Modeling the grain growth kinetics of doped nearly fully dense nanocrystalline ceramics

Abstract

A grain growth model to describe dopant effects on nanocrystalline ceramics is proposed by incorporating the dopant-segregation-dependent grain boundary (GB) energy and the GB mobility subjected to intrinsic drag and pore drag (both affected by dopant segregation) into the parabolic growth formula. The model addresses the common case of residual porosity in grain growth behavior. Taking near-fully dense nanocrystalline lanthanum doped Yttria stabilized Zirconia (La doped YSZ) as the system of study, the grain growth behavior was explored using the model. The substantially suppressed grain growth in La doped YSZ as compared to La-free YSZ could be attributed to the combined effect of thermodynamically reduced GB energy and kinetically reduced GB mobility. Contrary to previous assumptions, the model suggests that, relative to the GB energy overall effect, the effect of the dopant on the GB mobility plays a more significant role in reducing coarsening. Furthermore, model calculation shows that both intrinsic drag and pore drag makes certain

Enhanced Electrochemical Properties of Zr4+-doped Li1.20[Mn0.52Ni0.20Co0.08]O2 Cathode Material for Lithium-ion Battery at Elevated Temperature

“…A small amount of doped Zr ions may form continuous grain boundary phases in the Li 1.20 [Mn 0.52 Ni 0.20 Co 0.08 ]O 2 particles. These continuous grain boundary phases could enhance the mass diffusion transport at grain boundaries, finally promote the grain growth of Li 1.20 [Mn 0.52 Ni 0.20 Co 0.08 ]O 2 26,27 . And the well crystallization will help to ameliorate the electrochemical properties of cathode.…”

Review of thermo‐kinetic correlation during grain growth in nanocrystalline materials

“…For the verification of thermo-kinetic correlation, in addition to the direct proofs which was provided by Peng et al, 56,[62][63][64][65][66][67][68] there have been a few indirect experiment/simulated results to qualitatively support the theory of thermo-kinetic stabilization. Differing from microstructural evolution behavior in metal materials, the grain growth in NC ceramics often occurs together with the densification and it is highly difficult to separate one process from the other.…”

“…The microstructural evolution during heating in ceramics is more complexed, which is influenced not only by the stabilization effects from reduced GB energy, decreased surface energy of pores and intrinsic drag exerted by the solute atoms, but also by the drag effects from the pores. On the base of the parabolic grain growth equation, Krill et al’s GB energy model and the Borisov et al’s thermo‐kinetic correlation, Gong et al 63 derived a thermo‐kinetic equation to describe the grain growth of NC ceramics, that is,where and are GB mobility from the contribution of intrinsic drag and pore drag, respectively, and x s and ρ are the molar fraction of solute at pore surfaces and the relative density, respectively.…”

“…Evolution of grain size as a function of annealing time for NC 12YSZ and 2La10YSZ annealed at 1373 K. The solid and empty squares denote the experimental data while the solid and dashed lines represent the calculated results by the model 63 …”

“…Due to the concurrence of grain growth and densification during sintering for NC ceramics, it would be of very interesting to analyze the coupling thermodynamic and kinetic stabilization effects in the two process. Isothermal grain growth experiment for nanocrystalline 12 mol% Y 2 O 3 -88 mol% ZrO 2 (12YSZ) and 2 mol% La 2 O 3 -10 mol% Y 2 O 3 -88 mol% ZrO 2 (2La10YSZ) were performed at 1373 K. 63 X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to measure the grain size, whose evolution upon the annealing time were shown in Figure 8. Obviously, significant grain growth occurred for 12YSZ, whose grain size is more than 150 nm at the time of 48 hours, while for 2La10YSZ system, the grain size is far less than that for 12YSZ at the same sintering time.…”