Lead-free piezo-electric porcelain composition, piezo-electric element using the same, and method for producing lead-free piezo-electric porcelain composition

Patent metadata

Field	Value
Publication number	US-9871187-B2
Application number	US-201514682631-A
Country	US
Kind code	B2
Filing date	Apr 9, 2015
Priority date	Apr 11, 2014
Publication date	Jan 16, 2018
Grant date	Jan 16, 2018

Abstract

A lead-free piezo-electric porcelain composition which contains a main phase having voids and which is formed of a first crystal phase composed of an alkali niobate/tantalate-based perovskite oxide having piezo-electric characteristics; and a sub-phase containing a second crystal phase composed of an A 2 B 6 O 13 -based compound (where the element A is a monovalent element and the element B is one or more divalent to hexavalent elements). The sub-phase fills voids present in the main phase.

First claim

What is claimed is:

1. A lead-free piezo-electric porcelain composition comprising:
a main phase having voids and which is formed of a first crystal phase composed of an alkali niobate/tantalate-based perovskite oxide having piezo-electric characteristics; and
a sub-phase containing a second crystal phase composed of an A 2 B 6 O 13 -based compound, where the element A is a monovalent element and the element B is one or more divalent to hexavalent elements,
wherein the sub-phase fills the voids present in the main phase.

2. The lead-free piezo-electric porcelain composition as claimed in claim 1 , wherein the element A includes at least one metal element selected from the group consisting of Li, Na and K and the element B includes at least one metal element selected from the group consisting of Co, Fe, Mg, Ni, Zr, Zn, Mn, Al, Nb, Ta, W and Ti.

3. The lead-free piezo-electric porcelain composition as claimed in claim 1 , wherein the element B includes at least Mg.

4. The lead-free piezo-electric porcelain composition as claimed in claim 1 , wherein the A 2 B 6 O 13 -based compound has a layered structure.

5. The lead-free piezo-electric porcelain composition as claimed in claim 1 , wherein the content ratio of the second crystal phase in the lead-free piezo-electric porcelain composition is any of the following:
(i) 0.30% by volume or more and 3.10% by volume or less,
(ii) 0.50% by volume or more and 2.50% by volume or less, and
(iii) 1.00% by volume or more and 2.00% by volume or less.

6. The lead-free piezo-electric porcelain composition as claimed in claim 1 , wherein the volume ratio of the second crystal phase is larger than 50% when the whole of the sub-phase is taken as 100%.

7. The lead-free piezo-electric porcelain composition as claimed in claim 1 , Wherein the alkali niobate/tantalate-based perovskite oxide forming the first crystal phase contains an alkaline earth metal.

8. The lead-free piezo-electric porcelain composition as claimed in claim 1 , wherein the alkali niobate/tantalate-based perovskite oxide forming 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 is one or more selected from the group consisting of Ca, Sr, Ba, and Rb, the element D is one or more, including at least Nb or Ta, selected from the group consisting of Nb, Ta, Ti and Zr, the element E is one or more selected from the group consisting of Mg, Al, Sc, Mn, Fe, Co, Ni, Zn, Ga and Y, a+b+c+d=1, e is any value, f+g=1, and h is any value that forms a perovskite.

9. The lead-free piezo-electric porcelain composition as claimed in claim 8 , wherein the coefficient e satisfies 0.80≦e≦1.30.

10. A piezo-electric element comprising:
a piezo-electric porcelain formed of the lead-free piezo-electric porcelain composition as claimed in claim 1 , and
an electrode attached to the piezo-electric porcelain.

11. A method for producing the lead-free piezo-electric porcelain composition as claimed in claim 1 , the method comprising:
mixing and calcining constituent raw materials of the first crystal phase to form a first powder,
mixing and calcining constituent raw materials of the second crystal phase to form a second powder, and
forming the lead-free piezo-electric porcelain composition by mixing the first powder and the second powder, molding to form a green body and firing,
wherein the firing is closed firing performed while the green body is enclosed in a closed vessel.

Assignees

• Ngk Spark Plug Co

Inventors

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

Classifications

• C04B2235/3201

  Alkali metal oxides or oxide-forming salts thereof · CPC title

• C04B2235/3251

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

• C04B35/495 Primary

  based on vanadium, niobium, tantalum, molybdenum or tungsten oxides or solid solutions thereof with other oxides, e.g. vanadates, niobates, tantalates, molybdates or tungstates · CPC title

• C04B2235/3213

  Strontium oxides or oxide-forming salts thereof · CPC title

• C04B2235/3208

  Calcium oxide or oxide-forming salts thereof, e.g. lime · CPC title