Properties of CaTi1 ? xFexO3 ? ? Ceramic Membranes

Abstract

CaCO 3 , TiO 2 and Fe 2 O 3 were mixed in the appropriate stoichiometric quantities and calcined at 1100 • C for 10 h. These powder mixtures were uniaxially pressed and sintered at temperatures ranging from 1350 to 1500 • C for 2 h in order to obtain dense disk-shaped samples with nominal CaTi 1−x Fe x O 3−δ (x = 0.05, 0.15, 0.20, 0.40 and 0.60) compositions. Dilatometry and in situ high temperature powder X-ray diffraction analysis showed a good agreement on the thermal expansion behaviour of these materials between room temperature and 1000 • C. The estimated linear thermal expansion coefficient is close to 13 × 10 −6 K −1 and is little affected by composition. No evidence for surface carbonation was detected in the infrared spectra collected on samples previously annealed in CO 2 atmospheres. The oxygen permeability measured at temperatures ranging from 750 to 1000 • C goes through a sharp maximum for x = 0.20. This result is interpreted by structural differences related to change from disordered to ordered oxygen vacancies. The overall performance of CaTi 0.80 Fe 0.20 O 3−δ is compared to other mixed conducting materials.

Effect of temperature on the electrical properties of nanocrystalline CaTi1−x Fe x O3−Δ perovskite

“…These might be considered as colossal effect, which is due to the microstructural changes resulting from the isotropic and anisotropic thermal expansions of the materials [11,12]. The CaTi l-x Fe x O 3-d (CTFO) perovskite electroceramics may assume cubic, tetragonal, or orthorhombic crystal structures, which is influenced primarily by their thermal expansion over a wide range of temperatures ([1000°C) [13][14][15]. Attempts have been made in the past to tailor the charge (electronic and ionic) transport properties of CTFO perovskite.…”

“…Attempts have been made in the past to tailor the charge (electronic and ionic) transport properties of CTFO perovskite. The earlier studies reveal that both temperature and ionic doping levels yield attractive electrical properties because of nonlinear molecular interactions [16][17][18][19].…”

“…Besides, the addition of thermal treatment to this composite enhances oxygen vacancy and charge ordering moments resulting from increased occupancy of Ti 4? states [17,23]. Thus, CTFO with high concentration of dopant iron is suitable for high-temperature applications whereas with low concentration of dopant, it is ideal for low-temperature applications [2,14,24].…”

“…states [17,23]. Thus, CTFO with high concentration of dopant iron is suitable for high-temperature applications whereas with low concentration of dopant, it is ideal for low-temperature applications [2,14,24]. Previously, thermal expansion studies were conducted to discern the characteristics of CTFO such as crystal structure, modulus effect, and yield strength [25][26][27].…”

“…Previously, thermal expansion studies were conducted to discern the characteristics of CTFO such as crystal structure, modulus effect, and yield strength [25][26][27]. For example, the linear thermal expansion coefficient (TEC) of CTFO (&13 9 10 -6 K -1 ) perovskite material has been investigated over a wide range of temperatures (25-1000°C) [14].…”