Densification of porous 8 mol% yttria-stabilized zirconia component: modelling and experimental studies

Abstract

In this paper, the densification of a ceramic powder matrix that contained large macropores of the size much larger than the average grain size of the matrix was studied. The grain-boundary diffusion controlled sintering models of ceramic matrix contained large macropores were first established. A sintering potential associated with the macropores was also verified and introduced into the models. The experimental data were collected for the sintering of porous 8 mol% yttria-stabilized zirconia system with 20 vol% large pores. The predictions of the model were found in good agreement with experimental data.

Appendix. Volume fraction of large pores in a macroporous system

The density of the overall macroporous body, ρ, can be obtained by measuring the volume and mass of the samples, and can be written as

$$ \rho = {\frac{{V_{d} }}{{V_{bp} + V_{sp} + V_{d} }}} $$

(31)

where V_d is the volume of the dense part, V_bp is the volume of the large pores and V_sp is the volume of the small micropores.

The density of the microporous matrix in the macroporous system, ρ_m, can be expressed as

$$ \rho_{m} = {\frac{{V_{d} }}{{V_{sp} + V_{d} }}} $$

(32)

ρ_m can be obtained from the SEM micrographs of the cross section of the specimens.

The volume fraction, f_v, of the large macropores can be expressed as

$$ f_{v} = {\frac{{V_{bv} }}{{V_{sp} + V_{d} + V_{bp} }}} $$

(33)

From Eqs. 31 and 32, Eq. 33 can be expressed in terms of ρ and ρ_m as

$$ f_{v} = 1 - \left( {1 + {\frac{{1 - \rho_{m} }}{{\rho_{m} }}}} \right)\rho $$

(34)