Polycrystalline Magnesia

Miles GD, Sambell RAJ, Rutherfo J, Stephens GW (1%7) Fabrication of fully dense transparent polycrystalline magnesia. Trans Br Ceramic Soc 66 319... 

TABLE 8.1 Thermal Conductivity of Polycrystalline Sintered Magnesia... 

You react two samples of alumina and magnesia at 1400°C for 1 hour. This time the MgO is a perfect single crystal but the alumina is 100-nm grain size polycrystalline material. Will the reaction proceed more quickly... 

One implication that has been adequately validated by experiment is that eomplex oxides with low particularly mullite, have creep strengths superior to single-phase oxides, such as alumina, yttria, and magnesia. However, the findings that solid solutions and nanopartieles profoundly affeet ereep rates in bulk polycrystalline oxides was not obvious from... 

Greskovich C, Brewer JA (2001) Solubility of magnesia in polycrystalline alumina at high temperatures. J Am Ceram Soc 84 420-425... 

This material characteristic is referred to as "phase transformation toughening" (Cales 2000). However, the phase-induced volumetric transformation can also have disastrous consequences if not properly controlled. For this reason, the phase transformation property of zirconia is typically stabilized with the addition of magnesia or yttria (Willmann 1998). The most common type of zirconia used in orthopedics is termed Y-TZP, corresponding to yttria stabilized-tetragonal phase, polycrystalline zirconia (Willmann 1998). The chemical composition of Y-TZP is approximately 5.1% yttria (Y2O3) and 93-94% zirconia (Zr02) (Cales 2000). 

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