Improved sinterability and microwave dielectric properties of [Zn_0.5Ti_0.5]³⁺‐doped ZnAl₂O₄ spinel solid solution

Abstract

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.

Phase Structures and Dielectric Properties of (n + 1)SrO − nCeO2 (n = 2) Microwave Ceramic Systems with TiO2 Addition

“…Additionally, Figure 3b demonstrates that all the vibration modes of the main peak (R 7 -R 12 ) are stable within the 287.17-386.21 cm −1 band range, and the Raman waveform of the main phase is still maintained within the Ti 4+ -ions' doping range, which can explain that the frequency band here is related to the stretching vibration of CeO 6 octahedra [32]. In summary, the analysis results of Raman spectroscopy correspond to those of the XRD analysis, which further verifies the credibility and correctness of the phase compositions and structures of these Under normal conditions, Raman spectroscopy can be used to characterize phase transitions and explore crystal structures, due to its sensitivity to structural anomalies [28,29]. Figure 3a shows the room-temperature Raman spectra of the xTiO2-(1 − x) (SrCeO3 + Sr2CeO4) (x = 0.0-0.4) ceramics sintered at their optimum temperatures for 4 h in the range of 50-900 cm −1 .…”

“…Based on this, it also indicates that the xTiO2-(1 − x) (SrCeO3 + Sr2CeO4) (x = 0.1-0.4) ceramic systems are a three-phase coexistence of the SrCeO3 phase, the Sr2CeO4 phase and the Sr2TiO4 phase. Under normal conditions, Raman spectroscopy can be used to characterize phase transitions and explore crystal structures, due to its sensitivity to structural anomalies [28,29]. Figure 3a shows the room-temperature Raman spectra of the xTiO 2 -(1 − x) (SrCeO 3 + Sr 2 CeO 4 ) (x = 0.0-0.4) ceramics sintered at their optimum temperatures for 4 h in the range of 50-900 cm −1 .…”

Ultra‐high Quality Factor of (Zn2/3Nb1/3)3+ Co‐substitution MgAl2O4 Microwave Dielectric Ceramics

“…[18] In strontium lanthanum aluminate (or SrLaAlO 4 ) and zinc aluminate (or ZnAl 2 O 4 ) ceramics, a high Qf value has also been achieved by substituting (Zn 0.5 Ti 0.5 ) 3þ for Al 3þ ions. [19][20][21] Moreover, (Cu 0.5 Ti 0.5 ) 3þ and (Mg 0.5 Ti 0.5 ) 3þ have been successfully introduced, improving the microwave dielectric properties of MgAl 2 O 4 ceramics. [22,23] These studies demonstrate that cosubstitution is an effective approach for enhancing the properties of MgAl 2 O 4 .…”

Solid-State-Activated Sintering of ZnAl2O4 Ceramics Containing Cu3Nb2O8 with Superior Dielectric and Thermal Properties

“…Furthermore, we also focused on ZnAl 2 O 4 (gahnite) as a base material; this aluminum-based oxide has good dielectric properties and is potentially more thermally conductive than alumina [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. According to Surendran et al, a sample produced by firing a 0.83ZnAl 2 O 4 –0.17TiO 2 (molar ratio) composition at 1440 °C exhibited a thermal conductivity of 59 W·m −1 ·K −1 [ 11 ].…”

“…Low-temperature sintering involving the addition of glass to ZnAl 2 O 4 [ 14 ] has been studied. The use of crystalline additives other than glass has also been studied a few times [ 16 ]; however, densely sintered ZnAl 2 O 4 has not been achieved below 1100 °C yet. Therefore, we aimed to develop a sintering additive that, when added in small amounts, enables ZnAl 2 O 4 to be densely sintered below 1000 °C (a low temperature).…”