Low yttria-doped cubic zirconium oxide nitride single crystals with high nitrogen contents show unexpected high oxygen ion conductivity in a temperature range between 100 degrees C and 300 degrees C. The observed values are about two orders of magnitude higher than the conductivities for conventionally used 9.5 YSZ. This can be related to an optimal anion vacancy concentration within the oxide nitride material and the low activation energy of the vacancy-based conductivity process. (C) 2016 Elsevier B.V. All rights reserved.