The development of novel trivalent ion conducting solids and their application for gas sensors

An exceptionally high Al3+ ion conducting polycrystalline solid based on the NASICON type structure was successfully realized within the system (AlxZr1−x)4/(4−x)Nb(PO4)3. The partial substitution of the smaller higher valent Nb5+ ion for Zr4+ helped stabilize and accommodate the mobile Al3+ ion into the NASICON like structure. The addition of boron oxide to the Al3+ ion conducting solid electrolyte, as a sintering additive, aided in the achievement of satisfactory mechanical strength and density for practical use. Environmental gas sensors were fabricated by combining the (AlxZr1−x)4/(4−x)Nb(PO4)3 solid electrolyte with yttria stabilized zirconia (YSZ) and appropriate auxiliary electrodes. The Nernst-like electrochemical sensors demonstrated rapid and reproducible response to CO2 and NOx, thereby promising excellent potential for environmental monitoring applications.