A method of determining phase-transition temperatures using solar heating

The phase-transition temperatures in oxide systems were determined on the basis of the process of solidification of specimens which were partially melted on the surface in the focus of a solar furnace. In the ZrO/sub 2/-Y/sub 2/O/sub 3/ binary systems, the specimens with intermediate composition were prepared by combined precipitation of zirconium and yttrium hydroxides from nitric acid solutions followed by drying, roasting at 800 C, briquetting, and melting in the solar furnace. The described method of determination of the phase-transition temperatures in the oxide systems on the basis of the surface of the specimens partially melted in the focus of the solar furnace has a number of advantages in comparison with the method of evaluating the temperatures from the radiation of the rotating cavity: it is not necessary to form the cavity with the emissivity properties similar to those of the absolute blackbody; and the oxide melt formed in the course of melting is distributed mainly on the surface of the specimen so that after interrupting the radiation flux the melt solidifies in its entire volume.