Results and discussion Optimization of processing parameters The
The green compacts from granules with different binder contents were cold isostatically pressed (CIP) under 200 MPa. Their pore size distributions are shown in Fig. 4(a). They exhibited only one peak in 20–200 nm excepting that HG-9-91-01 the green compacts with excessive binder, 2.0 and 3.0 wt.%, had another distribution peak at about 35 μm, representing larger pores in them. The 1.0 wt.% binder formed green compact had the smallest pore size distribution centered at about 60 nm. This relatively smaller and more uniform pore size would greatly promote the densification of ceramics during sintering. Fig. 4(b) shows the density change of fabricated ceramics under different stages. The green compacts with 2.0 and 3.0 wt.% PVB showed the lower density, although pituitary gland had little difference after CIP. However, the difference was acutely magnified after vacuum sintering and the fabricated ceramic with 1.0 wt.% binder had the highest density 99.3% under a lower sintering temperature 1700 °C (they all finished densification >1750 °C). This is consistent with the results of SEM, AD/TD of granules and MIP analysis of green compacts. In fact, the fabricated ceramic with 1.0 wt.% binder also had the highest optical transmittance. Therefore, the optimized binder content of PVB is 1.0 wt.%.