Designed Y³⁺ Surface Segregation Increases Stability of Nanocrystalline Zinc Aluminate

LES Martin and NM O'Shea and JK Mason and RHR Castro, JOURNAL OF PHYSICAL CHEMISTRY C, 127, 4239-4250 (2023).

DOI: 10.1021/acs.jpcc.2c07353

The thermal stability of zinc aluminate nanoparticles is critical for their use as catalyst supports. In this study, we experimentally show that doping with 0.5 mol % Y2O3 improves the stability of zinc aluminate nanoparticles. The dopant spontaneously segregates to the nanoparticle surfaces in a phenomenon correlated with excess energy reduction and the hindering of coarsening. Y3+ was selected based on atomistic simulations on a 4 nm zinc aluminate nanoparticle singularly doped with elements of different ionic radii: Sc3+, In3(+,) Y3+, and Nd3+. The segregation energies were generally proportional to ionic radii, with Y3+ showing the highest potential for surface segregation. Direct measurements of surface thermodynamics confirmed the decreasing trend in surface energy from 0.99 for undoped to 0.85 J/m(2) for Y-doped nanoparticles. Diffusion coefficients calculated from coarsening curves for undoped and doped compositions at 850 degrees C were 4.8 x 10(-)1(2) cm(2)/s and 2.5 x 10(-12) cm(2)/s, respectively, indicating the coarsening inhibition induced by Y3+ results from a combination of a reduced driving force (surface energy) and decreased atomic mobility.

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