Development of low thermal expansion mono crystalline Sr-feldspar phase via Sr-cordierite ceramic/borosilicate glass composite

The present work focuses on fabrication of low thermal expansion monoclinic Sr-feldspar through sintering of Sr-cordierite ceramic/borosilicate glass composite. The prepared composites were sintered between 1200 and 1350 degrees C. Bulk density and apparent porosity of sintered composites were measured according to Archimedes technique. Phase composition and microstructure of sintered composites were tested by X-ray diffraction and scanning electron microscope attached with EDAX unit. Thermal expansion coefficient and dielectric constant of sintered composites were also determined. The results revealed that mono crystalline Sr-feldspar was formed after sintering up to 1350 degrees C especially in the composites that contain higher ceramic content. As indicated from the result of microanalysis conducted by EDAX, the obtained Sr-feldspar was deficient in SiO2 and SrO. In the composites with higher glass content, little amounts of quartz or cristobalite were also formed, depending on the cooling conditions. The sinterability was increased with increasing sintering temperature and decreased with increasing ceramic content. The obtained sintered composites exhibited low thermal expansion coefficient and dielectric constant. The composite that contains 90% ceramic exhibited thermal expansion coefficient 2.533 x 10(-6) degrees C-1 and dielectric constant value 8.42.