Na2ZrO3-Al2O3系及びβAl2O3-ZrO2系に関する研究

The decomposition of Na2ZrO3, sinterability, mineralogical composition and expansion of sintered body of the Systems Na2ZrO3-Al2O3 and β Al2O3-ZrO2 were studied. The results obtained are summarized as follows:(1) The decomposition of Na2ZrO3 is promoted by the addition of Al2O3 and even at 1000°C Na2ZrO3 decomposes. At 1200°C Na2O produced by the decomposition reacts partially with Al2O3 to form β Al2O3, but the larger parts of Na2O vaporize. The amount of Na2O absorbed as β Al2O3 increases up to 1400°C and above the temperature it decreases due to the decomposition of β Al2O3. Even at 2000°C, however, β Al2O3 still remains without decomposition.(2) The good sintered body can be obtained with easy by starting the mixture of the system Na2ZrO3-Al2O3. In the sintered body a Al2O3, β Al2O3 and ZrO2 are comfirmed by X-ray analysis.(3) The liquidus boundary in the region of small amounts of Na2O seems to exist near the curve joining the points 45% Al2O3, 55% ZrO2 and 3.12% Na2O, 66.94% Al2O3, 29.94% ZrO2.(4) In the mixture of β Al2O3-ZrO2 a part of β Al2O3 decomposes to produce α Al2O3 during heating, but its larger parts remain in the sintered body without decomposition. The expansion of the sintered body is small as shown in Fig. 7 and 8. Its volume change caused by the transformation of ZrO2 phase remarkably decreases with the addition of β Al2O3.