Adjustable temperature coefficient of resonant frequency of low-permittivity CaY2-xMxGe3O10 (M = Sm, Yb) microwave dielectric ceramics

In this study, CaY 2- x M x Ge 3 O 10 ( M = Sm, Yb) ceramics with a P 2 1 /c space group were synthesised. Sm 3+ can fully substitute Y 3+ , whereas the solid solubility limit of Yb 3+ lies between 0.4 and 0.5. The corrected dielectric constant ( ε r-corr ) follows the trend of ε r-cal predicted based on the P-V-L theory, but is different with α D T / V m in CaY 2- x Sm x Ge 3 O 10 (1.2 ≤ x ≤ 2), where significant reductions in distortion of [YO 7 ] (Ave( δ Y − O )). The Q×f values, varying from 43,360±220   GHz to 113,620±680   GHz, are primarily governed by U t , P.F . , and E a . The τ f , varying from −9.6±0.1 ppm/°C to −217.6±2.0 ppm/°C, is influenced by both Ave( δ Y − O ) and fractional contribution of Ge−O bonds to overall susceptibility ( χ (Ge−O)/ χ ). Notably, CaY 1.6 Yb 0.4 Ge 3 O 10 ceramics exhibit a near-zero τ f (−9.6±0.1 ppm/°C) with ε r = 10.36±0.01 and Q×f = 92,540±560   GHz. CaY 1.7 Yb 0.3 Ge 3 O 10 achieves high Q×f of 113,620±680   GHz. CaY 0.8 Sm 1.2 Ge 3 O 10 ceramic demonstrates ε r = 10.31±0.01, Q×f = 50,510 ± 250   GHz, and τ f = −217.6±2.0 ppm/°C.