Fergusonite-type CeNbO4+: Single crystal growth, symmetry revision and conductivity

Abstract

Large fergusonite-type ( AB O 4 , A =Ce, B =Nb) oxide crystals, a prototype electrolyte composition for solid oxide fuel cells (SOFC), were prepared for the first time in a floating zone mirror furnace under air or argon atmospheres. While CeNbO 4 grown in air contained CeNbO 4.08 as a minor impurity that compromised structural analysis, the argon atmosphere yielded a single phase crystal of monoclinic CeNbO 4 , as confirmed by selected area electron diffraction, powder and single crystal X-ray diffraction. The structure was determined in the standard space group setting C 12/ c 1 (No. 15), rather than the commonly adopted I 12/ a 1. AC impedance spectroscopy conducted under argon found that stoichiometric CeNbO 4 single crystals showed lower conductivity compared to CeNbO 4+ δ confirming interstitial oxygen can penetrate through fergusonite and is responsible for the higher conductivity associated with these oxides. Large fergusonite-type CeNbO 4 crystals were prepared for the first time in a floating zone mirror furnace. Crystal growth in an argon atmosphere yielded a single phase monoclinic CeNbO4, as confirmed by selected area electron diffraction, powder and single crystal X-ray diffraction. The structure was determined in the standard space group setting C12/c1 (No. 15), rather than the commonly adopted I12/a1. AC impedance spectroscopy found CeNbO 4 single crystals showed lower conductivity compared to CeNbO 4+δ confirming interstitial oxygen can penetrate through fergusonite and is responsible for the higher conductivity associated with these oxides. • Preparation of single crystals of CeNbO 4 using a floating zone mirror furnace. • Correction to the crystal symmetry of the monoclinic form of CeNbO 4 . • Report the conductivity of a single crystal of CeNbO 4 .