Mechanical Properties of Magnesia‐Doped Lanthanum Chromite versus Temperature

Abstract

Magnesia-doped lanthanum chromite is a potential material for use in solid oxide fuel cells as an interconnector due to its resistance to oxidation and reduction. The strength and toughness of La(Cr,,Mg,,,)O, were measured from 25" to 1000°C in the as-fired reduced state and after oxidation. The as-fired samples showed a peak in toughness of approximately 3.9 MPaem"' at 125°C which decreased to approximately 1.4 MPa.m"' at 600°C and 2.8 MPa-m"' at room temperature. This peak in toughness is hypothesized to be due to the rhombohedral-to-orthorhombic phase transition by a toughening mechanism that is currently being investigated. The strength was also affected by the phase transition for both the as-fired reduced and the oxidized samples.

Mechanical properties of LaFeO3 ceramics

“…15,17 The bend strength and fracture toughness of orthorhombic perovskites tends to be constant or increase with temperature, followed by a decrease above the orthorhombic to rhombohedral phase transition temperature. [15][16][17][18][19] The room temperature four-point bending strength of rhombohedral and cubic perovskites has been reported in the range 100-160 MPa. 20,22 The strength of rhombohedral and cubic perovskites generally decreases with increasing temperature, 15,22,23 but the opposite behaviour has also been observed.…”

“…[15][16][17][18][19] The room temperature four-point bending strength of rhombohedral and cubic perovskites has been reported in the range 100-160 MPa. 20,22 The strength of rhombohedral and cubic perovskites generally decreases with increasing temperature, 15,22,23 but the opposite behaviour has also been observed. 24 The fracture toughness of cubic and rhombohedral perovskites tends to be lower (K IC = 1.3-2.2 MPa m 1/2 at room temperature) 21,25 than for orthorhombic materials and generally decreases or remains approximately constant with increasing temperature.…”

“…[12][13][14] So far only limited information is available on the temperature dependency of the mechanical properties of perovskite materials. Typical values for the room temperature four-point bending strength of orthorhombic perovskites lie in the range 100-140 MPa, 15,16 whereas the fracture toughness, K IC , is generally in the range 2.0-2.8 MPa m 1/2 . 15,17 The bend strength and fracture toughness of orthorhombic perovskites tends to be constant or increase with temperature, followed by a decrease above the orthorhombic to rhombohedral phase transition temperature.…”

“…Typical values for the room temperature four-point bending strength of orthorhombic perovskites lie in the range 100-140 MPa, 15,16 whereas the fracture toughness, K IC , is generally in the range 2.0-2.8 MPa m 1/2 . 15,17 The bend strength and fracture toughness of orthorhombic perovskites tends to be constant or increase with temperature, followed by a decrease above the orthorhombic to rhombohedral phase transition temperature. [15][16][17][18][19] The room temperature four-point bending strength of rhombohedral and cubic perovskites has been reported in the range 100-160 MPa.…”

“…24 The fracture toughness of cubic and rhombohedral perovskites tends to be lower (K IC = 1.3-2.2 MPa m 1/2 at room temperature) 21,25 than for orthorhombic materials and generally decreases or remains approximately constant with increasing temperature. 15,17,25 Monolithic ceramics are usually brittle and show elastic behaviour when stress is applied. Some ceramics show non-elastic behaviour and have been termed ferroelastic by analogy with the stress-strain relationship with polarization of a ferroelectric material in an electric field and the magnetization of a ferromagnetic material in magnetic fields.…”