Microstructure and properties of Nd₂O₃-doped (Ca_0.4Sr_0.4Ba_0.2)La₄Ti₄O₁₅ microwave dielectric ceramics

To address the demand for microwave dielectric ceramics with medium dielectric constant, low sintering temperature, and stable phase structure in rapid microwave communication development, Nd₂O₃-doped (Ca_0.4Sr_0.4Ba_0.2)La₄Ti₄O₁₅ (CSBLT)ceramics were synthesized via conventional solid-state reaction and the effects of Nd³⁺ incorporation on sintering behavior, phase evolution, microstructure, and microwave dielectric properties were investigated. The results show that Nd₂O₃ addition reduced the optimal sintering temperature from 1550 °C to 1475 °C and suppressed La₂Ti₂O₇ secondary phase formation. At low doping contents (≤2 wt.%), Nd³⁺ substituted for La³⁺ via solid solution, maintaining a pure hexagonal perovskite structure. At doping contents exceeding 4 wt.%, it will induce La₂TiO₅ precipitation, accompanied by grain refinement from 3.4 μm to 2.2 μm and morphological transition from rod-like to equiaxed grains. The dielectric constant decreased from 45.6 to 42.3, while the (Formula presented) value showed a strong positive correlation with grain size. Finally, CSBLT ceramics doping with 0.5 wt.% Nd₂O₃ exhibits the optimal microwave dielectric properties of (Formula presented)  = 45.3, (Formula presented)  = 38650 GHz, and (Formula presented)  = −7 ppm/°C. It has potential applications in microwave passive components (e.g., resonators, filters, and antennas) for 5G communication and satellite navigation systems.