A series of high-k [(Na_0.5Bi_0.5)_xBi_1−x](W_xV_1−x)O₄ (abbreviated as NBWV(x value)) solid solution ceramics with a scheelite-like structure are synthesized by a modified solid-state reaction method at the temperature range of 680–760 ℃. A monoclinic (0 ≤ x < 0.09) to tetragonal scheelite (0.09 ≤ x ≤ 1.0) structural phase transition is confirmed by X-ray diffraction (XRD), Raman, and infrared (IR) analyses. The effect of structural deformation and order–disorder caused by Na⁺/Bi³⁺/W⁶⁺ complex substitution on microwave dielectric properties is investigated in detail. The compositional series possess a wide range of variable relative permittivity (ε_r = 24.8–80) and temperature coefficient of resonant frequency (TCF value, −271.9–188.9 ppm/℃). The maximum permittivity of 80 and a high Q×f value of ~10,000 GHz are obtained near the phase boundary at x = 0.09. Furthermore, the temperature-stable dielectric ceramics sintered at 680 ℃ with excellent microwave dielectric properties of ε_r = 80.7, Q×f = 9400 GHz (at 4.1 GHz), and TCF value = −3.8 ppm/℃ are designed by mixing the components of x = 0.07 and 0.08. In summary, similar sinterability and structural compatibility of scheelite-like solid solution systems make it potential for low-temperature co-fired ceramic (LTCC) applications.

Although many dielectric polymers exhibit high energy storage density (U_e) with enhanced dipolar polarization at room temperature, the substantially increased electric conduction loss at high applied electric fields and high temperatures remains a great challenge. Here, we report a strategy that high contents of medium-polar ester group and end-group (St) modification are introduced into a biodegradable polymer polylactic acid (PLA) to synergistically reduce the loss and enhance U_e and charge-discharge efficiency (η). The resultant St-modified PLA polymer (PLA-St) exhibits an U_e of 6.5 J/cm³ with an ultra-high η (95.4%), far outperforming the best reported dielectric polymers. It is worth noting that the modified molecular structures can generate deep trap centers and restrict the local dipole motions in the polymer, which are responsible for the reduction of conduction loss and improvements in high-temperature capacitive performance. In addition, the PLA-St polymer shows intrinsically excellent self-healing ability and cyclic stability surviving over 500 000 charge-discharge cycles. This work offers an efficient route to next-generation eco-friendly dielectric polymers with high energy density, low loss, and long-term stability.

Multi-band microwave absorption is becoming ubiquitous owing to the increasingly complex electromagnetic environment driven by the diversity of electronic devices. However, research on efficient electromagnetic absorbers applicable in both centimeter-wave and millimeter-wave bands to address the electromagnetic interference in 5G networks is highly challenging. In this study, Fe_x(Co_yNi_1-x)_100-x particles with two phases (face-centered cubic (FCC) and hexagonal close-packed (HCP)) were synthesized and were found to exhibit excellent electromagnetic wave absorption. HCP phase with high magnetocrystalline anisotropy was introduced into FCC phase Fe_x(Co_yNi_1-x)_100-x, resulting in natural resonances in multi-band frequency. Prominent microwave absorption properties in ultra-wide bandwidth ranging from 6.9 to 39.5 GHz were obtained. The maximum reflection loss (R_L) of the Fe₂₃(Co_0.5Ni_0.5)₇₇ composite film reached −50 dB. Such a remarkable absorption performance is attributed to the synergetic effects of the multiple natural resonances generated by the coexistence of HCP and FCC phases in Fe₂₃(Co_0.5Ni_0.5)₇₇. Overall, this work is promising for the future design of high-performance microwave absorbing materials in a wide bandwidth.

In this work, oxygen vacancy-regulated La_0.7Ca_0.3MnO_3-δ: Ag (LCMO: A) nanocomposite thin films on LaAlO₃ (001) substrates were investigated to obtain films with large temperature coefficient of resistance (TCR) values. LCMO: A nanocomposite thin films were synthesized using pulsed laser deposition, and oxygen pressures during film deposition and annealing steps were optimized. As oxygen pressures increased, lattice parameter increased from 70 Pa to 100 Pa, T_p increased monotonically from 168 K to 282 K, and average Mn⁴⁺ concentration in the film increased as indicated by X-ray photoemission spectroscopy data. Record high TCR value of ~37% K⁻¹ was achieved in LCMO: A nanocomposite thin film prepared with optimal oxygen pressures, making this film promising candidate for applications in bolometers.

In this work, the (1-x)CaWO₄-xNa₂WO₄ (x = 0.1, 0.2, denoted as 0.9CW-0.1NW and 0.8CW-0.2NW, respectively) ultralow-loss microwave dielectric ceramics were prepared via solid-state reaction method. Using low melting-point Na₂WO₄ as sintering aid to prepare CaWO₄Na₂WO₄ composite ceramics, the sintering temperature of CaWO₄ was successfully reduced while maintaining excellent microwave performance. The optimal microwave dielectric properties have been achieved at 900 °C for 0.9CW-0.1NW ceramic: ε_r = 9.0, Q × f = 105660 GHz, tanδ = 1.1 × 10⁻⁴ and τ_f = −35.4 ppm/°C at a frequency of 12.0 GHz. For the 0.8CW-0.2NW ceramic, the optimal microwave dielectric properties have been obtained at 740 °C, with ε_r = 8.5, Q × f = 97014 GHz, tanδ = 1.2 × 10⁻⁴ and τ_f = −37.4 ppm/°C at a frequency of 11.8 GHz. In summary, both composite ceramics exhibit low sintering temperatures, excellent dielectric properties and chemical compatibility with the Ag electrode. The findings of this study provide an effective approach to prepare novel composite ceramics as promising candidates for LTCC applications.