ジルコン合成の反応速度に及ぼす添加剤の影響

抄録

A study was made of the effect of additives on the high-temperature synthesis of zircon from zirconia and silica.
The silica used in this test was chemically pure being about 99.8%. It was identified by X-ray analyses as α-quartz. The zirconia used was about 99.9% and in the monoclinic form. Its X-ray analyses and differential thermal analyses were made in the synthesis test. The crystallographic forms present and their proportions were determined in all cases by X-ray analyses of the cooled specimens. The effects of additions of various additives on the rate of synthesis of zircon were evaluated and may be summarized as follows:
(1) CuO, PbO, CdO and V₂O₅ are effective on the degree of synthesis of zircon as shown in Table I.
(2) The minimum temperature at which zircon can be synthesized is about 1000°C in the presence of large amounts of CuO, PbO or CdO respectively. At 1100°C there are definite indications of synthesis in all three cases.
(3) The higher the additive oxide content, the more complete is this reaction at the same rate of time and at the same temperature.
(4) Cu⁺⁺ or Cu⁺ is present in quartz at about 1000°C, and the formation of PbSiO₃ melts and CdSiO₃ accelerates the quartz-cristobalite transformation. The formation of cristobalite may effectively increase the speed of the reaction between silica and zirconia.