LITHIA PORCELAINS AS PROMISING BREEDER CANDIDATES .1. PREPARATION ANDCHARACTERIZATION OF BETA-EUCRYPTITE AND BETA-SPODUMENE PORCELAIN

beta-Eucryptite, beta-spodeumene and solid-solution porcelain were pre pared by the conventional ceramic technique with three lithia:alumina: silica (LAS) ratios, 1:1:2, 1:1:3 and 1:1:4. The optimization of the c eramic parameters was assessed through measuring their vitrification p arameters with firing temperatures in the range 1000-1350 degrees C. S tructural characterization of the bodies obtained at optimum condition s were followed through X-ray diffraction (XRD) and infrared (IR) spec tral analyses. Thermal dilation up to 1000 degrees C was measured. Mor phological variations were examined through scanning electron microsco py (SEM) of fractured surfaces, as well as selected area electron diff raction (SAED). Results proved that the change from beta-eucryptite wi th 1:1:2 LAS through its solid solution to beta-spodumene with 1:1:4 L AS, i.e. from hexagonal to tetragonal structures, need a firing temper ature of 1320 degrees C. Shifts in XRD lattice planes were complemente d by parallel shifts in IR bands specific for silicates around 1100 cm (-1). Unique negative thermal expansion up to 1000 degrees C for beta- eucryptite changed to the positive value only after 600 degrees C for beta-spodumene. Characteristic large grains were detected in both beta -eucryptite and beta-spodumene micrographs parallel with the polycryst alline rings of the SAED figures. On the other hand, the beta-eucrypti te solid-solution body has smaller grain size with higher glassy phase shown by the larger SAED halo. The present results illuminate the imp ortance of assessing the detailed structural features for future radia tion damage studies. (C) 1997 Elsevier Science Limited and Techna S.r. l.