Controllable τf value of barium silicate microwave dielectric ceramics with different Ba/Si ratios

Ba1+1/M[Si2O5+1/M] low‐permittivity microwave dielectric ceramics are prepared using the conventional solid‐state method. Pure phases are obtained in barium silicates with M = 1, 3, 4, 5, and ∞, except for M = 7, in which two phases, Ba5Si8O21 and BaSi2O5, are observed. As the complexity of the crystal structure described by the Shannon information per reduced unit cell increases, the τf value tends to change from a negative to a positive value, except for M = 5, which has the highest complexity. A single Ba5Si8O21 phase with εr anomaly peak at −180°C exhibits a rare positive τf value (+25 ppm/°C), which is a novel temperature compensator.