Temperature-stable and low-loss microwave dielectrics based on [(Mg0.8Ni0.2)0.95Mn0.05]TiO3–CaTiO3 for 5G applications

This study presents a co-doped ilmenite-structured dielectric ceramic system, [(Mg1−xNix)0.95Mn0.05]TiO3 (MNMT), optimized for low-loss and thermally stable performance at reduced sintering temperatures. Ni2+ doping promotes lattice contraction and crystallinity enhancement, while Mn2+ improves densification and sintering behavior. The composition [(Mg0.8Ni0.2)0.95Mn0.05]TiO3, sintered at 1300 °C for 2 h, achieved εr ~ 17.4, Qf ~ 230,000 GHz, and τf ~ − 52 ppm/°C. Phase purity and structural homogeneity were confirmed via XRD, XPS, Raman spectroscopy, and SEM/EDS analyses. To address the strongly negative τf, CaTiO3 was incorporated into the MNMT matrix. The optimized (1 − x)MNMT–xCaTiO3 composition with x = 0.06 exhibited a balanced dielectric performance (εr ~ 20.88, Qf ~ 100,000 GHz) and complete τf compensation (~ 0 ppm/°C), sintered at 1325 °C for 2 h. The absence of secondary phases and the maintenance of dense microstructures confirmed the solid-state compatibility between MNMT and CaTiO3. This dual design strategy offers a viable route toward high-Q and thermally compensated dielectrics for microwave, 5G, and B5G system integration.