In this study, high entropy ceramics, specifically Ba_0.5-xZn_xSr_0.45Ca_0.05TiO₃ (BZSCT), were synthesized using a solid-state reaction process and sintered at temperatures ranging from 1150 °C to 1250 °C. The properties of these ceramics were found to be significantly affected by variations in the Zn content. Densification of the BZSCT ceramics was observed to occur at sintering temperatures exceeding 1225 °C. Notably, the crystalline phases and dielectric properties of these ceramics were strongly influenced by the Zn content. Three distinct secondary phases were identified in the BZSCT ceramics, including BaZn_2.03Ti_3.93O_10.89, Ba₂ZnTi₅O₁₃ and Zn₂TiO₄. The addition of Zn resulted in a shift of the Curie point to lower temperatures. Specifically, with Zn substitution (up to 15 at.%), a Curie point of -60 °C was observed in the BZSCT ceramics. These ceramics exhibited a high dielectric constant of 1035, a low dielectric loss of 0.017%, and an impressive Q value of 442 when sintered at 1225 °C. Moreover, when comparing the dielectric constants of BZSCT ceramics at 1 MHz and 1 GHz, it was noted that the permittivity was only slightly reduced by less than 30% at lower frequencies. In contrast, the permittivity of BST ceramics decreased significantly, by approximately 70%, at microwave frequencies. These findings highlight the unique properties and potential applications of BZSCT ceramics, particularly in microwave applications where they outperform traditional BST ceramics.

Keywords: Microwave dielectric properties, Ba_0.5-xZn_xSr_0.45Ca_0.05TiO₃, High Entropy Ceramics, Secondary phase.