Nd-Ce-TZP Powders and Ceramics: Hydrothermal Preparation of High Quality Powders from Sulphate Precursors
High quality powders of tetragonal zirconia of the composition Nd0.01 Ce0.08 Zr0.91 O2-x have been prepared hydrothermally by in-situ crystallization (best 225°C/2.4 MPa, 7–8 h, pH 10–11) of co-precipitated sulphate derived gels. The best powders contain 0.2 wt% residual SO3. Uniaxially pressed tablets of the as prepared freeze dried powders sinter to >95% TD in 1 hat 1350°C, whereas tablets of calcined and milled powders sinter to >99% TD in 1 h at 1320°C. These ceramics have an average grain size around 1 µm, a 4-point bending strength of 450 MPa, and show a pseudo-plastic behaviour. The toughness is too high to be measured by Vickers indentation. Sintering to 1400°C for 2 h results in sufficient grain growth to induce a slow spontaneous transformation of tetragonal→monoclinic zirconia upon cooling.
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