Compositions – Electrically conductive or emissive compositions – Metal compound containing
Reexamination Certificate
2000-09-12
2001-08-07
Kopec, Mark (Department: 1751)
Compositions
Electrically conductive or emissive compositions
Metal compound containing
C252S521200, C338S0220SD, C338S225000
Reexamination Certificate
active
06270693
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermistor composition having a preferred resistance value and B constant and being available in a wide temperature range from room temperature to higher temperatures such as 400° C.
2. Description of the Related Art
Sintered products, such as metal oxides of the Mn—Ni or Mn—Ni—Co composition, have been known as thermistors in the art.
These thermistor compositions are desired to have a wide range of resistivity. Various types of thermistor composition have been provided in response to this requirement. The sintered substance has a B constant of approximately 2,000-5,000 K and its resistance value varies by 2-5% when the temperature varies by 1° C. near room temperature. Therefore, it is possible to measure the temperature at a high precision, approximately {fraction (1/100+L )}° C. on the basis of the resistance value of such a thermistor. Accordingly, it can be widely used as a temperature sensor near room temperature due to this property.
The thermistor used near room temperature, however, is disadvantageous because its resistivity varies remarkably when it is used at temperatures above 250° C. for a long period of time.
In order to solve this problem, JP 62-11201A discloses a thermistor device having a metal oxide of the Mn—Ni composition into which SiO
2
is added, wherein the variation of resistance characteristic in a high temperature range of 300-500° C. is reduced. This thermistor device, however, is not suitably available near room temperature because its resistivity increases remarkably.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a thermistor composition which is useful within a wide temperature range from room temperature to 400° C.
Another object of the present invention is to provide a thermistor using the above-mentioned thermistor composition.
A further object of the present invention is to provide a thermistor device using the above-mentioned thermistor.
The present invention is directed to a thermistor composition having a general formula Mn
2−a−b−c
Zn
a
Ni
b
Fe
c−d
Co
1−d
O
4
, wherein 0.1≦a<1, 0≦b<1, 0<c<1, 0≦d<1 and 0.1<a+b<1.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof.
REFERENCES:
patent: 5731049 (1998-03-01), Tailhades et al.
Abd et al; “Study of The Jump Length Effect on The Physical Properties of Mn-Doped Co0.6Zn0.4Ferrites”Phys. Stat. Sol.(9) 157,523 pp 523-529, 1996.*
Henaish “Thermal Studies on Doped Cobalt -Zluc Ferrite”Indian Ceram.(1995), 38(2) Abstract Only.*
Elshora et al. “Dielectric Properties of Co6Zn4MmxFez−xO4”Proc Indian Natl Sci. Acad, Part A (1994) Abstract Only.*
Patent Abstract of Japan, Publication 07022206 A dated Jul. 6, 1993 and translation.
JP Application No. 60-150998 dated Jul. 8, 1985 and translation.
Hamada Kazuyuki
Oda Hiroshi
Kopec Mark
Pitney Hardin Kipp & Szuch LLP
Ube Industries Ltd.
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