Abstract: An oxygen probe assembly comprising an oxygen sensor (5) and means (8, 3) for directing a test gas and reference gas to the appropriate electrodes (7, 1) of the sensor, said assembly having associated therewith catalyst means (13, 6) arranged so that the test gas, the reference gas, or both said gases are separately contacted with the catalyst means before approaching the working surface(s) of the electrodes, whereby combustibles in the gases are oxidized; and/or means whereby the test gas, the reference gas, or both of said gases are conveyed to the said working surface(s) by way of a path (10, 4) which is of sufficient length to allow the said gas or gases to attain thermodynamic equilibrium at the probe temperature before coming into contact with the said working surface(s).

Abstract: An electrode for a solid electrolyte oxygen sensor, characterized in that the electrode comprises a surface layer on the solid electrolyte, said surface layer consisting of or containing a solid solution in urania of one or more other metal oxides with oxygen/metal atom ratio equal to or less than two, provided that at least one of said other metal oxides has an oxygen/metal atom ratio less than two.

Abstract: An oxygen sensor is composed of or contains a composite solid electrolyte material and, optionally, a body of a non-conducting ceramic material. The composite solid electrolyte material comprises a mixture of at least two constituents, one of which is a good oxygen ion conductor and the other a non-electrolyte ceramic. Magnesium aluminate spinel may be used for the non-conducting ceramic material in the composite solid electrolyte and for the body of the oxygen sensor.

Abstract: A composite solid electrolyte material for use in oxygen sensors, which comprises a mixture of at least two ceramic constituents, one of which is a good oxygen ion conductor and the other a non-electrolyte, is useful for oxygen sensor fabrication. Particularly, it enables gas analysis oxygen sensors to be produced by conventional techniques because the coefficient of thermal expansion of the composite electrolyte material can be closely matched to the material of a supporting sensor body. The closeness of thermal expansion coefficients means that oxygen sensors can now be formed in the "green" state, then fired.