Synthesis and characterization of LTCC composites based on the spodumene/anorthite crystallizable glass

► Low-loss LTCC composite is fabricated by spodumene glass and anorthite glass. ► Densified composite is achieved despite its component's poor densification. ► A two-stage viscous flow sintering densification mechanism is proposed. ► Mutual diffusion between the glasses kept tan δ of the composites within 0.005. ► TEC of the composites is in the range of 2.8-5.4 ppm/°C.