Investigation of crystal structure and chemical bonds characteristics on microwave properties of novel Ca-doped Sr1–Ca Tm2O4 (x=0.025–0.300) ceramics

Dense microwave dielectric ceramics of Sr 1– x Ca x Tm 2 O 4 ( x = 0.025–0.300) were fabricated via the conventional solid-state reaction method. Systematical investigations on the impact of Ca 2+ on their microstructures, sintering behaviors, and microwave dielectric properties were detailly conducted. The combined XRD data and subsequent refinement demonstrated that all samples exhibited structural conformity with SrTm 2 O 4 and belonged to Pnam space group. Calculations were executed to illustrate the evolution of performance-related chemical bonding parameters associated with Ca 2+ on the basis of the PVL theory. High density, lattice energy and narrow full width at half maximum of Raman modes contribute to a performance boost of around 14%. Excellent dielectric properties of Sr 0.95 Ca 0.05 Tm 2 O 4 , including relative permittivity of 15.97, quality factor of 47,142 GHz, and temperature coefficient of resonant frequency of −24.65 × 10 −6 °C −1 . Furthermore, Sr 0.95 Ca 0.05 Tm 2 O 4 ceramics were designed as rectangular dielectric resonator antennas with 388 MHz bandwidth at the center frequency of 6.525 GHz, along with high simulated radiation efficiency (≥90%) and realized gain (5.80–6.47 dBi), which suggests their considerable potential in 5G communication applications. • Addition of Ca 2+ was found to be beneficial in optimizing the sintering temperature. • P V–L bond theory was utilized to explore the chemical bond characteristics and structure-performance relationships. • Excellent properties were obtained in Sr 0.95 Ca 0.05 Tm 2 O 4 ceramic: ε r = 15.97, Q × f = 47,142 GHz and τ f = −24.65 × 10 −6 °C −1 . • A DRA based on Sr 0.95 Ca 0.05 Tm 2 O 4 ceramic was designed, confirming its application value in 5G communication.