Sintering and properties of borosilicate glass/Li-Na-K-feldspar composites for electronic applications

Glass/ceramic composites are considered as one of the most important materials for electronic applications. In the present work, an attempt for using Li-Na-K containing feldspar in addition to borosilicate glass to fabricate glass/ceramic composites having good properties was conducted. Firstly, the glass frit was prepared and grinded by high energy ball mill to get nano powder. Then, five designed batches of glass/feldspar composites containing 10, 20, 30, 40 and 50 wt% feldspar were mixed, pressed and sintered at 850 °C. Bulk density and apparent porosity of sintered specimens were determined by Archimedes method. Identification of the formed phases was examined by X-ray diffraction (XRD) analysis. Microstructure of sintered bodies was examined by scanning electron microscope. Microhardness of sintered samples was determined using Vickers indentation technique whereas the fracture toughness was determined by Indentation Fracture (IF) method. The dielectric constant of sintered composites was measured at 1 MHz. The thermal expansion coefficient (TEC) was also measured in the temperature range from room temperature to 1000 °C. The results revealed that Li-Na-K feldspar and borosilicate glass were successfully used to fabricate composites with good electrical properties and thermal expansion suitable for electronic applications. The inhibition of cristobalite amount and the formation of beta spodumene in addition to the quartz were responsible for the improvement of the electrical and thermal properties. The formed amount of beta spodumene was the ideal amount after which the higher amount can cause crack in the body due to the volume change occurred by the differences in thermal expansion of alpha and beta spodumene.