Lithia porcelains as promising breeder candidates — I. Preparation and characterization of β-eucryptite and β-spodumene porcelain

Abstract

β-Eucryptite, β-spodeumene and solid-solution porcelain were prepared 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 ceramic parameters was assessed through measuring their vitrification parameters with firing temperatures in the range 1000–1350 °C. Structural characterization of the bodies obtained at optimum conditions were followed through X-ray diffraction (XRD) and infrared (IR) spectral analyses. Thermal dilation up to 1000 °C was measured. Morphological variations were examined through scanning electron microscopy (SEM) of fractured surfaces, as well as selected area electron diffraction (SAED). Results proved that the change from β-eucryptite with 1:1:2 LAS through its solid solution to β-spodumene with 1:1:4 LAS, i.e. from hexagonal to tetragonal structures, need a firing temperature of 1320 °C. Shifts in XRD lattice planes were complemented by parallel shifts in IR bands specific for silicates around 1100 cm −1. Unique negative thermal expansion up to 1000 °C for β-eucryptite changed to the positive value only after 600 °C for β-spodumene. Characteristic large grains were detected in both β-eucryptite and β-spodumene micrographs parallel with the polycrystalline rings of the SAED figures. On the other hand, the β-eucryptite solid-solution body has smaller grain size with higher glassy phase shown by the larger SAED halo. The present results illuminate the importance of assessing the detailed structural features for future radiation damage studies.