Microstructural, mechanical and electrical properties of alumina-doped cubic zirconia (c-ZrO(2))

Tekeli S., Kayis A., Guru M.

JOURNAL OF SOLID STATE ELECTROCHEMISTRY, vol.12, pp.791-797, 2008 (SCI-Expanded) identifier identifier


The effect of Al(2)O(3) content on microstructure, hardness, fracture toughness and electrical conductivity behaviours of c-ZrO(2) ceramics was investigated using high-purity commercial powder of 8 mol% yttria-stabilised c-ZrO(2) doped with up to 10 wt.% Al(2)O(3). XRD results showed that the c-ZrO(2) specimens doped up to 0.3 wt.% Al(2)O(3) revealed no Al(2)O(3) peaks, indicating that Al(2)O(3) was completely solubilised in the c-ZrO(2) matrix. However, when >0.3 wt.% Al(2)O(3) was added, Al(2)O(3) peaks started to appear, showing that overdoped Al(2)O(3) was not solubilised in the c-ZrO(2) matrix. The introduction of Al(2)O(3) significantly enhanced the hardness and fracture toughness of c-ZrO(2). The hardness and fracture toughness increased with increasing Al(2)O(3) content. The maximum hardness and fracture toughness values reached 1,459 +/- 8 kg/mm(2) stop and 2.41 +/- 0.02 MPa/m(1/2) stop, respectively, with the addition of 10 wt.% Al(2)O(3), while these values were 1,314 +/- 11 kg/mm(2) stop and 1.5 +/- 0.03 MPa/m(1/2) stop for undoped c-ZrO(2). The increase of hardness and fracture toughness can be attributed to smaller grain size, the increment of Young's modulus of Al(2)O(3)-doped c-ZrO(2) and different expansion coefficients of c-ZrO(2) and Al(2)O(3) grains. The electrical conductivity of the specimens was measured using a frequency response analyzer in the frequency range of 5-13 MHz and in the temperature range of 300-800 degrees C. It was seen that electrical conductivity slightly increased with increasing Al(2)O(3) content up to 1 wt.%, and further increase in Al(2)O(3) led to a decreased in the conductivity.