Piezoelectric thin film, piezoelectric actuator, inkjet head, inkjet printer, and method for manufacturing piezoelectric actuator

Patent metadata

Field	Value
Publication number	US-10369787-B2
Application number	US-201615575644-A
Country	US
Kind code	B2
Filing date	May 11, 2016
Priority date	May 25, 2015
Publication date	Aug 6, 2019
Grant date	Aug 6, 2019

Abstract

A piezoelectric thin film is formed by adding a donor element to lead zirconate titanate. In the piezoelectric thin film, a molar ratio of lead to a total sum of zirconium and titanium is 105% or higher, and, when positive and negative coercive electric fields in polarization and electric field hysteresis are referred to as Ec (+) and Ec (−), respectively, a value of |Ec (+) |/|Ec (−) | is 0.5 or more and 1.5 or less.

First claim

The invention claimed is:

1. A piezoelectric thin film obtained by adding a donor element to lead zirconate titanate, wherein a molar ratio of lead to a total sum of zirconium and titanium is 105% or higher, and
wherein, when positive and negative coercive electric fields in polarization and electric field hysteresis are referred to as Ec (+) and Ec (−), respectively, a value of |Ec (+) |/|Ec (−) | is 0.5 or more and 1.5 or less;
wherein the donor element is lanthanum,
wherein a molar ratio of the lanthanum to the total sum of the zirconium and the titanium is 6% or more and 10% or less, and
wherein a molar ratio of the zirconium to the total sum of the zirconium and the titanium is 54% or more and 59% or less.

2. The piezoelectric thin film according to claim 1 , wherein internal stress of the film is 50 MPa or more and 250 MPa or less.

3. The piezoelectric thin film according to claim 1 , wherein breaking stress of the film is 400 MPa or more.

4. The piezoelectric thin film according to claim 1 , wherein the donor element is niobium,
wherein a molar ratio of the niobium to the total sum of the zirconium and the titanium is 10% or more and 20% or less, and
wherein a molar ratio of the zirconium to the total sum of the zirconium and the titanium is 52% or more and 59% or less.

5. A piezoelectric actuator comprising:
the piezoelectric thin film according to claim 1 ; and
a substrate adapted to support the piezoelectric thin film.

6. The piezoelectric actuator according to claim 5 , wherein, between the substrate and the piezoelectric thin film, a seed layer adapted to control crystalline orientation of the piezoelectric thin film is formed.

7. The piezoelectric actuator according to claim 6 , wherein the seed layer is made of lead lanthanum titanate.

8. The piezoelectric actuator according to claim 5 , further comprising:
a pair of electrodes adapted to apply voltage to the piezoelectric thin film.

9. A method for manufacturing the piezoelectric actuator according to claim 6 , comprising:
forming the piezoelectric thin film on the seed layer at a film forming rate of 2.5 μm/h or less.

10. An inkjet head comprising:
the piezoelectric actuator according to claim 5 ; and
a nozzle substrate including a nozzle hole through which ink contained in an opening portion formed in the substrate of the piezoelectric actuator is ejected outward.

11. An inkjet printer comprising:
the inkjet head according to claim 10 ,
wherein ink is ejected from the inkjet head toward a recording medium.

12. The piezoelectric thin film according to claim 1 ,
wherein the donor element is lanthanum.

13. A method for manufacturing the piezoelectric actuator according to claim 5 , comprising:
forming the piezoelectric thin film at a film forming rate of 2.5 μm/h or less.

14. The piezoelectric thin film according to claim 2 , wherein breaking stress of the film is 400 MPa or more.

15. The piezoelectric thin film according to claim 2 , wherein the donor element is lanthanum,
wherein a molar ratio of the lanthanum to the total sum of the zirconium and the titanium is 6% or more and 10% or less, and
wherein a molar ratio of the zirconium to the total sum of the zirconium and the titanium is 54% or more and 59% or less.

16. The piezoelectric thin film according to claim 2 , wherein the donor element is niobium,
wherein a molar ratio of the niobium to the total sum of the zirconium and the titanium is 10% or more and 20% or less, and
wherein a molar ratio of the zirconium to the total sum of the zirconium and the titanium is 52% or more and 59% or less.

17. A piezoelectric actuator comprising:
the piezoelectric thin film according to claim 2 ; and
a substrate adapted to support the piezoelectric thin film.

18. The piezoelectric thin film according to claim 3 , wherein the donor element is lanthanum,
wherein a molar ratio of the lanthanum to the total sum of the zirconium and the titanium is 6% or more and 10% or less, and
wherein a molar ratio of the zirconium to the total sum of the zirconium and the titanium is 54% or more and 59% or less.

19. The piezoelectric thin film according to claim 3 , wherein the donor element is niobium,
wherein a molar ratio of the niobium to the total sum of the zirconium and the titanium is 10% or more and 20% or less, and
wherein a molar ratio of the zirconium to the total sum of the zirconium and the titanium is 52% or more and 59% or less.

Assignees

• Konica Minolta Inc

Inventors

• Mawatari Kenji

Classifications

• C04B2235/3227

  Lanthanum oxide or oxide-forming salts thereof · CPC title

• C23C14/08

  Oxides (C23C14/10 takes precedence) · CPC title

• B41J2/1642

  thin film formation by CVD [chemical vapor deposition] · CPC title

• C04B2235/3251

  Niobium oxides, niobates, tantalum oxides, tantalates, or oxide-forming salts thereof · CPC title

• B41J2/16

  Production of nozzles · CPC title