PTC thermistor ceramic composition and PTC thermistor element

Patent metadata

Field	Value
Publication number	US-9697935-B2
Application number	US-201414774824-A
Country	US
Kind code	B2
Filing date	Feb 17, 2014
Priority date	Mar 11, 2013
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A barium titanate based PTC thermistor ceramic composition without using Pb. Its Curie temperature is shifted to a temperature higher than 120° C. The PTC thermistor can readily turn semiconductive even if it is sintered in air. The resistivity at 25° C. is low and the variation rate of the resistivity at 25° C. with time is little. The PTC thermistor ceramic composition includes a sintered body having a barium titanate based compound represented by formula (1) as the main component, (Ba 1-x-y-w Bi x A y RE w ) α (Ti 1-z TM z )O 3 (1), wherein, 1.02y≦x≦1.5y (2), 0.007≦y≦0.125 (3), 0≦(w+z)≦0.01 (4), 0.97≦α≦1.06 (5), and the sintered body contains Ca in a ratio of 0.01 mol or more and less than 0.05 mol relative to 1 mol of Ti site in terms of element.

First claim

What is claimed is:

1. A PTC thermistor ceramic composition, comprising
a sintered body comprising a barium titanate based compound represented by the following formula (1) as the main component,
(Ba 1-x-y-w Bi x A y RE w ) α (Ti 1-z TM z )O 3   (1),

wherein, in the formula (1), A represents at least one element selected from the group consisting of Na and K,
RE represents at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy and Er,
TM represents at least one element selected from the group consisting of V, Nb and Ta, and
w, x, y, z and α satisfy the following in equations (2) to (5), in which, the units of w, x, y and z are all mole, and a represents the molar ratio of Ba site to Ti site,
1.02 y≦x≦ 1.5 y   (2)

0.007≦ y≦ 0.125  (3)

0≦( w+z )≦0.01  (4)

0.97≦α≦1.06  (5), and

Ca is further contained in a ratio of 0.01 mol or more and less than 0.05 mol relative to 1 mol of Ti site in terms of element.

2. The PTC thermistor ceramic composition of claim 1 , wherein,
Si is further contained in the PTC thermistor ceramic composition in a ratio of 0.035 mol or less relative to 1 mol of Ti site in terms of element.

3. The PTC thermistor ceramic composition of claim 2 , wherein,
Mn is further contained in the PTC thermistor ceramic composition in a ratio of 0.0015 mol or less relative to 1 mol of Ti site in terms of element.

4. The PTC thermistor ceramic composition of claim 3 , wherein,
both Na and K are contained as A in the PTC thermistor ceramic composition, and the molar ratio of Na to K is in the range of 6/4 or more and 9/1 or less.

5. A PTC thermistor comprising a ceramic element and electrodes formed on the surface of the ceramic element, wherein,
the ceramic element is formed by using the PTC thermistor ceramic composition of claim 4 .

6. A PTC thermistor comprising a ceramic element and electrodes formed on the surface of the ceramic element, wherein,
the ceramic element is formed by using the PTC thermistor ceramic composition of claim 3 .

7. The PTC thermistor ceramic composition of claim 2 , wherein,
both Na and K are contained as A in the PTC thermistor ceramic composition, and the molar ratio of Na to K is in the range of 6/4 or more and 9/1 or less.

8. A PTC thermistor comprising a ceramic element and electrodes formed on the surface of the ceramic element, wherein,
the ceramic element is formed by using the PTC thermistor ceramic composition of claim 7 .

9. A PTC thermistor comprising a ceramic element and electrodes formed on the surface of the ceramic element, wherein,
the ceramic element is formed by using the PTC thermistor ceramic composition of claim 2 .

10. The PTC thermistor ceramic composition of claim 1 , wherein,
Mn is further contained in the PTC thermistor ceramic composition in a ratio of 0.0015 mol or less relative to 1 mol of Ti site in terms of element.

11. The PTC thermistor ceramic composition of claim 10 , wherein,
both Na and K are contained as A in the PTC thermistor ceramic composition, and the molar ratio of Na to K is in the range of 6/4 or more and 9/1 or less.

12. A PTC thermistor comprising a ceramic element and electrodes formed on the surface of the ceramic element, wherein,
the ceramic element is formed by using the PTC thermistor ceramic composition of claim 11 .

13. A PTC thermistor comprising a ceramic element and electrodes formed on the surface of the ceramic element, wherein,
the ceramic element is formed by using the PTC thermistor ceramic composition of claim 10 .

14. The PTC thermistor ceramic composition of claim 1 , wherein,
both Na and K are contained as A in the PTC thermistor ceramic composition, and the molar ratio of Na to K is in the range of 6/4 or more and 9/1 or less.

15. A PTC thermistor comprising a ceramic element and electrodes formed on the surface of the ceramic element, wherein,
the ceramic element is formed by using the PTC thermistor ceramic composition of claim 14 .

16. A PTC thermistor comprising a ceramic element and electrodes formed on the surface of the ceramic element, wherein,
the ceramic element is formed by using the PTC thermistor ceramic composition of claim 1 .

Assignees

• Tdk Corp

Inventors

• Itoh Kazuhiko
• Shimura Yoshikazu

Classifications

• C04B2235/3201

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

• C04B2235/3239

  Vanadium oxides, vanadates or oxide forming salts thereof, e.g. magnesium vanadate · CPC title

• C04B2235/3262

  Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO · CPC title

• H01C7/025 Primary

  Perovskites, e.g. titanates · CPC title

• C04B2235/3227

  Lanthanum oxide or oxide-forming salts thereof · CPC title