# Low temperature densification behaviour of metastable phases in $ZrO_2–Al_2O_3$ powders produced by spray pyrolysis

Gandhi, AS and Jayaram, V and Chokshi, AH (2001) Low temperature densification behaviour of metastable phases in $ZrO_2–Al_2O_3$ powders produced by spray pyrolysis. In: Materials Science and Engineering A, 304-30 . pp. 785-789.

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## Abstract

It has been established that powder compacts of amorphous $ZrO_2-Al_2O_3$, prepared by spray pyrolysis, densify up to nearly full density at temperatures below 923 K and above 573 K, when a moderately high pressure of 750 MPa is applied. The samples remain amorphous after hot pressing. Densification behaviour has been studied in the composition $ZrO_2-40$ mol% $Al_2O_3$ with particle sizes in the ranges 15–35, 3–15 and below $3\mu m$. Temperatures of 573, 723 and 873 K were used along with applied pressures of 250, 500 and 750 MPa. The fine particle size led to a maximum final relative density of 96.5%. Pressure is the dominant variable in densification once the temperature is above a minimum of 573 K. Time dependent densification is relatively insignificant. Particle rearrangement at low pressures and deformation and fracture at high pressures are likely to be responsible for the high relative densities between 84 and 92 obtained during pressurising the various particle sizes up to 750 MPa. Hot pressing of composition with 62 mol% $Al_2O_3$ at 873 K, 750 MPa led to a final density of 99.6%, indicating that higher $Al_2O_3$ content imparts greater sinterability to the amorphous phase.

Item Type: Journal Article Copyright of this article belongs to Elsevier. Low temperature densification; Amorphous ZrO2–Al2O3; Spray pyrolysis Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) 16 Mar 2007 19 Sep 2010 04:36 http://eprints.iisc.ernet.in/id/eprint/10417