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Phase composition, morphology, and microwave dielectric properties of (1−x) LiAl0.98(Zn0.5Si0.5)0.02O2 + x CaTiO3 (0.05 ≤ x ≤ 0.20) materials synthesized via the solid state reaction method were investigated. All these densified materials were obtained at a sintering temperature of 1150°C. All compositions showed a major LiAlO2 phase that was accompanied by a minor CaTiO3 phase. The εr value increased gradually from 10.88 to 11.60, whereas the Q × f value remarkably decreased from 33 251 GHz to 13 511 GHz. The τf value changes from −85 ppm/°C to 212 ppm/°C, thereby indicating that CaTiO3 could effectively adjust this value. HBO3‐doping was used to further decrease the sintering temperature to 900°C. The optimum value was obtained at 7 wt.% HBO3 doped with microwave dielectric properties of εr = 9.39, Q × f = 10 224 GHz, and τf = −7.8 ppm/°C. This material also exhibited chemical compatibility with silver, making it a candidate for low temperature co‐fired ceramics applications. [ABSTRACT FROM AUTHOR]

The current study investigated the dielectric and electrical properties of BaAl (2−2 x) (Zn 0.5 Ti 0.5) 2 x O 4 ceramics, with x = 0, 0.4%, 0.8%, 1.2% and 1.6%, via impedance spectroscopy. The co-doping of Zn and Ti improved the temperature stability over −100 °C–700 °C of ε r and lowered tan δ due to the electron-pinned defect-dipoles. Effects of oxygen partial pressure on the electrical, dielectric and ferroelectric properties of x = 1.6% ceramic were studied as well. The bulk conductivity of the N 2 –H 2 -sintered and O 2 -sintered samples was attributed to the e ' and h • , respectively. [ABSTRACT FROM AUTHOR]

Novel LiAl5−xZnxO8−0.5x microwave dielectric ceramics were synthesized through a solid‐state reaction route. Phase evolution of LiAl5−xZnxO8−0.5x was determined by XRD analysis. The XRD results indicated that the phase compositions had a P4332 space group when 0 ≤ x ≤ 0.2 and a spinel structure when 0.3 ≤ x ≤ 0.5. The dielectric constant (εr) of this series' solid solutions decreased with the increase in Zn doping content, which was in good agreement with the Clausius‐Mossotti relation. Oxygen vacancy and the decreased degree of order degraded the quality factor (Q × f) of the two structures. The deterioration in quality factor was further verified by impedance spectroscopy. The temperature coefficient of the resonant frequency (τf) decreased with the increase in x and was correlated with the unit cell volume. Finally, CaTiO3 was used as a compensation material to obtain a near‐zero τf of the LiAl5O8 ceramic. [ABSTRACT FROM AUTHOR]

The structure and dielectric properties of BaAl (2−2 x) (Zn 0.5 Ti 0.5) 2 x O 4 ceramics were investigated. Single-phase solid solutions in space group P6 3 (No. 173) were confirmed when 0% ≤ x ≤ 1.6%. [Zn 0.5 /Ti 0.5 ]3+ averagely occupied four symmetrically inequivalent Al sites, and Al1/(Zn,Ti)–O, Al2/(Zn,Ti)–O and Al3/(Zn,Ti)–O bond lengths increased with increased x. Two dielectric anomalous peaks existed, the first peak referred to second-order ferroelectric transition. Stability was significantly improved by moving the first dielectric abnormal peak from 123 °C to −22 °C due to the lower atomic shift amplitude Δz of B cations along the polar axis. The co-doping of Zn2+ and Ti4+ played a decisive role in realizing an ultrabroad temperature range (−100 °C–700 °C) of stability (−27 ppm/°C ≤ TCC ≤ +10 ppm/°C), which met the conditions of C0G or NP0 multilayer ceramic capacitors (±30 ppm/°C). Superior insulating properties were performed by high resistivity of > 1014 Ω cm. [ABSTRACT FROM AUTHOR]

This study systematically investigated the structural, dielectric, and ferroelectric properties of BaAl(2−2x)(Mg0.5Ti0.5)2xO4 ceramics in the 0 ≤ x ≤ 0.04 range. Single‐phase solid solutions in the P63 space group with hexagonal crystal symmetry were confirmed in the composition range of 0 ≤ x ≤ 0.03. The bond lengths of Al1/(Mg,Ti)–O, Al2/(Mg,Ti)–O, and Al3/(Mg,Ti)–O increased with the increase in x, as confirmed through the Rietveld refinement and evolutions of corresponding modes in Raman spectra. The temperature stability of dielectric properties improved at a composition around x = 0.03, and the dielectric constant εr ascended with the increase in x. Ultrabroad temperature stability (−100°C to 700°C) was obtained, and an optimal combination (εr = 18.5, tan δ < 10−3, −22 ppm/°C ≤ TCC ≤ +20 ppm/°C, resistivity ~4.5 × 1014 Ω·cm) was achieved for the x = 0.03 ceramic sintered at 1260°C in air for 6 hours. The increase in stability was ascribed to the variations in axial bonds, and lattice distortions were determined through high‐resolution transmission electron microscopy. The x = 0.03 ceramic could be a promising candidate for C0G or NP0 multilayer ceramic capacitors because of its low loss, high reliability, superior insulating properties and comparatively low‐cost raw materials. [ABSTRACT FROM AUTHOR]

Low‐permittivity ZnAl2‐x(Zn0.5Ti0.5)xO4 ceramics were synthesized via conventional solid‐state reaction method. A pure ZnAl2O4 solid‐state solution with an Fd‐3m space group was achieved at x ≤ 0.1. Results showed that partial substitution of [Zn0.5Ti0.5]3+ for Al3+ effectively lowered the sintering temperature of the ZnAl2O4 ceramics and remarkably increased the quality factor (Q × f) values. Optimum microwave dielectric properties (εr = 9.1, Q × f = 115,800 GHz and τf = −78 ppm/°C) were obtained in the sample with x = 0.1 sintered at 1400°C in oxygen atmosphere for 10 h. The temperature used for the sample was approximately 250°C lower than the sintering temperature of conventional ZnAl2O4 ceramics. [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]

Ba 2 ZnSi 2 O 7 ceramic was prepared by conventional solid-state method and sintering under four different atmospheres (air, O 2 , N 2 , and N 2 –1 vol% H 2). The Ba 2 ZnSi 2 O 7 ceramic exhibited a single phase under air, O 2 , and, N 2 , whereas two phases (including BaSiO 3 impurity) were observed under the N 2 –1 vol% H 2 atmosphere due to Zn2+ evaporation. Dielectric loss was proportional to oxygen partial pressure due to the conduction mechanism of dominant holes. The Ba 2 ZnSi 2 O 7 ceramic exhibited good microwave dielectric properties (ε r = 8.3, Q × f = 27200 GHz, τ f = −41.5 ppm/°C) under the N 2 –1 vol% H 2 atmosphere, making it a novel candidate with good anti-reductive characteristics for base metal electrode–multilayer ceramic capacitor applications. [ABSTRACT FROM AUTHOR]

Ba 2 Zn (1+ x ) Si 2 O (7+ x ) ceramics were prepared using the conventional solid-state method at 1200 °C for 3 h in air. Apart from the previously reported Ba 2 Zn (1+ x ) Si 2 O (7+ x ) ( x = 0) with a monoclinic structure ( C 2/c ), the end-member compositions at x = −1 and 1 exhibit single-phase β -BaSiO 3 with an orthorhombic structure ( P 2 1 2 1 2 1 ) and BaZnSiO 4 with a hexagonal structure ( P 6 3 ), and possess a coexistence of weak ferroelectricity and low-permittivity microwave dielectric properties. A reduction in Zn 2+ content mainly decreases the intensity of the ε r anomaly peak at lower temperature and increases the ε r (or frequency) stability against temperature. The Zn 2+ -rich BaZnSiO 4 phase has a τ f value of −181 ppm/°C, whereas the τ f value of Zn 2+ -free BaSiO 3 phase decreases to −35.4 ppm/°C. The Zn 2+ deficiency in Ba 2 ZnSi 2 O 7 composition could inhibit the presence of BaZnSiO 4 phase and improve the τ f value, whereas excessive Zn 2+ cations prompt the formation of the BaZnSiO 4 phase to deteriorate significantly the τ f value. [ABSTRACT FROM AUTHOR]

Ba1+1/ M[Si2O5+1/ M] low-permittivity microwave dielectric ceramics are prepared using the conventional solid-state method. Pure phases are obtained in barium silicates with M = 1, 3, 4, 5, and ∞, except for M = 7, in which two phases, Ba5Si8O21 and BaSi2O5, are observed. As the complexity of the crystal structure described by the Shannon information per reduced unit cell increases, the τf value tends to change from a negative to a positive value, except for M = 5, which has the highest complexity. A single Ba5Si8O21 phase with εr anomaly peak at −180°C exhibits a rare positive τf value (+25 ppm/°C), which is a novel temperature compensator. [ABSTRACT FROM AUTHOR]