Co-effects of Nb2O5 and stoichiometric deviations on the microwave dielectric properties of Y3Al5O12

B‐site internal‐strain regulation engineering of tungsten bronze structural dielectric ceramics

“…Besides, actual dielectric polarizability is also affected by the activity of electrons, which results in the little fluctuation of ε r . 32 Generally, as the vibrational energy decreases, the space for electron activity increases, which corresponds to more significant polarizability and higher dielectric constant, and the relationship between ε r and Raman shift can be analyzed by Equation ( 7) 33 :…”

“…Besides, actual dielectric polarizability is also affected by the activity of electrons, which results in the little fluctuation of ε r 32 . Generally, as the vibrational energy decreases, the space for electron activity increases, which corresponds to more significant polarizability and higher dielectric constant, and the relationship between ε r and Raman shift can be analyzed by Equation () 33 : $$$$\begin{equation}{\varepsilon }_r\ \left( {0,\xi ,k} \right) = \frac{{{{\Omega}}_p^2exp\left[ {\lambda \left( {E_p^0 - \xi } \right)} \right]}}{{\omega \left( {\xi ,k} \right)}}\ \end{equation}$$$$ω and $${{{\Omega}}}_p$$ are the phonon frequency and plasma frequency, respectively. The blue shift at 118 cm −1 and 143 cm −1 peak implies an increase in vibration energy and space for electron activity, which is attributed to the ions co‐substitution with different radius dispersion inevitably leading to different crystal structures, resulting in the different space for electron activity and slight fluctuations in ε r without absolute correspondence.…”

Ceramic compositions for 5G devices containing niobium: A survey

“…The ε r value was found dependent on the sample density and polarizability; the Qxf value was improved with increasing the grain size, and the τ f values were closely related to the bond valence of the cations in the AlO 6 octahedron. The optimal dielectric properties were found for Y‐deficient composition (Y 2.955 Al 5 Nb 0.045 O 12 ): ε r ∼10.37, Qxf ∼ 161 724 GHz, and τ f ∼ −33.8 ppm/°C 91 …”

Lattice evolution and microwave dielectric properties of La‐doped yttrium aluminum garnet ceramics

“…On the one hand, breakthroughs have been made in the microwave dielectric properties of novel garnet-based ceramics, for example, Sr 2 NaMg 2 V 3 O 12 8 with ε r = 11.7, Q × f of 37,950 GHz, and τ f value of −2.9 ppm/ • C; Ca 3 B 2 GeV 2 O 12 (B = Mg, Mn) 9 with ε r of 9.75 and 11.06, Q × f of 54,000 and 30,240 GHz, τ f of −61.2 and −66.4 ppm/ • C; A 3 Y 2 Ge 3 O 12 (A = Ca, Mg) 10 with ε r = 10.8 and 14.1, Q × f = 97,126 and 12,600 GHz, and τ f = −40.6 and 120.5 ppm/ • C; Sr 3 B 2 Ge 3 O 12 (B = Yb, Ho) 11 with ε r = 9.30 and 9.23, Q × f = 129,360 and 104,600 GHz, τ f = −42 and −26 ppm/ • C; Ca 3 MgBGe 3 O 12 (B = Zr, Sn) 12 ceramics with ε r = 10.80 and 9.68; Q × f = 79,600 and 83,400 GHz; and τ f = −66.8 and −57.9 ± 1 ppm/ • C. On the other hand, research studies on the modification of conventional yttrium aluminum garnets have also exhibited achievements. In 2016, Yu et al 13 reported the microwave dielectric properties of pure Y 3 Al 5 O 12 (YAG) transparent ceramics sintered at 1800 • C for 12 h: ε r = 10.8, Q × f = 213,400 GHz, and τ f = −30 ppm/ • C. In 2022, Wu et al 14 prepared Y 3 Mg 0.5 Al 4 Si 0.5 O 12 ceramics sintered at 1625 • C for 5 h by Mg 2+ and Si 4+ co-modifying and obtained excellent microwave dielectric properties with ε r = 10.56, Q × f = 67,571 GHz, and τ f = −35.23 ppm/ • C. However, due to the strict preparation process, the main research direction of ceramics in this system focuses on reducing the sintering temperature and improving the density of the ceramics, like adding sintering aid TEOS, 15 doping Nb 2 O 5 , 16 and adjusting the non-stoichiometry of YAG. 3 In fact, the ionic radius of Y 3+ ions is close to the ionic radii of rare-earth ions, providing the YAG ceramic with a wide range of ion substitution.…”

“…prepared Y 3 Mg 0.5 Al 4 Si 0.5 O 12 ceramics sintered at 1625°C for 5 h by Mg 2+ and Si 4+ co‐modifying and obtained excellent microwave dielectric properties with ε r = 10.56, Q × f = 67,571 GHz, and τ f = −35.23 ppm/°C. However, due to the strict preparation process, the main research direction of ceramics in this system focuses on reducing the sintering temperature and improving the density of the ceramics, like adding sintering aid TEOS, 15 doping Nb 2 O 5 , 16 and adjusting the non‐stoichiometry of YAG 3 …”