Ionic and electronic conductivity of nitrogen-doped YSZ single crystals

Structure and conductivity of yttria and scandia‐doped zirconia crystals grown by skull melting

“…As it was shown in, 21 the specific grain boundary (ie, the interfaces between adjacent grains) conductivity of YSZ is about two orders of magnitude lower than its bulk conductivity. Single crystals of fully and partially stabilized YSZ, 28,29 nitrogen-doped YSZ, 30 (Ce x Zr 1-x ) 0.8 Y 0.2 O 1.9-d , 31 , and Ce 0.8 Y 0.2 O 2-d 32 have been grown by the skull melting technique. 22,23 In addition, the effect may be related to segregation of yttrium cations on the ZrO 2 grain boundaries which leads to creation of the space charge effect that reduces the conductivity.…”

Growth of yttria-doped zirconium oxide nitride single crystals by means of reactive skull melting

“…However, no significant increase of nitrogen concentration in the resulting crystal was observed. Analysis of the nitrogen content of the sintering crust shows a high nitrogen content (0.91(1) wt% N) as observed for nitridation reactions of ceramics [6,20], demonstrating that nitridation of solid zirconia in direct contact with the atmosphere is possible but nitrogen solubility in the melt is rather poor.…”

“…This result shows that even direct nitrogen supply into the melt did not increase the nitrogen content of the resulting crystals because nitrogen solubility seems to be determined by the nitrogen activity and the temperature of the melt. Former experiments have shown that a low oxygen activity is necessary to achieve high nitrogen contents in zirconia based materials [6]. However, the use of forming gas on one hand reduces significantly the oxygen activity in the gas atmosphere but on the other hand leads to a partial reduction of the resulting crystals.…”

“…In the last years several investigations on nitrogen ion mobility in nitrogen-doped zirconia-based materials have been carried out, revealing that nitrogen ion mobility can be principally realized and may be used for new applications requiring fast nitrogen ion conduction [6][7][8][9][10]. However, all investigations were carried out either on polycrystalline samples or on single crystals exhibiting the cubic fluorite-type phase even before nitrogen incorporation.…”

“…As a matter of fact, determination of electrical bulk properties from polycrystalline samples is less exact due to grain boundary effects causing a rather difficult correlation between the electrical properties and the crystal structure (defect structure). Furthermore, incorporation of nitrogen in the fully stabilized zirconia with a therefore higher anion vacancy concentration leads to a reduced overall electrical conductivity [6]. According to these facts, correlations of the electrical properties with the defect structure should be preferably investigated using single crystals.…”