Compositions, apparatus and methods for capacitive temperature sensing

Patent metadata

Field	Value
Publication number	US-2016223408-A1
Application number	US-201414917570-A
Country	US
Kind code	A1
Filing date	Sep 11, 2014
Priority date	Sep 25, 2013
Publication date	Aug 4, 2016
Grant date	—

Abstract

A passive temperature-sensing apparatus, which includes a capacitive sensing element that includes a capacitive sensing composition that includes a ferroelectric ceramic material that exhibits a measurable electrical Curie temperature that is below 30 degrees C. The capacitive sensing composition exhibits a negative slope of capacitance versus temperature over the temperature range of from 30 degrees C. to 150 degrees C.

First claim

What is claimed is:

1 . A passive temperature-sensing apparatus, the apparatus comprising a capacitive sensing element that comprises a capacitive sensing composition that includes a ferroelectric ceramic material that exhibits a measurable electrical Curie temperature that is below 30 degrees C., and wherein the capacitive sensing composition exhibits a negative slope of capacitance versus temperature over the temperature range of from 30 degrees C. to 150 degrees C.

2 . The apparatus of claim 1 wherein the capacitive sensing element comprises a multilayer ceramic capacitor comprising alternating layers of the capacitive sensing composition and a conductive material.

3 . The apparatus of claim 1 wherein the capacitive sensing composition comprises particles of the ferroelectric ceramic material that are dispersed in a polymer matrix.

4 . The apparatus of claim 3 wherein the polymeric matrix is selected from the group consisting of thermoplastic materials and thermoset materials.

5 . The apparatus of claim 3 wherein the polymer matrix comprises polymers selected from the group consisting of: silicones; epoxies; ethylene-propylene-dienes; polyolefins; polyurethanes; epichlorohydrins; fluoroelastomers; and copolymers, blends and/or mixtures thereof.

6 . The apparatus of claim 3 wherein the ferroelectric ceramic material comprises between about 15 weight % and about 90 weight % of the capacitive sensing composition.

7 . The apparatus of claim 1 wherein the ferroelectric ceramic material is chosen from the group consisting of doped BaTiO 3 , BaSnTiO 3 , BaHMO 3 , BaSrTiO 3 , BaZrTiO 3 , SrTiO 3 , BaFe 12 O 19 , Pb[Zr x Ti (1-x) ]O 3 , and x[Pb(Mg 1/3 Nb 2/3 )O 3 ]-(1−x)[PbTiO 3 ], and combinations and mixtures thereof.

8 . The apparatus of claim 1 wherein the ferroelectric ceramic material is chosen from the group consisting of BaM x Ti 1-x O 3 , where M=Zr or Sn and where 0.1≦x≦0.8.

9 . The apparatus of claim 1 wherein the ferroelectric ceramic material is chosen from the group consisting of BaZr x Ti 1-x O 3 , where 0.1≦x≦0.3.

10 . The apparatus of claim 1 wherein the ferroelectric ceramic material is chosen from the group consisting of BaSn x Ti 1-x O 3 , where 0.1≦x≦0.3.

11 . The apparatus of claim 1 wherein the negative slope of capacitance versus temperature over the temperature range of from 30 degrees C. to 150 degrees C., is greater in magnitude than about −2% per 10 degrees C.

12 . The apparatus of claim 1 wherein the negative slope of capacitance versus temperature over the temperature range of from 30 degrees C. to 150 degrees C., is greater in magnitude than about −4% per 10 degrees C.

13 . The apparatus of claim 1 wherein the negative slope of capacitance versus temperature over the temperature range of from 30 degrees C. to 150 degrees C., is greater in magnitude than about −16% per 10 degrees C.

14 . The apparatus of claim 1 wherein the capacitive sensing composition exhibits a loss tangent of about 0.05 or less over the temperature range of from 30 degrees C. to 150 degrees C. at a frequency of 1 kHz-20 MHz.

15 . The apparatus of claim 1 wherein the capacitive sensing element is a capacitive element of an L-C circuit.

16 . The apparatus of claim 15 wherein the capacitive sensing element is in thermal communication with a portion of a high voltage power cable.

17 . The apparatus of claim 16 further comprising a unit configured to detect a resonant frequency of the L-C circuit.

18 . A method of monitoring a temperature of a portion of a high voltage power cable, the method comprising:
detecting a resonant frequency of an L-C circuit that comprises a capacitive sensing element that is in thermal communication with a potion of the high voltage power cable,
wherein the capacitive sensing element comprises a capacitive sensing composition that includes a ferroelectric ceramic material that exhibits a measurable electrical Curie temperature that is below 30 degrees C.,
and wherein the capacitive sensing composition exhibits a negative slope of capacitance versus temperature over the temperature range of from 30 degrees C. to 150 degrees C.

Assignees

• 3M Innovative Properties Co

Inventors

• Ghosh Dipankar
• Kang Myungchan
• Kim Jaewon

Classifications

• H01G7/04

  having a dielectric selected for the variation of its permittivity with applied temperature · CPC title

• C01G23/006

  Alkaline earth titanates · CPC title

• C04B2235/3244

  Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof · CPC title

• H01G7/06

  having a dielectric selected for the variation of its permittivity with applied voltage, i.e. ferroelectric capacitors (electrets H01G7/02) · CPC title

• C01G25/006

  Compounds containing zirconium, with or without oxygen or hydrogen, and containing two or more other elements · CPC title