Preparation and properties of LiMgPO4 and its composites using cold sintering process

LiMgPO₄ (LMP) ceramics and (1-x)LMP-xPTFE inorganic-organic composites were successfully prepared using the cold sintering process. The effects of different uniaxial pressures (300-600 MPa), sintering temperatures (160-200 °C), and holding times (30-90 min) on the microstructure and properties of the ceramics were systematically investigated. The results indicate that under the conditions of 600 MPa, 200 °C, and 30 min, the LMP ceramics achieved a relative density of 93.1% and exhibited optimal microwave dielectric properties: ε_r = 5.12, and tanδ = 6.87×10⁻³ (1 MHz). Systematic investigation of the cold sintering process parameters revealed that within certain ranges, increased uniaxial pressure and elevated sintering temperature both promote ceramic densification, while appropriate holding time facilitates grain growth, though excessive duration hinders the densification process. To further enhance the performance of LMP ceramics for substrate applications, (1-x)LMP-xPTFE inorganic-organic composites were fabricated under these optimized conditions. The composite with x = 0.4 exhibited optimal microwave dielectric properties: ε_r = 2.80, Q×f = 9711 GHz, and τ_f = −39.84 ppm/°C.