Carbon dioxide sensor
A carbon dioxide sensor includes: a solid electrolyte layer that is anion conductive; a reference electrode disposed on one surface of the solid electrolyte layer; and a detection electrode disposed on the other surface of the solid electrolyte layer. The detection electrode is made of a mixture containing: (a) one or more metals selected from the group consisting of Au, Ag, Pt, Pd, Rh, Ru, Os, and Ir; (b) a cation conductive carbonate; and (c) an oxide containing Li and at least one of Ce and Sm. The solid electrolyte layer is preferably oxide ion conductive, and the cation conductive carbonate is preferably lithium ion conductive.
1 . A carbon dioxide sensor comprising:
a solid electrolyte layer that is anion conductive;
a reference electrode disposed on one surface of the solid electrolyte layer; and
a detection electrode disposed on an opposite surface of the solid electrolyte layer,
wherein the detection electrode is made of a mixture containing:
particles of one or more metals selected from the group consisting of Au, Ag, Pt, Pd, Rh, Ru, Os, and Ir;
a cation conductive carbonate; and
particles of an oxide comprising Li 2 Ce x Sm y O 3 where x and y represent positive numbers, and x+y=1,
wherein the one or more metals are contained in an amount that ranges between 30 mass % or more and 60 mass % or less relative to a total mass of the one or more metals, the cation conductive carbonate, and the oxide, and
wherein a contact structure of the particles of the one or more metals and the particles of the oxide is continuously formed in the mixture.
2 . The carbon dioxide sensor according to claim 1 , wherein, in the mixture, the amount of the cation conductive carbonate is 5 mass % or more and 55 mass % or less relative to the total mass of the one or more metals, the cation conductive carbonate, and the oxide.
3 . The carbon dioxide sensor according to claim 1 , wherein, in the mixture, the amount of the oxide is 10 mass % or more and 60 mass % or less relative to the total mass of the one or more metals, the cation conductive carbonate, and the oxide.
4 . The carbon dioxide sensor according to claim 1 , further comprising a first intermediate layer between the solid electrolyte layer and the reference electrode, the first intermediate layer being made of cerium oxide doped with lanthanum and a rare-earth element, provided that lanthanum and cerium are excluded from the rare-earth element.
5 . The carbon dioxide sensor according to claim 1 , wherein the solid electrolyte layer is oxide ion conductive.
6 . The carbon dioxide sensor according to claim 1 , wherein the solid electrolyte layer is made of a compound containing M 1 , M 2 , and O,
where M 1 represents one or more elements selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Be, Mg, Ca, Sr, Y, and Ba, and
M 2 represents one or more elements selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Zr, Ta, Nb, B, Si, Ge, Zn, Sn, W, and Mo.
7 . The carbon dioxide sensor according to claim 6 , wherein M 1 includes at least La and Y.
8 . The carbon dioxide sensor according to claim 1 , wherein the solid electrolyte layer is made of a composite oxide represented by formula (1): M 9.33+x 1 [T 6.00−y M y 2 ]O 26.0+z , where M 1 represents one or more elements selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Be, Mg, Ca, Sr, Y, and Ba,
T represents either one or both of Si and Ge,
M 2 represents one or more elements selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Zr, Ta, Nb, B, Si, Ge, Zn, Sn, W, and Mo,
x represents a number of −1.33 or more and 1.50 or less,
y represents a number of 0.00 or more and 3.00 or less,
z represents a number of −5.00 or more and 5.20 or less, and
the ratio of the number of moles of M 1 to the number of moles of T is 1.33 or more and 3.61 or less.
9 . The carbon dioxide sensor according to claim 1 , wherein the solid electrolyte layer is made of a compound having an apatite crystal structure.
10 . The carbon dioxide sensor according to claim 1 , wherein the solid electrolyte layer has a thickness of 1 μm or more and 1000 μm or less.
11 . The carbon dioxide sensor according to claim 1 , wherein the detection electrode has a thickness of 5 μm or more and 2000 μm or less.
12 . The carbon dioxide sensor according to claim 1 , further comprising a second intermediate layer between the solid electrolyte layer and the detection electrode, the second intermediate layer being made of cerium oxide doped with lanthanum and a rare-earth element, provided that lanthanum and cerium are excluded from the rare-earth element.
13 . The carbon dioxide sensor according to claim 1 , wherein the cation conductive carbonate is contained in an amount that ranges between 7 mass % or more and 30 mass % or less relative to the total mass of the one or more metals, the cation conductive carbonate, and the oxide.
14 . The carbon dioxide sensor according to claim 1 , wherein the oxide is contained in an amount that ranges between 20 mass % or more and 40 mass % or less relative to total mass of the one or more metals, the cation conductive carbonate, and the oxide.
15 . The carbon dioxide sensor according to claim 1 , wherein the one or more metals have a particle size of 0.05 μm or more and 5 μm or less.
16 . A method for measuring a carbon dioxide concentration, the method comprising using the carbon dioxide sensor according to claim 1 at a temperature lower than or equal to 600° C.