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Effects of Annealing Temperature on the Structure and Capacitive Performance of Nanoscale Ti / IrO 2 – ZrO 2 Electrodes
Author(s) -
Shao YanQun,
Yi ZhaoYu,
He Chong,
Zhu JunQiu,
Tang Dian
Publication year - 2015
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.13475
Subject(s) - crystallinity , nanocrystalline material , amorphous solid , materials science , x ray photoelectron spectroscopy , crystallization , annealing (glass) , dielectric spectroscopy , oxide , analytical chemistry (journal) , chemical engineering , tin oxide , scanning electron microscope , cyclic voltammetry , electrode , electrochemistry , crystallography , nanotechnology , chemistry , composite material , metallurgy , chromatography , engineering
Electrodes consisting of coating of the Iridium oxide–Zirconium oxide (70%IrO 2 –30%ZrO 2 ) binary oxide were formed on Ti substrates by thermal decomposition and annealing at 340°C–450°C. The effects of the annealing temperature on the structure, surface morphology, surface composition, and capacitive performance of the coatings were investigated using X‐ray diffraction analysis (XRD), transmission electron microscopy (TEM), scanning electron microscopy, X‐ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The XRD and TEM analyses showed that 360°C is greater than but very close to the crystallization temperature of the 70%IrO 2 –30%ZrO 2 oxide coating. The 70%IrO 2 –30%ZrO 2 oxide coatings annealed at this temperature consisted of an amorphous matrix containing a few IrO 2 nanocrystalline particles (diameter of 1–2 nm). The degree of crystallinity of the coatings was approximately 13.2%. EIS analysis showed that the electrode annealed at 360°C exhibited the highest specific capacitance, which was much higher than that of the electrode annealed at 340°C (which had a purely amorphous structure) as well as those of the electrodes annealed at 380°C and 400°C (which had higher degrees of crystallinity). On the basis of the obtained results, the following conclusion can be drawn: oxide coatings prepared at temperatures slightly higher than the crystallization temperature of the oxide and containing conductive nanocrystalline particles exhibit the best capacitive performance. We suggest that this phenomenon can be explained by the fact that the electronic conductivity of the coating is greatly improved by the presence of the homogeneously distributed conductive nanocrystalline particles in the amorphous matrix. Furthermore, the protonic conductivity and loose atomic configuration of the amorphous structure of the electrode are not adversely affected by the annealing treatment.