No abstract

Ceria rare earth solid solutions are known as solid electrolyte with potential application in oxygen sensors and solid oxide fuel cells. We report the preparation of gadolinia-doped ceria, Ce 0.90 Gd 0.10 O 1.95 , by the conventional solid-state reaction method and the preparation of thin films from a sintered pellet of gadolinia-doped ceria by the pulsed laser deposition technique. The effect of process conditions, such as substrate temperature, oxygen partial pressure, and laser energy on microstructural properties of these films are examined using powder X-ray diffraction, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy.

Pulsed laser deposition is a technique that is capable of producing high quality multicomponent films under a broad range of ambient conditions. This technique has been widely used to grow thin films of numerous compounds. In particular, it enables the growth of films in reactive environments such as oxygen and nitrogen. Pulsed laser deposition of novel oxides such as cerium oxide (CeO 2 ), Gd doped cerium oxide (GDC) and La-Sr-Ga-Mg-O (LSGM) on (111) Si, (100) MgO, (100) YSZ and (012) sapphire substrates is demonstrated. A systematic study on the influence of the substrate temperature and substrate orientation on the growth characteristics of these oxides is reported.

Microstructural properties of nano-ionic thin films of gadolinia-doped ceria (GDC) prepared by pulsed laser ablation from sintered targets of gadolinia (5-20 mol%) doped ceria are investigated. The ionic conductivity measurements of the sintered pellets showed a decrease in the activation energy from 1.1 to 0.65 eV for 5 and 30 mol% gadolinia-doped ceria, respectively. The microstructural properties of the GDC films as a function of substrate temperature, oxygen partial pressure, and laser energy show that the films are polycrystalline in the entire range of substrate temperature. The grain size is found to increase with increasing temperature up to 873 K. Further improved crystallinity is noticed for the films grown with oxygen partial pressure of 0.1-0.2 mbar. X-ray diffraction and transmission electron microscopy (TEM) reveal nanocrystalline grains with textured growth along <111> orientation in these films at low substrate temperature and at lower oxygen partial pressure. TEM study shows a uniform distribution of nanocrystal of 8-10 nm for energies ≤200 mJ/pulse, and nanocrystals embedded in a large crystalline matrix of doped ceria for energies in the range 400-600 mJ/pulse. Raman spectroscopy also confirms the defects in these films. The study also reveals that the substrate temperature and oxygen partial pressure could influence preferred orientation, while the laser energy could significantly influence defect concentration in these films.