase fills a hole formed in the main phase.

6. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein the contained rate of the second crystal phase in the lead-free piezoelectric ceramic composition is any one of:
(i) 0.5 vol % to 5.0 vol %;
(ii) 0.5 vol % to 2.5 vol %; and
(iii) 1.0 vol % to 2.0 vol %.

7. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein the M-Ti—O spinel compound comprises two or more metallic elements as the element M.

8. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein the subphase comprises a third crystal phase in addition to the second crystal phase, the third crystal phase comprising an A 3 B 5 O 15 type compound (where the element A is a monovalent to divalent metal, and the element B is a divalent to pentavalent metal).

9. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein a volume rate of the second crystal phase is 50% or more when the entire subphase is taken as 100%.

10. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein the alkali niobate/tantalate type perovskite oxide of the first crystal phase comprises an alkali earth metal.

11. The lead-free piezoelectric ceramic composition according to claim 10 ,
wherein the alkali niobate/tantalate type perovskite oxide of the first crystal phase is represented by a compositional formula: (K a Na b Li c C d ) e (D f E g )O h (where the element C comprises one or more elements selected from the group consisting of Ca, Sr, and Ba, the element D comprises one or more elements selected from the group consisting of Nb, Ta, Ti, Zr, Hf, Sn, Sb, and Si while comprising at least Nb or Ta, and the element E comprises one or more elements selected from the group consisting of Mg, Al, Sc, Mn, Fe, Co, Ni, Zn, Ga, and Y, and where a+b+c+d=1, e is arbitrary, f+g=1, and h is an arbitrary value that forms perovskite).

12. The lead-free piezoelectric ceramic composition according to claim 11 ,
wherein the coefficient e satisfies 0.88≤e≤1.07.

13. The lead-free piezoelectric ceramic composition according to claim 1 ,
wherein the alkali niobate/tantalate type perovskite oxide comprises an alkali niobate type perovskite oxide.

14. A piezoelectric element, comprising:
a piezoelectric ceramic comprising the lead-free piezoelectric ceramic composition according to claim 1 ; and
an electrode mounted on the piezoelectric ceramic.

15. A device comprising the piezoelectric element according to claim 14 .

16. The device according to claim 15 ,
wherein the device comprises any one of a knock sensor, an ultrasonic transducer, a cutting tool, an ultrasonic sensor, and an actuator.

17. A process for production of the lead-free piezoelectric ceramic composition according to claim 1 , the process comprising:
preparing a first powder by mixing and calcining raw materials of the first crystal phase;
preparing a second powder by mixing and calcining raw materials of the second crystal phase; and
producing the lead-free piezoelectric ceramic composition by mixing the first and second powders, molding the mixed powder material into a green body, and then firing the green body,
wherein the firing comprises sealed firing that is performed by sealing the green body in a closed container.

Assignees

• Ngk Spark Plug Co

Inventors

• Yamazaki Masato
• Matsuoka Takayuki
• Kitamura Kazuaki
• Kozuka Hisashi
• Yamada Hideto
• Kurahashi Toshiaki
• Okimura Yasuyuki
• Ohbayashi Kazushige
• Kasashima Takashi

Classifications

• G01L23/222

  using piezoelectric devices · CPC title

• C04B2235/3232

  Titanium oxides or titanates, e.g. rutile or anatase · CPC title

• H01L41/1132

  Electricity · mapped topic

• H01L41/187

  Electricity · mapped topic

• C04B2235/3234

  Titanates, not containing zirconia · CPC title