Impurity diffusion of 141Pr in LaMnO3, LaCoO3 and LaFeO3 materials

Abstract

The impurity diffusion of Pr(3+) in dense polycrystalline LaMnO(3), LaCoO(3) and LaFeO(3) was studied at 1373-1673 K in air in order to investigate cation diffusion in these materials. Cation distribution profiles were measured by secondary-ion mass spectrometry and it was found that penetration profiles of Pr(3+) had two distinct regions with different slopes. The first, shallow region was used to evaluate the bulk diffusion coefficients. The activation energies for bulk diffusion of Pr(3+) in LaMnO(3), LaCoO(3) and LaFeO(3) were 126 +/- 6, 334 +/- 68 and 258 +/- 75 kJ mol(-1), respectively, which are significantly lower than previously predicted by atomistic simulations. The bulk diffusion of Pr(3+) in LaMnO(3) was enhanced compared to LaCoO(3) and LaFeO(3) due to higher concentrations of intrinsic point defects in LaMnO(3), especially La site vacancies. Grain-boundary diffusion coefficients of Pr(3+) in LaCoO(3) and LaFeO(3) materials were evaluated according to the Whipple-Le Claire equation. Activation energies for grain-boundary diffusion of Pr(3+) in LaCoO(3) and LaFeO(3) materials were 264 +/- 41 kJ mol(-1) and 290 +/- 36 kJ mol(-1) respectively. Finally, a correlation between activation energies for cation diffusion in bulk and along grain boundaries in pure and substituted LaBO(3) materials (B = Cr, Fe, Co) is discussed.

High temperature X-ray diffraction and thermo-gravimetrical analysis of the cubic perovskite Ba0.5Sr0.5Co0.8Fe0.2O3−δ under different atmospheres

“…The formation of the hexagonal BSCF is most likely limited by diffusion of A-cations since B-cations are reported to be significantly more mobile in related LaMO 3 materials [50][51][52][53][54] . The hexagonal polymorph was not observed to be formed in N 2 and the disappearance of the hexagonal polymorph was shifted to higher temperature in pure O 2 relative to air and 0.01 bar O 2 (see Fig 2a).…”

96Zr Tracer Diffusion in AZrO3 (A = Ca, Sr, Ba)

“…Abbreviations: ppolycrystalline; sc-single crystal; c-cubic; b-bulk; gb-grain boundaries. (1) Ho in p BaTiO3 gb [11]; (2) Ho in p BaTiO3 b [11]; (3) Ni in p Ba(Ho,Ti)O3 [10]; (4) Ni in sc BaTiO3 [10]; (5) Ni in p BaTiO3 [10]; (6) Si in MgSiO3 [39]; (7) 49 Ti in sc (La,Sr)TiO3 [25]; (8) Zr in sc BaTiO3 [12]; (9) 141 Pr in LaFeO3 gb [40; (10) 141 Pr in LaCoO3 gb [40]; (11) Co in LaCoO3 gb [41]; (12) Cr in LaMnO3 [42];(13) Mn in LaCoO3 [43]; (14) Co in LaCoO3 b [41]; (15) 141 Pr in LaMnO3 [40]; (16) Co in GdCoO3 [44]; (17) Co in EuCoO3 [44]; (18) Co in SmCoO3 [44]; (19) Co in NdCoO3 [44]; (20) Co in PrCoO3 [44]; (21) 50 Cr in (La,Ca)CrO3 gb [45]; (22) Co in LaCoO3 [44]; (23) Mn in LaMnO3 b [42]; (24) Mn in LaMnO3 gb [42]; (25) Fe in LaFeO3 gb [46]; (26) Fe in LaFeO3 b [46]; (27) 141 Pr in LaCoO3 b [40]; (28) 141 Pr in LaFeO...…”

134Ba diffusion in polycrystalline BaMO3 (M = Ti, Zr, Ce)

“…13 The Ba lattice diffusion in BaMO 3 compared to the A-site cation diffusion in general in perovskites reported in the literature revealed no apparent trend. [26][27][28][29][30][31][32][33][34][35][36][37][38] In addition, the diffusion mechanisms for the data reported in the literature are usually not described. The point defect chemistry after materials processing determines the dominating diffusion mechanism as shown for BaZrO 3 .…”