Carbon dioxide gas sensors and method of manufacturing and using same

Inventors

Hunter, Gary W. • Xu, Jennifer C.

Assignees

National Aeronautics and Space Administration NASA

Abstract

A gas sensor comprises a substrate layer; a pair of interdigitated metal electrodes, said electrodes include upper surfaces, the electrodes selected from the group consisting of Pt, Pd, Au, Ir, Ag, Ru, Rh, In, Os, and their alloys. A first layer of solid electrolyte staying in between electrode fingers and partially on said upper surfaces of said electrodes, said first layer selected from NASICON, LISICON, KSICON and β″-Alumina. A second layer of metal carbonate(s) as an auxiliary electrolyte engaging said upper surfaces of the electrodes and the first solid electrolyte. The metal carbonates selected from the group consisting of the following ions Na+, K+, Li+, Ag+, H+, Pb2+, Sr2+, Ba2+, and any combination thereof. An extra layer of metal oxide selected from the group consisting of SnO2, In2O3, TiO2, WO3, ZnO, Fe2O3, ITO, CdO, U3O8, Ta2O5, BaO, MoO2, MoO3, V2O5, Nb2O5, CuO, Cr2O3, La2O3, RuO3, RuO2, ReO2, ReO3, Ag2O, CoO, Cu2O, SnO, NiO, Pr2O3, BaO, PdO2, HfO3, HfO3 or other metal oxide and their mixtures residing above and in engagement with the second electrolyte to improve sensor performance and/or to reduce sensor heating power consumption.

Core Innovation

The invention relates to a miniaturized amperometric electrochemical carbon dioxide (CO2) sensor using a novel and robust sensor design. It comprises a substrate layer with interdigitated metal electrodes made of materials such as platinum, palladium, and others. A first solid electrolyte layer selected from NASICON, LISICON, KSICON, and β″-Alumina resides in between the electrode fingers and partially on their upper surfaces, and a second layer of metal carbonates as an auxiliary electrolyte engages the upper surfaces of the electrodes and the first solid electrolyte. An additional layer of metal oxide is applied above and in engagement with the second electrolyte to improve sensor performance and reduce power consumption. Semiconductor microfabrication techniques are used for fabrication, resulting in a small sensor size with a sensing area of approximately 1.0 mm by 1.1 mm and capable of operation from 200° C. to 600° C.

The problem being solved addresses shortcomings of conventional bulk or thick-film solid electrolyte CO2 sensors, which are large, consume high power, are costly, and difficult to batch fabricate. Prior miniaturized sensors also suffer from instability and poor integration due to deposition of electrolytes beneath the electrodes leading to erosion or looseness, and the difficulty of achieving perfect alignment in photolithographic manufacturing processes. The invention overcomes these issues by depositing interdigitated electrodes directly on the substrate with strong adhesion, applying the solid electrolyte primarily between electrode fingers, and covering the entire sensing area with auxiliary electrolyte and an extra metal oxide layer, achieving robust structure, improved sensitivity, selectivity, response time, and stability, along with simple batch fabrication and lower operational power consumption.

Claims Coverage

The patent includes multiple independent claims covering both processes for sensing carbon dioxide and the structure of the gas sensor device itself, each focusing on the multilayer sensor design and fabrication methods with specific materials and arrangements.

The claims define a robust and miniaturized electrochemical CO2 sensor design using a layered structure of interdigitated metal electrodes, solid electrolytes, auxiliary carbonate electrolytes, and an added metal oxide layer for enhanced sensor performance at reduced operating temperatures. The invention also covers corresponding fabrication processes employing photolithographic patterning and controlled material deposition.

Stated Advantages

Documented Applications