Gte Laboratories Incorporated

Gte Control Devices Incorporated

Daniel T Kennedy

Da Y Wang

Burton W MacAllister, Jr

Thomas R Middleton

Kazumasa Umeya

Joanne Browne

A method of making a positive temperature coefficient of resistance (PTCR) device, and the PTCR device itself, where there is provided a ferroelectric semiconductor having a Curie point and a bulk resistance. A layer of electrically conducting material is provided upon the ferroelectric semiconductor. The layer is heated at a process temperature greater than the Curie point of the ferroelectric semiconductor for a period of time, and cooled to ambient temperature. The process temperature and time period are selected to be sufficent to provide an ambient layer resistance greater than the bulk resistance of the ferroelectric semiconductor. The layer may be heated in an oxidizing atmosphere or in a reducing atmosphere, which also affects the layer resistance. The ferroelectric semiconductor may be in the form of an oxide ceramic or liquid crystals, and may include barium titanate. The layer may be selected from the group consisting of metal, metal alloys, metal oxides, polymers, and composites thereof.

Method of making semiconducting ferroelectric PTCR devices

Apparatus and method for determining the concentration of NOx in a gas mixture. The gas mixture is supplied to two electrodes at which different NOx decomposition conditions are present. The electrodes may be of different materials or sizes or may be positioned in different gas enclosure environments. The NOx decomposes at different rates at the two electrodes and an emf is thus produced between the electrodes. The concentration of NOx in the gas mixture is determined from the measured emf.

Method and apparatus for sensing nox

A system of dielectric ceramic compositions suitable for various microwave applications. The system comprises a plurality of stoichiometrically-related compositions, each composition having its own particular set of dielectric properties and consisting essentially of a sintered mixture represented by the general formula:

System of dielectric ceramic compositions suitable for microwave

A method of making a positive temperature coefficient of resistance (PTCR) device,and the PTCR device itself, where there is provided a ferroelectric semiconductor having a Curie point and a bulk resistance. A layer of electrically conducting material is provided upon the ferroelectric semiconductor. The layer is heated at a process temperature greater than the Curie point of the ferroelectric semiconductor for a period of time. End cooled to ambient temperature. The process temperature and time period are selected to be sufficient to provide an ambient layer resistance greater than the bulk resistance of the ferroelectric semiconductor. The layer may be heated in an oxidizing atmosphere or in a reducing atmosphere which also affects the layer resistance. The ferroelectric semiconductor may be in the form of an oxide ceramic or liquid crystals, and may include barium titanate. The layer may be selected from the group consisting of metal, metal alloys, metal oxides, polymers, and composites thereof.

PTCR device

Apparatus and method for determining the identity and concentration of a component in a test atmosphere having a known concentration of oxygen. At least one solid electrolyte oxygen sensor is used, with each sensor having a solid electrolyte wall in contact with, and interposed between, a first electrode and a second electrode. The first electrode is in communication with the test atmosphere. A first negative voltage is applied across the first and second electrodes of a sensor, causing electrochemical oxygen pumping and a first electric current to flow through the corresponding solid electrolyte wall. The first negative voltage is selected to cause the first electric current magnitude to be on a first current plateau. The magnitude of the first electric current is measured. A second negative voltage is applied across the first and second electrodes of a sensor, causing electrochemical oxygen pumping and a second electrical current to flow through the corresponding solid electrolyte wall. The second negative voltage is selected to cause the second electric current magnitude to be on a second current plateau. The magnitude of said second electric current is measured. A table correlating pairs of numbers representing various combinations of first and second electric current with corresponding identity and concentration of one or more components is provided. The measured first and second magnitudes of electric current are matched with the pairs of numbers in the table and the corresponding identity and concentration of one or more component is determined.

Method for determining identification and concentration of an

Method and apparatus for sensing NOx

A fuel cell which converts chemical energy from a fuel/oxidant gas mixture to electricity for power usage or gas-sensing applications is disclosed. The fuel cell has a solid electrolyte wall with electrodes on each side. Each side of the wall is surrounded by a partition which forms a first and second chamber whereon the fuel/oxidant gas mixture is allowed to diffuse. Means are provided to initiate a voltage drop between the electrodes which initiates the chemical reaction. Electricity is collected from the electrodes. In an alternate design the fuel cell has a first and second electrolyte wall with electrodes on each side of the walls. A partition wall separates the first and second walls thereby forming a first chamber with the first wall and the partition wall and a second chamber with the partition wall and the second wall. Gas-flow limiting means exist between the fuel/oxidant gas mixture and the first chamber and the first chamber and the second chamber. The chemical reaction starts spontaneously and electricity is collected and stored from each set of electrodes.

Method and device for gaseous fuel cell operation

Apparatus and method for determining the identity and concentration of one or more components in a test atmosphere having a known concentration of oxygen. A solid electrolyte oxygen sensor is used, having a first solid electrolyte wall in contact with, and interposed between, a first electrode and a second electrode and a second solid electrolyte wall in contact with, and interposed between a third electrode and a fourth electrode. The second and fourth electrodes are in communication with the test atmosphere. A partition wall separates the first and third electrodes forming a first chamber bounded by the first wall and the partition wall and a second chamber bounded by the partition wall and the second wall. Diffusion limiting means inhibit gas-flow of the gas from the test atmosphere to the first chamber and from the first chamber to the second chamber. A first negative voltage (or positive voltage when the unknown component has a concentraion larger than that of a stoichiometric gas mixture) is applied to the first and second electrodes generating a first electrical current on a first electric current plateau. Simultaneously the EMF across the third and fourth electrodes is measured. These two numbers are correlated with a table to determine gas component identity and concentration. Alternatively a first negative voltage is applied to the first and second electrodes generating a first electrical current. Simultaneously a second negative voltage is applied to the third and fourth electrodes generating a second electrical current. The magnitudes of said first and second voltages are in contrast to each other (the first voltages is low and the second voltage is high or vise verse, with their difference kept at least 100 mV). The second current is measured and is correlated with a figure to determine gas concentration or hydrogen-equivalent gas concentration.

A method for identifying and determining the concentration of nitrous oxide in a gas containing nitrous oxide, oxygen and nitrogen is disclosed. A negative voltage is applied across a set of electrodes separated by an electrolyte wall. The voltage is of such a magnitude to produce an electric current which is on a plateau. The current is measured initially using air or oxygen as a test gas. After this reading is taken the gas containing nitrous oxide in oxygen and air is measured for its current and the concentration of nitrous oxide is determined using the two measured currents. The negative voltage can be applied at two different magnitudes to have two currents measured. Nitrous oxide containing mixtures would yield equivalent current readings.

Method for sensing nitrous oxide

Apparatus for measuring the concentration of oxygen in exhaust gases. A gas sensor element of yttria-stabilized zirconia (Y.sub.2 O.sub.3 -ZrO.sub.2) has at one end a gas pump of two chambers separated by intervening Y.sub.2 O.sub.3 -ZrO.sub.2 with an orifice extending between each chamber and the exterior of the gas sensor element. Two platinum electrodes of a first set face one chamber and two platinum electrodes of a second set face the other chamber. The gas sensor element is mounted in an insulating mounting collar in close contact with two ceramic heaters of resistance heating elements on silicon nitride substrates. The mounting collar is clamped between a shield member encircling the gas pump of the sensor element and a housing member by threaded clamping nuts. The shield member has one or more apertures therein to admit exhaust gases to be analyzed to the gas pump of the sensor element. The housing member has an electrical connector at one end which is spaced from the sensor element for providing electrical connections to the sensor element and the ceramic heaters.

Gas sensing apparatus

A layer of chemically compatible conductive material is applied to ferroelectric semiconductor material having a permanent polarization below its Curie temperature. The materials are heated to a temperature above the Curie temperature of the ferroelectric semiconductor material and allowed to cool. The result is a low resistance contact. The ferroelectric semiconductive material may be a layer on a non ferroelectric semiconductor material with a matching work function or matching dopant levels.

Method of making ohmic contact to ferroelectric semiconductors

Apparatus for measuring the concentration of oxygen in exhaust gases. A gas sensor element of yttria-stabilized zirconia (Y.sub.2 O.sub.3 -ZrO.sub.2) has at one end a gas pump of two chambers separated by intervening Y.sub.2 O.sub.3 -ZrO.sub.2 with an orifice extending between each chamber and the exterior of the gas sensor element. Two platinum electrodes of a first set face one chamber and two platinum electrodes of a second set face the other chamber. The gas sensor element is mounted in an insulating mounting collar in close contact with two ceramic heaters of resistance heating elements on silicon nitride substrates. The mounting collar is clamped between a shield member encircling the gas pump of the sensor element and a housing member by threaded clamping nuts. The shield member has one or more apertures therein to admit exhaust gases to be analyzed to the gas pump of the sensor element. The housing member has an electrical connector at one end which is spaced from the sensor element for providing electrical connections to the sensor element and ceramic heaters.

Gas sensor element

A gas concentration sensing or pumping device is formed of a body of solid electrolyte material which exhibits ionic conduction when the concentration of gas is different between first and second surfaces of the body, or which, upon application of a voltage across the body, will cause gas on one side of the body to be pumped to the other side. A thin film of a composition comprising an element selected from the group consisting of rare earth elements, alkaline earth metals, Ga Pb, In, Sn, Ti, Mo and W wherein Bi is the predominant element is formed on a major surface of the body to enhance conductivity at the electrode/body interface. Conductive electrode layers are formed over the film and an opposing major surface. The conductive layers may be formed of porous LaCrO.sub.3 and the body may be formed of ZrO.sub.2, CeO.sub.2 or ThO.sub.2. An apertured disc or a layer of gas permeable material is formed over the sensor. A voltage is applied across the body of solid electrolyte causing transport of oxygen through the aperture or pores. The output current measures the oxygen concentration passing therethrough.

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Burlington, MA, United States of America

Daniel T Kennedy