The structure evolution, dielectric properties, and tunable mechanism of (Ba_0.91Ca_0.09)(Zr_yTi_1−y)O₃ ceramics

(Ba_0.91Ca_0.09)(Zr_yTi_1−y)O₃ (0.10 ≤ y ≤ 0.25) ceramics were prepared to study the influence of Zr⁴⁺ content on the structure evolution, dielectric properties, and tunable mechanism. XRD results and temperature–permittivity curves show that rhombohedral phase and tetragonal phase exist at room temperature for y = 0.10. While only cubic phase can be found at (Ba_0.91Ca_0.09)(Zr_yTi_1−y)O₃ ceramics as y increases from 0.15 to 0.25. Moreover, Curie temperature T_m gradually shifts to low temperature with increasing Zr⁴⁺ content. The Curie temperature of (Ba_0.91Ca_0.09)(Zr_0.2Ti_0.8)O₃ ceramic is closed to room temperature, which makes it have a high tunability (66.9%) and low dielectric loss (0.00251) at ~ 6.70 kV/cm due to the influence of polar nano-regions. The excellent tunable performance achieved at low electric field makes (Ba_0.91Ca_0.09)(Zr_0.20Ti_0.80)O₃ ceramics have a great application in dielectric varactors.