Crystal structure dependence of the microstructure and microwave dielectric properties of (SrxCa1−x)(Zr0.95Ti0.05)O3 (0 ≤ x ≤ 1) perovskite ceramics

Abstract

A solid-state reaction process has been used to fabricate (Sr_xCa_1−x)(Zr_0.95Ti_0.05)O₃ (0 ≤ x ≤ 1) ceramics, and the crystal structure dependence of the microstructure and microwave dielectric properties has been investigated. The grain boundary migration is hindered and the grain size decreases with the increase of x. The crystal structure changes from the orthorhombic phase to the coexisting orthorhombic–cubic phase when x ≥ 0.55. A coherent phase interface is formed at the orthorhombic–cubic phase transition interface, indicating that the two phases have similar lattice structures and a slight mismatch in crystal cell parameters. The short-range ordered reconstructed superlattice structure is driven by the interface strain near the coherent phase interface. From x = 0.55 to x = 1, the Q × f values increase obviously, which indicates that the short-range ordered superlattice structure reduces the intrinsic loss of ceramics. The Raman spectra also verify the above deduction and show that the ceramics with reconstructed superlattices have smaller lattice vibration anharmonicity. Due to cubic phase regulating τ_f and reconstructed superlattice reducing dielectric loss, the SrZr_0.95Ti_0.05O₃ (x = 1) sample has the best microwave dielectric properties with ε_r = 36.4, Q × f = 26 300 GHz, and τ_f = −2.5 ppm °C⁻¹, and the Q × f value is twice as high as the maximum value (13 600 GHz) of pure SrZrO₃ ceramics reported in the literature. This work not only provides a new option for low-cost and high-performance intermediate dielectric constant ceramics, but also proposes a new design method to improve the microwave dielectric properties of perovskite ceramics.