Effect of the spark plasma sintering parameters, LiF additive, and Nd dopant on the microwave dielectric and optical properties of transparent YAG ceramics

Not only the optical properties, but the microwave dielectric properties of Yttrium aluminium garnet (Y3Al5O12, YAG) ceramics prepared by co-precipitation method combined with spark-plasma sintering (SPS) were investigated by means of adjusting the factors of LiF additive, Nd dopant, and SPS process parameters. Results showed that the in-line transmittance of YAG ceramic with LiF sintered at 1360 °C was 81.8% in the infrared range. With increased sintering temperature, the quality factor (Q × f) and dielectric constant (εr) values of the pure YAG ceramics increased to the maximum and then decreased. The optimal microwave dielectric properties (Q × f = 89,810 GHz, εr = 10.63 and τf = −51.4 ppm/°C) are achieved for transparent YAG ceramics sintered at 1360 °C. The Q × f values of Nd:YAG ceramics were lower than those of the pure YAG ceramics. The optimal microwave dielectric properties of 2 at.%Nd:YAG ceramic cylinder can be obtained with the Q × f of 64,026 GHz, εr of 10.2 and τf of −64.8 ppm/ °C.