Preparation of Doped Spinel Cobalt Oxide Thin Films and Evaluation of their Thermal Stability

Abstract

Spinel cobalt oxide doped with nickel and zinc are deposited using a CVD reactor equipped with a pulsed spray evaporation system. This process allows easy control of the film composition through the adjustment of the composition of the liquid feedstock; a linear dependence is observed in both cases. Doped spinels with atomic ratios of doping-metal to Co ranging from 0 to 0.5 are deposited and subjected to various surface characterization methods. Zinc as a doping metal, which nonselectively occupies the octahedral and the tetrahedral sites, preserves the cubic spinel structure; in contrast, nickel, which preferably occupies the octahedral sites, preserves the cubic structure only up to Ni/Co = 0.14 and then induces a tetragonal distortion. This disordered structure allows more polarons, and therefore presents a conductivity which increases substantially with the concentration of nickel in the deposited films. The thermal stability of cobalt oxide is maintained in the case of nickel doping as long as the cubic structure is preserved, and then decreases continuously with the concentration of nickel doping once the tetragonal deformation is induced. An upper thermal stability limit as low as 350°C is observed for films with Ni/Co = 0.33. In contrast, zinc steadily improved the thermal stability with increased doping concentration, and reaches ∼850°C, which is 200°C higher than that of pure cobalt oxide.

In situ Fourier Transform Infrared Spectroscopy Diagnostic for Characterization and Performance Test of Catalysts

“…Be- yond 600 • C, there is a progressive loss of crystallinity resulted from the broadening of the spinel bands. At 650 • C, the spinel gradually releases its oxygen lattice to form CoO, with the characteristic band in the range of 700−800 cm −1 , demonstrating that Co 3 O 4 can be thermally stable at 650 • C. CoO is the only phase observed above 700 • C. These thermal stability limits fit well with earlier observations on mixed oxides with Co 3 O 4 as one of the limiting systems [34].…”

Binderless Solution Processed Zn Doped Co3O4 Film on FTO for Rapid and Selective Non‐enzymatic Glucose Detection

“…Noble metals such as, Ag, Au, Pt and Pd have been reported to enhance sensor response and selectivity . Addition of Ni and Zn as a dopant in Co 3 O 4 increases the electrical conductivity and decreases resistivity . However, the application of Zn doped Co 3 O 4 material has been scarcely reported in glucose detection application.…”

Synthesis of Nanosized Zinc‐Doped Cobalt Oxyhydroxide Parties by a Dropping Method and Their Carbon Monoxide Gas Sensing Properties

“…e results also showed that Au nanoparticles enhance the reaction kinetics at low temperature. In addition, Bahlawane et al [15] indicated that the addition of nickel or zinc affects the conductivity of Co 3 O 4 , generating metal vacancies and decreasing resistivity. Similar results for the addition of SnO 2 to Co 3 O 4 sensor materials were reported [16].…”