Novel Mg7Ga2GeO12 microwave dielectric ceramics with ultralow-loss and low-permittivity for high-frequency packaging substrate

Study on the composite and properties of Y 2O 3–TiO 2 microwave dielectric ceramics

Dielectric ceramics with low sintering temperatures and superior performances are essential for electronic device applications. However, it is challenging to obtain glass‐free microwave dielectric ceramics with ultra‐low sintering temperatures. Herein, we introduce a low‐firing high‐performance scheelite ceramic, (CaSrNaBiLiY) 1/6 MoO 4 , using high‐entropy design to manipulate the grain boundary energy and reduce the intrinsic sintering temperature. A single phase high‐entropy ceramic with tetragonal scheelite structure is formed in (CaSrNaBiLiY) 1/6 MoO 4 , as demonstrated by X‐ray diffraction and transmission electron microscopy analyses. (CaSrNaBiLiY) 1/6 MoO 4 shows an ultra‐low sintering temperature of 580°C, good microwave dielectric properties with a permittivity of 21.1, a Q × f value of 10 200 GHz, and a temperature coefficient of resonant frequency value of 43.7 ppm/°C, and excellent chemical compatibility with Ag/Al electrode materials. The influences of high entropy on sintering temperatures and performances are discussed from the perspective of thermodynamic laws and lattice distortion effects. The grain boundary region with a thickness of ∼10 nm is rich in Ca element and the lattice distortion from multiple cations in A site increases the permittivity of high‐entropy ceramics. The microwave dielectric properties of (CaSrNaBiLiY) 1/6 MoO 4 are mainly derived from polarized optical phonons. This work provides a route for the development of glass‐free ceramics with reduced sintering temperatures using high‐entropy design.

Ultra-high-Q and wide temperature stable Ba(Mg1/3Tax)O3 microwave dielectric ceramic for 5G-oriented dielectric duplexer adhibition

Nearly half of the microwave dielectric materials include rare-earth elements based on a database presented by M. T. Sebastian. The presence of rare-earth elements helps to improve the microwave dielectric properties because the crystal structure is adjusted by the ionic radius of the rare-earth element. The microwave dielectrics are grouped by the crystal structure: (1) pseudotungstenbronze Ba6−3x R 8+2x Ti18O54 solid solutions, (2) homologous Ba n La4-Ti3+n O12+3n compounds (3) Y2BaCu2O5 green phases, (4) aeschynite LaYTiO6 and scheelite BaWO4 compounds, (5) perovskite-type ABO3 compounds, (6) garnet A 3 B 2′B 3″O12 compounds. The materials group (3)–(6) are presented. We discuss the groups (1)–(2) in this paper, and presented in “Microwave Dielectric Ceramics with Rare-earth (II)”.

In this study, a series of ([Formula: see text]x)Li2MoO4[Formula: see text]xBi0.4Ce0.6VO4 [x = 0.25, 0.35, 0.45, 0.55, ([Formula: see text]x)LM–xBCV] microwave dielectric ceramics, capable of being sintered at low temperatures, were synthesized using the solid-phase method. The temperature coefficient of resonance frequency in LM microwave dielectric ceramics was effectively modulated through the incorporation of BCV with tetragonal zirconia phases, resulting in the formation of composite ceramics. This approach led to the development of a low-permittivity ([Formula: see text]r ∼ 12.6) microwave dielectric ceramic material exhibiting a near-zero temperature coefficient (TCF ∼ +0.5 ppm/∘C). The composite, specifically 0.55LM–0.45BCV, achieved ultra-low temperature sintering below [Formula: see text]C and demonstrated excellent performance as low-temperature co-fired ceramic materials, with good co-firing compatibility with metallic silver. Furthermore, the volatilization of lithium and bismuth elements was effectively mitigated through the burying sintering process. Which resulted in a substantial enhancement of the [Formula: see text] (Q and f denote the quality factor and the resonant frequency, respectively) value for the 0.55LM–0.45BCV ceramics, achieving an increase of nearly threefold (Q × f [Formula: see text] [Formula: see text]GHz). To investigate the application potential of 0.55LM–0.45BCV ceramic, particularly in the context of low-orbit communication satellites, a circularly polarized patch antenna was designed utilizing 0.55LM–0.45BCV ceramic as the dielectric substrate material. The antenna demonstrated a high simulated radiation efficiency of 93.8% and a gain of 4.0[Formula: see text]dBi at a center frequency of 1.559[Formula: see text]GHz, indicating its promising applicability in the domain of orbital satellite communication.

Near‐zero temperature coefficient in Mg ²⁺ –Ti ⁴⁺ co‐doped Sm ₂ O ₃ –CaSmAlO ₄ microwave dielectric ceramics

This paper describes the potentials of zinc aluminate (ZnAl2O4) based microwave dielectric ceramics as patch antenna for GPS applications. Nowadays the GPS operating frequencies has been shifted from microwave technology to millimeter-wave technology. Various microwave dielectric ceramics (MDC) have been explored and widely used in telecommunication industries. Among the most interesting materials of that kind, zinc aluminate (ZnAl2O4) is recognized as one of the most promising non-metals and offers many advantages as GPS patch antenna. By modifying ZnAl2O4 compound with other materials, it is found to have high quality factor (Q>5,000), low dielectric constant (εr<20), and near zero temperature coefficient of resonant frequency (τf∼0). The studies also evidence the typical value of εr for GPS patch antenna and microwave substrate in the range of 4<εr<20 and 4<εr<10, respectively. The study also shows that the ZnAl2O4-based MDC can be successfully fabricated as microstrip patch antenna, which meets the requirements of GPS application.

Microstructure and microwave dielectric properties of Ba 5Nb 4O 15–BaWO 4 composite ceramics

Characterization and microwave dielectric properties of Mg2YVO6 ceramic

Temperature independent low firing [Ca0.25(Nd1-xBix)0.5]MoO4 (0.2 ≤ x ≤ 0.8) microwave dielectric ceramics

Microwave dielectric ceramics exhibiting a low dielectric constant (εr), high quality factor (Q × f), and thermal stability, specifically in an ultrawide temperature range (from -40 to +120 °C), have attracted much attention. In addition, the development of 5G communication has caused an urgent demand for electronic devices, such as dielectric resonant antennas. Hence, the feasibility of optimizing the dielectric properties of the SmNbO4 (SN) ceramics by substituting Bi3+ ions at the A site was studied. The permittivity principally hinges on the contribution of Sm/Bi-O to phonon absorption in the microwave range, while the reduced sintering temperature results in a smaller grain size and slightly lower Q × f value. The expanded and distorted crystal cell indicates that Bi3+ doping effectively regulates the temperature coefficient of resonant frequency (TCF) by adjusting the strains (causing the distorted monoclinic structure) of monoclinic fergusonite besides correlating with the permittivity. Moreover, a larger A-site radius facilitates the acquisition of near-zero TCF values. Notably, the (Sm0.875Bi0.125)NbO4 (SB0.125N) ceramic with εr ≈ 21.9, Q × f ≈ 38 300 GHz (at ∼8.0 GHz), and two different near-zero TCF values of -9.0 (from -40 to +60 °C) and -6.6 ppm/°C (from +60 to +120 °C), respectively, were obtained in the microwave band. A simultaneous increase in the phase transition temperature (Tc) and coefficients of thermal expansion (CTEs) by A-site substitution provides the possibility for promising thermal barrier coating (TBC) materials. Then, a cylindrical dielectric resonator antenna (CDRA) with a resonance at 4.86 GHz and bandwidth of 870 MHz was fabricated by the SB0.125N specimen. The exceptional performance shows that the SB0.125N material is a possible candidate for the sub-6 GHz antenna owing to the advantages of low loss and stable temperature.

Correlation among far-infrared reflection modes, crystal structures and dielectric properties of Ba(Zn1/3Nb2/3)O3–CaTiO3 ceramics

Effects of ion occupancy and polarizability on the crystal structure and microwave dielectric properties of CaEuCO4 (C[dbnd]Ga, Al) ceramics

LiB x Al 1

Preparation and characterization of the temperature-stable CaO-Li2O-Nd2O3-TiO2 microwave dielectric ceramics