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Various defects have a profound impact on the dielectric properties and polarization mechanisms of (Nb,Ga) codoped TiO 2 crystals. However, the research conducted in this area remains limited. To address this, we grew (Nb,Ga) codoped TiO 2 crystals via the Verneuil method and investigated their dielectric properties under various atmospheric annealing conditions. Annealing in oxygen reduces the number of defects. In this case, the point defects associated with oxygen vacancies is unable to fully form the ideal complex defect clusters which can form effective pegging of free electrons. On the other hand, the defects are mainly in the form of simple defect clusters that causes hopping polarization. Annealing under mixed gas (Ar:H 2 = 95%:5%) increases the number of defects and contains more free carriers, which migrate to the interface between the sample and the electrode, leading to interfacial polarization. Both hopping polarization and interfacial polarization are slow polarization, resulting in an increase in dielectric loss and a decrease in frequency stability. Annealing in air or nitrogen atmospheres forms ideal defect dipole clusters, where the electron-pinned defect dipoles (EPDD) are predominantly polarized, resulting in superior dielectric properties. It has been clarified that EPDD as the main polarization form can yield better dielectric properties. By focusing on single crystals as the research subject, we effectively eliminate the influence of grain boundaries, enabling a more accurate assessment of the effects of various crystal defects on dielectric properties. This study holds substantial implications for the advancement of TiO 2 -based dielectric materials, offering valuable insights into their performance optimization. [ABSTRACT FROM AUTHOR]

High-performance dielectric materials are essential components of electronic devices. In this work, RE-doped SrTiO3 (RE = La, Nd, Yb) single crystals with excellent dielectric properties were prepared by the Verneuil method. For La-STO and Nd-STO, the RE ions are substituted for Sr2+ only, and the excellent dielectric properties are mainly caused by defect dipoles associated with oxygen vacancies including and defect dipole clusters. For Yb-STO, Yb3+ partially replaces Ti4+, forming an additional defect dipole , resulting in the best dielectric properties (ε′ = 3.6 × 104, tan δ = 0.0036 under 1 kHz). In addition, N2 atmosphere treatment promotes the production of oxygen vacancies and Ti3+ and the formation of more defect dipoles, thus further optimizing the dielectric properties of Yb-STO (ε′ = 4.9 × 104, tan δ = 0.004 under 1 kHz). This work suggests that the dielectric properties of RE-doped SrTiO3 materials are closely related to oxygen vacancies, and the simultaneous substitution of Sr2+ and Ti4+ should enable obtaining dielectric properties superior to those of the substitution of Sr2+ only. The present work provides a clearer understanding of the origin of SrTiO3 dielectric properties, which is of great significance to the development of SrTiO3-based dielectric materials. [ABSTRACT FROM AUTHOR]

A new high-entropy oxide, (Ge 0.2 Mn 0.2 Ti 0.2 Sn 0.2 Mo 0.2)O 2 with rutile structure, was successfully synthesized using solid-state reaction method. The phase structure of the ceramic samples prepared forming a range of binary to quinary phase with increasing entropy were investigated, and the effects of atmosphere-induction and high-entropy synergistic behavior on the dielectric performance were studied. As the type of the cations increases, the temperature required to form a single rutile structure gradually decreases, while the dielectric properties of the ceramics gradually improved. The dielectric constant of the (Ge 0.2 Mn 0.2 Ti 0.2 Sn 0.2 Mo 0.2)O 2 high-entropy oxide ceramics sintered in the nitrogen atmosphere at 1350°C is nearly 20 times higher of the ceramics sintered in the air. This significant enhancement can be attributed to the occurrence of two rutile structures and the generation of excessive oxygen vacancies as a result of high-entropy synergistic behavior under the nitrogen sintering atmosphere. [Display omitted] • A high-entropy oxide, (Ge 0.2 Mn 0.2 Ti 0.2 Sn 0.2 Mo 0.2)O 2 with rutile structure, was synthesized using solid-state reaction method. • Atmosphere induction has a significant impact on the dielectric properties of ceramic samples. • Compared to ceramics sintered in air, the dielectric properties of ceramics in nitrogen have been improved by nearly 20 times. [ABSTRACT FROM AUTHOR]

Novel high-entropy (La0.2Li0.2Ba0.2Sr0.2Ca0.2)Nb2O6-δ tungsten bronze ceramics, fabricated by conventional solid-state reaction, were first studied to reveal the effects of sintering temperatures on the crystal structure, microstructure and dielectric properties of these ceramics. The results show that all the prepared ceramics have tetragonal tungsten bronze structures after sintering at 1250–1350 °C. With increasing sintering temperature, high density up to 93% theoretical and uniform grain distribution are obtained. The dielectric properties are apparently affected by both frequency and temperature, and all ceramics exhibit quintessential relaxation peaks and obvious frequency dispersion phenomena. The optimal value of dielectric constant εr reaches as high as 1.1 × 106 at 100 Hz and 625 °C for the ceramic sintered at 1250 °C, which is almost 1290 times that of the (Ba1/3Sr1/3Ca1/3)Nb2O6 ceramics under the same conditions. Furthermore, the temperature stability of dielectric constant can also be improved through high-entropy effect. The obtained results demonstrate that it is feasible to design high-entropy ceramics to improve the dielectric properties of ANb2O6 ceramics. We have reason to believe that entropy engineering is a credible strategy for tailoring properties of ceramic systems. [ABSTRACT FROM AUTHOR]

The novel (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)2Ce2O7 high entropy ceramics were successfully fabricated by solid-state reaction method. The crystal structure, the particle morphology and dielectric properties were studied. The effect of sintering temperatures on the phase structure and dielectric properties of high entropy ceramics was investigated. The results showed that high entropy ceramics had a pure A2B2O7 phase of defective fluorite structure at 1300 °C. The dielectric measurements showed that the ceramics possessed decent dielectric stability at high frequency. The (La0.2Pr0.2Nd0.2Sm0.2Eu0.2)2Ce2O7 ceramic samples sintered at 1600 °C have large dielectric properties (the order of dielectric constant is 105–106) under the condition of high temperature and low frequency (about 320,000 at 642 °C, 100 Hz), which may be related to the high entropy effect. The insulation was demonstrated with the Leakage current density between 10–7 and 10–6 A/cm2, which showed the potential application value in microelectronics field. [ABSTRACT FROM AUTHOR]

In this study, La 2 (TiZrSnHfGe) 2 O 7 high entropy oxides were firstly prepared by solid state reaction method. The effects of different sintering temperatures on the structure, morphology and dielectric properties were studied. When the pre-calcination temperature is 1300 °C, the powder exhibits a single pyrochlore phase instead of defective fluorite phase. The existence of high entropy affects the changes in the crystal structure of A 2 B 2 O 7 type oxides, resulting in lattice distortion. The dielectric results showed that the ceramics have certain frequency dispersion, and the dielectric properties are affected by temperature and frequency. Due to the high entropy effect, the La 2 (TiZrSnHfGe) 2 O 7 ceramic exhibits good dielectric stability at both high and low frequencies. The formation of defect dipole clusters in the system results in the increase of dielectric constant. It is feasible to change the dielectric properties of ceramics by designing high entropy oxides, which showed the potential value in microelectronics field. [ABSTRACT FROM AUTHOR]

High-entropy ceramics (HECs), Ba(Ti1/6Sn1/6Zr1/6Hf1/6Nb1/6Ga1/6)O3, with perovskite structure were successfully synthesized through solid-state reaction method. HECs can be divided into three stages in the calcination process: from multiphase state to two-phase state and finally to single-phase perovskite structure. High entropy is the main driving force for the formation of perovskite HECs. The equilibrium phase of 1500 °C was transformed back to its multiphase state at low temperature, and vice versa on heating. The elements of the HECs are homogeneously distributed, and the relative density of the ceramic is 92.7%. The microstructures are fine, in which the average grain size is less than 1 μm. The dielectric constant εr and loss tangent tan δ exhibit slightly frequency dispersion. [ABSTRACT FROM AUTHOR]

(Nb 0.5 Ga 0.5) x Ti 1−x O 2 (x = 0.05%,0.2%,0.5%,1%,5%) single crystals were prepared by Verneuil method. Even if the doping amount is 0.05%, the dielectric permittivity (ε′) is obviously higher than that of pure rutile TiO 2 (260), reaching more than 104. As the doping amount x increase, the ε′ increases, and reaches the maximum value when x = 5%, but the dielectric loss increases correspondingly. The best dielectric performance (ε′=1.0 ×105, tanδ=0.034 under 1 kHz) is obtained when the doping amount is 0.5%. Even at 106 Hz, the dielectric loss is only 0.019, much lower than the reported ceramic samples. This may be due to the fact crystalline materials can effectively reduce defects such as grain boundary, second phase, porosity and segregation. The dielectric spectra, impedance analysis, XPS and DC bias results show that the colossal permittivity (CP) properties could be attributed to EPDD polarization. With the increase of doping concentration (>1%), the hopping polarization occurs, resulting in a slight increase in dielectric loss. These results indicate that TiO 2 crystal materials with lower dielectric loss are good candidates for dielectric materials. Taking TiO 2 crystal as the research object, we can have a clearer understanding of the origin of TiO 2 dielectric properties and the influence of doping ion content, which is of great significance to the development of TiO 2 -based dielectric materials. • (Nb 0.5 Ga 0.5) x Ti 1-x O 2 single crystals were prepared and their dielectric properties were studied for the first time. • The dielectric properties of doped crystal are improved and the best performance is obtained when the doping amount is 0.5%. • The dielectric loss is 0.019 at 106Hz , lower than the reported ceramics. And less than 0.1 from room temperature to 255℃. • Single crystal can eliminate the effects of defects and better understand the origin of dielectric properties. [ABSTRACT FROM AUTHOR]