Particle atomic layer deposition of alumina for sintering yttria‐stabilized cubic zirconia

O’Toole, Rebecca J.; Bartel, Christopher J.; Kodas, Maila U.; Horrell, Alexa J.; Ricote, Sandrine; Sullivan, Neal P.; Gump, Christopher J.; Musgrave, Charles B.; Weimer, Alan W.

doi:10.1111/jace.16091

Cited by 9 publications

(18 citation statements)

References 48 publications

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“…(A) EDS and (B) high‐resolution TEM of 9ALD (figure from a previous publication 29 ). [Color figure can be viewed at wileyonlinelibrary.com]…”

Section: Resultsmentioning

confidence: 99%

“…The microstructures of samples from current‐rate flash experiments were characterized by SEM and TEM. Average grain size measurements for flash‐sintered samples range from 0.49 to 1.19 μm (Table 2), much less than ~3 μm for materials processed by conventional sintering to similar final densities 29 . Note that 0.7 wt% Al 2 O 3 (1ALD) enhances grain growth relative to 0ALD, for both 40 mA mm −2 min −1 and 120 mA mm −2 min −1 experiments.…”

Section: Resultsmentioning

confidence: 99%

“…To test the hypothesis that the densification of a given sample is controlled by the same diffusion mechanism during both flash and conventional sintering, the sintering rate equation 27,28 (Equation ) can be used:

{(\frac{d ρ}{d t} = \frac{A f (ρ)}{T d^{n}} \exp (‐ \frac{Q}{italicRT})|}_{{\frac{normald ρ}{normald t}}_{max}}

where dρ/d t is the densification rate, A is a material‐dependent constant, f (ρ) is a function of density, d is the grain size, n is the grain size power law, Q is the activation energy of sintering, and R is the ideal gas constant. To determine dρ/d t , the densification curves for both the flash and conventionally sintered 29 0‐9ALD samples were fit to a sigmoid function to determine ρ( t ) and numerically differentiated (Figure 9). Assuming the mechanism of densification is the same for both conventional and flash sintering (i.e., n and Q are constants) and A , f (ρ), and d are approximately constant for a given sample type, the ratio of Equation evaluated for both flash and conventional sintering at the maximum densification rates ((dρ/d t ) max ) is as follows:

\frac{{(\frac{normald ρ}{normald t})}_{flash, max}}{{(\frac{normald ρ}{normald t})}_{conv, max}} = \frac{T_{conv, max}}{T_{flash, max}} \exp (‐ \frac{normalQ}{normalR} * (\frac{1}{T_{flash, max}} ‐ \frac{1}{T_{conv, max}}))

where (dρ/d t ) flash,max is the maximum densification rate during flash sintering at temperature T flash,max , and (dρ/dt) conv,max is the maximum densification rate during conventional sintering at temperature T conv,max .…”

Section: Discussionmentioning

confidence: 99%

“…8YSZ powder was purchased from Tosoh (TS‐8Y, >99.7 wt% ZrO 2 + HfO 2 + Y 2 O 3 , 12.7 m 2 /g specific surface area, 25 nm crystallite size) and was coated with 0, 1, 5, or 9 cycles of Al 2 O 3 ALD (referred to as 0‐9ALD) in a fluidized bed reactor 31,32 . Experimental details for the particle ALD of Al 2 O 3 onto 8YSZ powders and subsequent powder characterization (inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), high‐resolution transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS)) can be found in a previous publication 29 . Additionally, 8YSZ powder was mechanically mixed with α‐Al 2 O 3 nanopowder (Inframat Advanced Materials, ~100 nm particle size) and ethanol in a roller mill for 35 hours with a 10:1 media to powder ratio to produce a mechanically mixed sample with an equivalent Al 2 O 3 content as 5ALD (2.2 wt%, referred to as 5MIX).…”

Section: Methodsmentioning

confidence: 99%

“…The effect of this addition on voltage‐to‐current control and current rate experiments is studied. These results from flash are compared with conventional sintering of these coated powders where the ALD coating has been shown to enhance densification and hinder grain growth 29 …”

Section: Introductionmentioning

confidence: 99%

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Flash sintering of yttria‐stabilized zirconia powders coated with nanoscale films of alumina by atomic layer deposition

et al. 2021

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The addition of small quantities of aluminum oxide (Al2O3) to 8 mol% yttria‐stabilized zirconia (8YSZ) benefits conventional sintering by acting as a sintering aid and altering grain growth behavior. However, it is uncertain if these benefits observed during conventional sintering extend to flash sintering. In this work, nanoscale films of Al2O3 are deposited on 8YSZ powders by particle atomic layer deposition (ALD). The ALD‐coated powders were flash sintered using voltage‐to‐current control and current rate experiments. The sintering behavior, microstructural evolution, and ionic conductivities were characterized. The addition of Al2O3 films changed the conductivity of the starting powder, effectively moving the flash onset temperature. The grain size of the samples flashed with current rate experiments was ~65% smaller than that of conventionally sintered samples. Measurement of grain size and estimates of sample density as a function of temperature during flash sintering showed that small quantities of Al2O3 can enhance grain growth and sintering of 8YSZ. This suggests that Al2O3 dissolves into the 8YSZ grain boundaries during flash sintering to form complexions that enhance the diffusion of species controlling these processes.

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“…(A) EDS and (B) high‐resolution TEM of 9ALD (figure from a previous publication 29 ). [Color figure can be viewed at wileyonlinelibrary.com]…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

{(\frac{d ρ}{d t} = \frac{A f (ρ)}{T d^{n}} \exp (‐ \frac{Q}{italicRT})|}_{{\frac{normald ρ}{normald t}}_{max}}

\frac{{(\frac{normald ρ}{normald t})}_{flash, max}}{{(\frac{normald ρ}{normald t})}_{conv, max}} = \frac{T_{conv, max}}{T_{flash, max}} \exp (‐ \frac{normalQ}{normalR} * (\frac{1}{T_{flash, max}} ‐ \frac{1}{T_{conv, max}}))

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flash sintering of yttria‐stabilized zirconia powders coated with nanoscale films of alumina by atomic layer deposition

et al. 2021

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A new holder/container with a porous cover for atomic layer deposition on particles, with transport analysis and detailed characterization of the resulting materials

Shah

Patel

Major

et al. 2020

Surface & Interface Analysis

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Atomic layer deposition (ALD) is widely used in the semiconductor and materials industries for depositing thin films. Here, we describe a holder/container for performing ALD on particles that does not require agitation. This device contains a broad, shallow, circular recess that holds the particles. Two different frits and combinations of stacked meshes were explored as a cover to this holder to restrict the movement of the particles while still allowing good conductance of the ALD reagent gases. A mathematical discussion of the diffusion through the frits and stacked meshes is presented. As confirmed by spectroscopic ellipsometry (SE) on planar witness silicon shards, consistent, high‐quality film growth took place inside and outside the holder. The performance of the holder was demonstrated with ~5‐μm zirconia particles that were coated with alumina from trimethylaluminum (TMA) and water, and with zinc oxide from diethylzinc (DEZ) and water. Deposition on different amounts of particles was investigated (50, 100, 200, and 500 mg). Parasitic chemical vapor deposition (CVD) appeared to be present when a greater number of particles or meshes were used. ALD coating on particles was also confirmed by X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and energy‐dispersive X‐ray spectroscopy (EDS).

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Particle atomic layer deposition

Weimer

2019

J Nanopart Res

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The functionalization of fine primary particles by atomic layer deposition (particle ALD) provides for nearly perfect nanothick films to be deposited conformally on both external and internal particle surfaces, including nanoparticle surfaces. Film thickness is easily controlled from several angstroms to nanometers by the number of self-limiting surface reactions that are carried out sequentially. Films can be continuous or semi-continuous. This review starts with a short early history of particle ALD. The discussion includes agitated reactor processing, both atomic and molecular layer deposition (MLD), coating of both inorganic and polymer particles, nanoparticles, and nanotubes. A number of applications are presented, and a path forward, including likely near-term commercial products, is given.

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Particle atomic layer deposition of alumina for sintering yttria‐stabilized cubic zirconia

Cited by 9 publications

References 48 publications

Flash sintering of yttria‐stabilized zirconia powders coated with nanoscale films of alumina by atomic layer deposition

Flash sintering of yttria‐stabilized zirconia powders coated with nanoscale films of alumina by atomic layer deposition

A new holder/container with a porous cover for atomic layer deposition on particles, with transport analysis and detailed characterization of the resulting materials

Particle atomic layer deposition

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