Room Temperature Ferroelastic Creep Behavior of Porous (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ

Abstract

The time-dependent deformation of porous (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) under constant uniaxial compressive stress at room temperature has been studied. Both axial and lateral stress–strain deformation curves clearly show the non-linear ferroelastic behavior of LSCF perovskite during compression. The ferroelastic characteristics of deformation curves such as coercive stress and apparent loading moduli decrease when the porosity of the samples increases. Ferroelastic creep deformations at applied stresses of 25 and 50 MPa demonstrate that stress and porosity are influencing factors on creep deformation, which increases with increasing stress and porosity. A negative creep or axial expansion and lateral contraction were observed in the sample with 35% porosity under 50-MPa constant compression stress.

Time dependent deformation of LaCoO3 based perovskites at different temperatures: ferroelastic and non-ferroelastic creep behaviour

“…In this equation, two creep parameters, the characteristic time τ and the equilibrium strain increment normalΔϵeq, were used to describe the creep strain at room temperature. Slightly modified Prony series’ empirical equations were used to describe room temperature uniaxial ferroelastic creep in [16,21], however, their approach required a number of empirical parameters to fit experimental time-dependent deformation behaviour of La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ based perovskites. The high-temperature non-ferroelastic creep strain was detected in LaCoO 3 in four-point bending testing in [22], however, no detailed analysis of high temperature time dependent phenomenon in LaCoO 3 was performed at that time.…”

“…It was reported that these materials, such as LaCoO 3 , LaFeO 3 , LaMnO 3 or LaCrO 3 based perovskites, are ferroelastic and hysteretic upon mechanical loading due to the mobility of their defects, such as domain walls, stacking faults, multiple point defects among others [5][6][7][8][9][10][11][12]. Such defect mobility upon application of stress results in time-dependent continuous deformation that easily occurs in these perovskites even at room temperature [13][14][15][16]. Such room temperature ferroelastic creep is distinctly different from non-ferroelastic creep that mainly occurs in materials at high temperatures due to grain sliding, dislocation movements or even diffusion of atoms upon applied stress [17][18][19].…”

“…Such room temperature ferroelastic creep is distinctly different from non-ferroelastic creep that mainly occurs in materials at high temperatures due to grain sliding, dislocation movements or even diffusion of atoms upon applied stress [17][18][19]. While high-temperature non-ferroelastic creep experiences primary, secondary and tertiary stages of deformation at constant applied stress, the ferroelastic creep is characterised by ever decreasing slope of the creep curve, which mostly resembles the primary stage of high-temperature non-ferroelastic creep [13,16]. It is generally accepted that in these materials ferroelastic creep deformation prevails at room temperature, while the non-ferroelastic component at room temperature is generally small and can be considered negligible.…”