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(1 − x)CaTiO3–xLa(Mg2/3Nb1/3)O3 (CT–LMN; x = 0–1.0) solid solutions were prepared by a solid‐state reaction method. A phase transition from a disordered orthorhombic (Pbnm) structure to a 1:1 ordered monoclinic (P21/n) structure was observed when x increased from 0.5 to 0.6. Some new parameters, such as ionic polarizability in a polyhedron and ionic packing fraction in a polyhedron, were defined to explain the structure–property relationships of CT–LMN ceramics based on the Rietveld refinement results. The measured dielectric constant (εr‐mea) decreased monotonically with B‐site ionic polarizability in the [BO6] octahedron (αDT(B)/V[B]$\alpha _{\rm{D}}^{\rm{T}}({\rm{B}})/{V_{[ {\rm{B}} ]}}$) when the x value increased from 0 to 1.0. The quality factor (Qf) was dominated by the packing fraction of B‐site cations in the [BO6] octahedron (PF[B]), and both presented an increasing trend. The temperature coefficient of resonant frequency (τf) decreased from +588.5 to −79.7 ppm/°C, and it was highly correlated to the tolerance factor (t), αDT(B)/αDT(B)V[B]V[B]${{\alpha _D^T({\rm{B}})} \mathord{/ {\vphantom {{\alpha _D^T({\rm{B}})} {{V_{[ {\rm{B}} ]}}}}} \kern-\nulldelimiterspace} {{V_{[ {\rm{B}} ]}}}}$ and PF[B]. The highest Qf value is obtained at x = 1.0 when sintered at 1600°C for 10 h with εr = 23.65 ± 0.2, Qf = 33517 ± 2000 GHz (@7.8 GHz), and τf = −79.7 ± 2.0 ppm/°C. Moreover, a near‐zero τf value was achieved at x = 0.4 with εr = 43.52 ± 0.2, Qf = 17239 ± 2000 GHz (@5.2 GHz), and τf = −10.2 ± 2.0 ppm/°C. [ABSTRACT FROM AUTHOR]

High‐gain, low‐weight, wide bandwidth, and miniaturized lens antennas with stable properties against temperature are intensely required in extreme environments such as aerospace field. However, high‐performance microwave dielectric ceramics with near‐zero thermal expansion and frequency shift with temperature are very rare; moreover, the requirement of 3D printing processes also restricts their developments. Ba0.4Sr0.6Zn2Si2O7 with negative coefficient of thermal expansion (CTE), which originates from the stretched [ZnO4] tetrahedral chain to the twisted one along b‐axis with temperature, and CaTiO3 with positive temperature coefficient of resonant frequency (τf) can effectively adjust both CTE and τf of Zn1.8SiO3.8 to near‐zero value in 0.95(0.9Zn1.8SiO3.8–0.1Ba0.4Sr0.6Zn2Si2O7)–0.05CaTiO3 ceramic. Then, a Ku‐band Luneburg lens integrative antenna fabricated by stereolithography 3D printing technology exhibits an average gain of 8.06 dBi at 10.45–11.39 GHz and 10.3 dBi at 12.27–13.45 GHz, which has potential applications in temperature‐stable satellite communication. [ABSTRACT FROM AUTHOR]

A gillespite‐structured MCuSi4O10 (M = Ba1‐xSrx, Sr1‐xCax) ceramics with tetrahedral structure (P4/ncc) were prepared by solid‐state reaction method. X‐ray diffraction and thermogravimetry with differential scanning calorimetry (TG‐DSC) were employed to study the phase synthesis process of BaCuSi4O10. Pure BaCuSi4O10 phase was obtained at 1075°C and decomposed into BaSiO3, BaCuSi2O6, and SiO2 when calcined at 1200°C. The relationships between the crystal structure and microwave dielectric properties of MCuSi4O10 ceramics were revealed based on the Rietveld refinement and P‐V‐L complex chemical bond theory. The dielectric constant (εr) decreased linearly with decreasing total bond susceptibility and ionic polarizability. Quality factor (Q × f) was closely dependent on bond strength and lattice energy. The temperature coefficient of resonant frequency (τf) was controlled by the stability of [CuO4]6− plane in MCuSi4O10. Optimum microwave dielectric properties were obtained for SrCuSi4O10 when sintered at 1100°C for 3 hours with a εr of 5.59, a Q × f value of 82 252 GHz, and a τf of −41.34 ppm/°C. Thus, SrCuSi4O10 is a good candidate for millimeter‐wave devices. [ABSTRACT FROM AUTHOR]

BaZnSi3O8 ceramic was prepared by the conventional solid‐state method and sintered at 1100 °C. XRD and synchrotron Rietveld refinement analyses revealed the BaZnSi3O8 ceramic presented a monoclinic structure with a space group of P21/a (No.14), which is reported for the first time. The BaZnSi3O8 ceramic presented a weak ferroelectricity, which was confirmed by the P–E loop and the 90° nanoscale ferroelectric domain. Although ϵr–T displayed two ϵr abnormal peaks at 400 °C and 460 °C, the Curie temperature (Tc) was located at 460 °C according to the dielectric loss and Curie–Weiss law. Moreover, the BaZnSi3O8 ceramic exhibited optimized microwave dielectric properties with ϵr=6.55, Q×f=52400 GHz, and τf=−24.5 ppm/°C. Hence, the BaZnSi3O8 ceramic in the ternary BaO‐ZnO‐SiO2 system possessed both weak ferroelectricity and microwave dielectric properties. These results are expected to break the technical barrier of ferroelectric phase shifter applications in microwave and even millimeter‐wave frequency bands. [ABSTRACT FROM AUTHOR]

Resistive switching with a self-rectifying feature is one of the most effective solutions to overcome the crosstalk issue in a crossbar array. In this paper, a memory device based on Pt/TiOx/W structure with self-rectifying property is demonstrated for write-once-read-many-times (WORM) memory application. After programming, the devices exhibit excellent uniformity and keep in the low resistance state (LRS) permanently with a rectification ratio as high as 104 at ± 1 V. The self-rectifying resistive switching behavior can be attributed to the Ohmic contact at TiOx/W interface and the Schottky contact at Pt/TiOx interface. The results in this paper demonstrate the potential application of TiOx-based WORM memory device in crossbar arrays. [ABSTRACT FROM AUTHOR]

Low‐permittivity Ca1−xSrxSnSiO5 (0 ≤ x ≤ 0.45) microwave dielectric ceramics were prepared via traditional state‐reaction at 1400°C‐1450°C for 5 hours. Moreover the microwave dielectric properties of SnO2 ceramic were obtained for the first time. SnO2 ceramic was difficult to densify, and SnO2 ceramic (ρrel = 65.1%) that was sintered at 1525°C exhibited the optimal microwave dielectric properties of εr = 5.27, Q × f = 89 300 GHz (at 14.5 GHz), and τf = −26.7 ppm/°C. For Ca1−xSrxSnSiO5 (0 ≤ x ≤ 0.15) ceramics, Sr2+ could be dissolved in the Ca2+ site of Ca1−xSrxSnSiO5 to form a single phase, and the partial substitution of Ca2+ by Sr2+ could improve the microwave dielectric properties of CaSnSiO5 ceramic. Secondary phases (SnO2 and SrSiO3) appeared at 0.2 ≤ x ≤ 0.45 and could adjust the abnormally positive τf value of CaSnSiO5 ceramic. The highest Q × f value (60 100 GHz at 10.4 GHz) and optimal microwave dielectric properties (εr = 9.42, Q × f = 47 500 GHz at 12.4 GHz, and τf = −1.2 ppm/°C) of Ca1−xSrxSnSiO5 ceramics were obtained at x = 0.05 and 0.45, respectively. [ABSTRACT FROM AUTHOR]

A total of 14 fluoride composite ceramics were prepared through solid‐state method and their microwave dielectric properties were investigated. Among the fluoride composite ceramics, 0.36LiF–0.39MgF2–0.25SrF2 (LMS) had the lowest sintering temperature (600°C) and presented a dielectric constant (εr) of 6.24 ± 0.05, a quality factor (Q × f) of 33 274 ± 900 GHz, and a temperature coefficient resonant frequency (τf) of −86.74 ± 8 ppm/°C. As the LMS ceramic had a low melting point (646°C), it can be used as sintering aid for LTCC applications. The sintering temperature of BaCuSi2O6 decreased from 1050°C to 875°C with 2 wt% LMS doped and excellent microwave dielectric properties of εr = 8.16 ± 0.04, Q × f = 24 351 ± 300 GHz, and τf = −9.74 ± 1 ppm/°C were obtained. Moreover, BaCuSi2O6‐2 wt% LMS can be co‐fired with Ag powders, which makes it a potential new candidate for LTCC applications. [ABSTRACT FROM AUTHOR]

In this study, non-stoichiometric solid solution, Sr1–1.5(x+y)CexPryTiO3 abbreviated as (Sr, Ce, Pr)TiO3 (with 0.05 ≤ x ≤ 0.35 and y = 0.05, sintered in N2/H2 with 99% N2 and 1% H2) were prepared via a conventional solid-state method. By introducing (Ce0.25Pr0.05)3+/4+ on the A-site, the structure symmetry of the ceramic could be reduced, confirming cubic to tetragonal phase transition. Using Rietveld refinement and electron diffraction (TEM), the tetragonal phase was assigned to P4/mmm space group which posses a center of symmetry (centrosymmetric tetragonal unit cell). A small opening of hysteresis loop at higher Ce doping is assumed to be a caused by defect dipoles and conductivity. The dielectric anomalies were observed in all compositions, therefore, we assume that they are not related to structural phase transition but rather to some conductivity processes. [ABSTRACT FROM AUTHOR]

BaAl(2−2x)(Zn0.5Si0.5)2xO4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) solid solutions with weak ferroelectricity were prepared using a conventional solid-state reaction method. Zn atoms preferentially occupied the 6c-Wyckoff site of Al1 and the 2b-Wyckoff site of Al4, whereas Si atoms filled the 6c-Wyckoff site of Al2 and the 2b-Wyckoff site of Al3. As such, the cell volume shrank abnormally as the number of larger [Zn0.5Si0.5]3+ compared to Al3+ increased. There were two anomalous peaks in the dielectric constant. One peak at low temperature represented a second-order ferroelectric transition. Relaxor-like behaviour and a stable dielectric constant against temperature from −50 °C to 400 °C were observed at x = 0.4. This result was attributed to disorder in the 2b-Wyckoff site Al/(Zn0.5Si0.5) and distortion in the tetrahedron. [ABSTRACT FROM AUTHOR]