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In this study, La0.8Sr0.2MnO3 (LSM) was used as the ceramic electrode in a (Bi1.50Y0.50)0.98Zr0.04O3+δ (BYO)-based solid electrolyte oxygen generator (SEOG) and its performance was compared with that of a previously studied high-fire Ag electrode. Among La0.6Sr0.4Co0.2Fe0.8O3, LaNi0.6Fe0.4O3, Cu1.4Mn1.6O4, and LSM materials, only LSM materials did not trigger any chemical reaction or interdiffusion with BYO at temperatures up to 900 °C. Two cell designs, Cell A, with a Bi1.71Nb0.25Ba0.04O3+δ (BBNO) interlayer and high-fire Ag electrode, and Cell B, with an LSM-BYO composite electrode, were obtained in this study. The cells were sandwiched between two modular SUS 316 planar interconnects using a ZnO–SiO2–Al2O3 glass sealant to form the SEOG device. Although Cells A and B possessed similar ohmic resistance (Ro) values, the polarization resistance (Rp) values of Cell A were 3.6 times larger than those of Cell B. Furthermore, the stability study of the cells operated at 600 °C for 12 h revealed that Ro increased from 0.79 to 3.17 Ω cm2 and Rp from 3.12 to 12.58 Ω cm2 for the Cell A, while Ro increased from 0.76 to 0.77 Ω cm2 and Rp from 0.87 to 1.12 Ω cm2 for the Cell B. Therefore, minor variations in the Ro and Rp of Cell B indicate the excellent stability of the electrode. The degradation of Cell A was caused by the migration of Ag and formation of voids and cracks adjacent to the anode/electrolyte interface under the DC field. Furthermore, the Cell A experienced a decrease in faradaic efficiency for current densities greater than 0.20 A cm−2 owing to the partial decomposition of BYO at the cathode. In contrast, the Cell B generated an oxygen flux of 1.29 cm⋅min−1 at 600 °C. In addition, the faradaic efficiency of Cell B remained consistent for current densities up to 0.35 A cm−2. Therefore, the SEOG using LSM-BYO as the cell electrode exhibited excellent stability and electrochemical performance.

The dielectric and structural properties of the as-quenched melts of three CaO–B2O3–SiO2 compositions (denoted CBS-1, CBS-2, and CBS-3) were investigated to determine their suitability for use in millimeter-wave applications. The CBS-1 glass-ceramic exhibited the lowest coefficient of thermal expansion (CTE = 3.2 ppm/°C), lowest dielectric constant (er = 4.04) at 60 GHz, and highest dielectric loss (tan δ = 0.0029) at 60 GHz, which were attributed to the presence of quartz (SiO2) as the major phase. In contrast, as the major phase constituent of the CBS-2 and CBS-3 glass-ceramics was β-CaSiO3, they presented relatively high CTEs (6.6 and 5.9 ppm/°C, respectively), relatively high dielectric constants at 60 GHz (6.29 and 7.61, respectively), and relatively low dielectric losses at 60 GHz (0.0020 and 0.0012, respectively). The CBS-1 glass-ceramic exhibited the highest dielectric loss because of the presence of SiO2 as the major phase constituent as well as lattice scattering induced by the high glassy phase content. The thermal conductivities (κ) of the CBS-1, CBS-2, and CBS-3 glass-ceramics were determined to be 2.43, 1.06, and 0.82 W/mK, respectively. Structural analysis using Raman and Fourier transform infrared spectroscopy revealed an absence of nonbridging oxygen in the CBS-1 glass-ceramic, while the high CaO content (>40 mol%) of the CBS-2 and CBS-3 glass-ceramics triggered the formation of nonbridging oxygen in the tetrahedral silicate units. The increase in CaO content of the glass-ceramics increased the number of nonbridging oxygen atoms, thereby resulting in the relaxation of the structure. Consequently, the CBS-2 and CBS-3 glass-ceramics exhibited low thermal conductivity. All the prepared glass-ceramics presented high electrical resistivities of greater than 5 × 1011 Ω cm. The CBS-1 glass-ceramic displayed the highest breakdown strength of 15.20 kV/mm. Overall, the excellent microwave dielectric properties and thermal properties of the CBS glass-ceramics will facilitate the utilization of these materials in millimeter-wave applications.

In this study, BaTi0.65Zr0.35O3-2 mol% MgO ceramics with various amounts of Gd2O3 and SiO2 additives were prepared via a solid-state reaction method. The densification temperature of the BaTi0.65Zr0.35O3-2 mol%, MgO-2 mol%, and SiO2 ceramic was 1275 °C, with the addition of less than 2.0 mol% Gd2O3. The Gd3+ ions preferentially replaced the A-site ions. The densification temperature was reduced to 1225 °C, and the grain size of the ceramics was grown significantly up to 2.96 μm for 2 mol% Gd2O3, in addition to the formation of a trace amount of Ba2GdZrO5.5. There was a significant decline in the value of tanδ, and the electrical resistivity was increased by almost an order of magnitude due to the decrease in the V O • • concentration and the larger grain size. When the Gd2O3 content exceeded 2 mol%, the Gd3+ ions entered the B-site positions. For 5 mol% Gd2O3, the densification temperature is increased to over 1350 °C, the grain size reduced to 0.84 μm, and the value of tanδ is increased and the electrical resistivity is decreased as a result of the increasing V O • • concentration. The temperature coefficient of capacitance curves shows a nearly linear relationship between temperature and negative temperature coefficient and rotate counter-clockwise with an increase in Gd2O3 and SiO2 content. The BaTi0.65Zr0.35O3-2 mol% MgO-2 mol% SiO2 ceramics had a dielectric constant of 871 at room temperature, which decreased to 417 for 5 mol% Gd2O3. The dielectric constant of the BaTi0.65Zr0.35O3-2 mol% MgO ceramics, with and without the 2 mol% SiO2 additive, steadily declined by 10.2% at a bias field of 2.5 KV/mm. The magnitude of change in the dielectric constant has reduced significantly to 1.33% for the 5 mol% Gd2O3 additive.

The dielectric composition of 0.9BaTiO3-0.1(Bi0.5Na0.5)TiO3 with 4 mol% Ta2O5 sintered at 1230 °C revealed a dielectric constant (K) of 1179, tanδ values of 1.32% and 8.56%, and temperature coefficients of capacitance (TCCs) of 0.6% and − 14.05% at 25 °C and 200 °C, respectively, which meet the X9R specifications. In this study, various amounts of MnO additive were investigated for their ability to reduce the tanδ values of the compounds at 25 °C and 200 °C. Results indicated that the microstructure consists of fine equiaxed grains with a perovskite structure and second phases including plate-like Ba6Ti17O40, granular Ba3Ta3.2Ti5O21, and large granular Ba4Ti2O27 grains, depending on the MnO content. The MnO additive dramatically reduces tanδ values in the measured temperature range, even though it does not significantly change the microstructure for up to 4.5% addition. The 0.9BaTiO3-0.1(Bi0.5Na0.5)TiO3 with 4 mol% Ta2O5 and 0.01% MnO showed a K of 1107, tanδ values of 1.16% and 0.23% and TCCs of − 4.32% and − 13.81% at 25 °C and 200 °C, respectively. The dielectric properties of the formulations prepared in this study were highly repeatable, which confirmed their immense potential for use in X9R capacitors.

In this study, non-reducible high-temperature stable dielectrics based on 0.95BaTiO3-0.05Ba2LiTa5O15 compound with various dopants including Li2TiO3, MnCO3, CaCO3 and SiO2 were prepared through solid state reaction. The best composition obtained was 0.95BaTiO3-0.05Ba2LiTa5O15 with the addition of 5 mol% Li2TiO3, 1.5 mol% MnCO3, 2.0 mol% CaCO3 and 1.0 mol% SiO2. After being sintered at 1070 °C for 2 h in 3% H2-97%N2-3%H2 and heat-treated at 950 °C for 6 h in an atmosphere containing 100 ppm O2, the dielectric properties including temperature coefficient of capacitance (TCC): −3.6% at −55 °C and −9.2% at 200 °C, tanδ: 1.4% (−55 °C) and 11.2% (200 °C), electrical resistance: 1.2 × 1011 Ω-cm at 25 °C and 7.5 × 109 Ω-cm at 200 °C, and dielectric constant: 800 at 25 °C, were obtained, which meet the X9R requirements of EIA specifications.

In this study, seven glass sealants were explored for use in intermediate-temperature solid-oxide fuel cells (IT-SOFCs): one with boron oxide and an alkaline earth metal (AEM) oxide (GS01), one with boron oxide and free of AEM oxides (GS02), two with AEM oxides but free of boron oxide (GS03 and GS06), and three free of both boron oxide and AEM oxides (GS04, GS05, and GS07). The thermal stability, adhesion, and sealing properties of the glass systems were examined with respect to SUS 430 stainless steel (SUS430). All the glass sealants had electrical resistivities greater than 10 6 Ω-cm. The glass transition points ranged from 632 °C to 800 °C, while the glass softening points ranged from 708 °C to 852 °C. The GS01 and GS06 glasses, which contained AEM oxides, had lower glass crystal temperatures ( 11.6 ppm/°C), comparable to those of SUS430. The glasses without AEM oxides had lower CTEs but possessed good thermal stability at 700 °C. The glasses exhibited different levels of crystallization after being held at a sealing temperature of 850 °C for 1 h. With further soaking at 700 °C for 200 h, no new phases were formed. Scanning electron microscopy (SEM) was used to examine cross-sections of the interfaces of the glasses with SUS430 after heat treatment at 850 °C. The SEM results indicate that chromate was formed at the interfaces of the glasses containing AEM oxides (GS01, GS03, and GS06) and SUS430, while the glasses that were free of AEM oxides had smooth interfaces with SUS430 but cracks along the interfaces caused by the large differences in the CTEs. No significant inter-diffusion of species across any of the glass–SUS430 interfaces was observed. The leak rates of the glass seals were measured at 700 °C for 500 h after joining at 850 °C. The GS02 glass had the lowest leak rate of 0.017 sccm/cm. The glasses containing AEM oxides (GS01, GS03, and GS06) had high leak rates but good bond strength with SUS430. The GS06 glass had the highest bond strength, greater than 11 MPa.

In this study, ZnAl 2 O 4 (ZAO) films having a thickness of 20.1 nm, which serve as the resistive switching layer in random access memory (RRAM) devices based on a Pt/ZAO/Pt structure, were prepared using radio frequency magnetron sputtering. The as-deposited film appeared to be amorphous with distributed nano-crystalline ZnAl 2 O 4 particles, while the ZAO film annealed at 450 °C was composed of cubic ZnAl 2 O 4 spinel crystallites. The chemical formula of the former was (Zn 0.340 Al 0.66 )O 0.69 □ 0.64 while that of the latter was (Zn 0.91 Al 0.09 )Al 2 O 3.73 □ 0.27 , as calculated from energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) results, indicating that both these films consisted of oxygen vacancies. Pt/ZAO/Pt devices containing the as-deposited ZAO film exhibited excellent unipolar switching behavior marked with a resistance ratio larger than an order of magnitude, good endurance, and a long retention time. The conduction mechanisms for the low resistive state and high resistive state were dominated by the Ohmic conduction and trap-controlled space charge limited current mechanisms, respectively. The resistive switching behavior in the Pt/ZAO/Pt device was attributed to the formation and rupture of the conduction filaments formed by the oxygen vacancies.

In this study, Cu and Mo ions were doped in Ca 3 Co 4 O 9− δ to improve the electrical conductivity and electrochemical behavior of Ca 3 Co 4 O 9− δ ceramic and the performance of a solid oxide fuel cell (SOFC) single cell based on NiO-SDC/SDC/doped Ca 3 Co 4 O 9− δ -SDC were examined. Cu substitution in the monoclinic Ca 3 Co 4 O 9− δ ceramic effectively enhanced the densification, slightly increased the grain size, and triggered the formation of some Ca 3 Co 2 O 6 ; however, no second phase was found in porous Mo-doped Ca 3 Co 4 O 9− δ ceramics even when the sintering temperature reached 1050 °C. Substitution of Cu ions caused slight increase in the Co 3+ and Co 4+ contents and decrease in the Co 2+ content; however, doping with Mo ions showed the opposite trend. Doping the Ca 3 Co 4 O 9− δ ceramic with a small amount of Cu or Mo increased its electrical conductivity. The maximum electrical conductivity measured was 218.8 S cm −1 for the Ca 3 Co 3.9 Cu 0.1 O 9− δ ceramic at 800 °C. The Ca 3 Co 3.9 Cu 0.1 O 9− δ ceramic with a coefficient of thermal expansion coefficient of 12.1×10 −6 K −1 was chosen as the cathode to build SOFC single cells consisting of a 20 μm SDC electrolyte layer. Without optimizing the microstructure of the cathode or hermetically sealing the cell against the gas, a power density of 0.367 Wcm −2 at 750 °C was achieved, demonstrating that Cu-doped Ca 3 Co 4 O 9− δ can be used as a potential cathode material for IT-SOFCs.

The densification, microstructural evolution and microwave dielectric properties of (Ba 1− x Sr x )(Mg 0.5 W 0.5 )O 3 ceramics with x =0, 0.25, 0.5 and 0.75 are investigated in this study. The sintering temperature of the (Ba 1− x Sr x )(Mg 0.5 W 0.5 )O 3 is significantly reduced from 1575 °C to 1400 °C as the x value increases from 0 to 0.25 and 0.50; this result is accompanied by the formation of the (Ba 1− y Sr y )WO 4 phase and a small quantity of second phase surrounding the grains. The grain size of the (Ba 1− x Sr x )(Mg 0.5 W 0.5 )O 3 ceramics is increased by raising the Sr 2+ content, which significantly lowers the sintering temperature. The microstructure of the (Ba 0.75 Sr 0.25 )(Mg 0.5 W 0.5 )O 3 ceramic displays the smallest average grain size of approximately 0.8 μm, with a narrow grain size distribution. Without long annealing time, very high Q × f values are obtained for the (Ba 1− x Sr x )(Mg 0.5 W 0.5 )O 3 ceramics sintered at 1400–1575 °C for a duration of only 2 h. The (Ba 0.75 Sr 0.25 )(Mg 0.5 W 0.5 )O 3 ceramic sintered at 1400 °C results in the best microwave dielectric properties, including e r of 20.6, Q × f of 152,600 GHz and τ f of +24.0 ppm/°C.

In this study, various Cu-based spinel compounds, i.e. , CuFe 2 O 4 , CuMn 2 O 4 , CuAl 2 O 4 and CuLa 2 O 4 , were fabricated by a solid-state reaction method. Reduction behaviors and morphological changes of these materials have been characterized by H 2 temperature-programmed reduction (H 2 -TPR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Moreover, the catalytic properties for steam reforming of methanol (SRM) of these Cu-based spinel compounds were investigated. H 2 -TPR results indicated that the reducibility of Cu-based spinel compounds was strongly dependent on the B-site component while the CuFe 2 O 4 catalyst revealed the lowest reduction temperature (190 °C), followed respectively by CuAl 2 O 4 (267 °C), CuMn 2 O 4 (270 °C), and CuLa 2 O 4 (326 °C). The reduced CuAl 2 O 4 catalyst demonstrated the best performance in terms of catalytic activity. Based on the SEM and XRD results, pulverization of the CuAl 2 O 4 particles due to gas evolution and a high concentration of nanosized Cu particles (≈50.9 nm) precipitated on the surfaces of the Al 2 O 3 support were observed after reduction at 360 °C in H 2 . The BET surface area of the CuAl 2 O 4 catalyst escalated from 5.5 to 13.2 m 2 /g. Reduction of Cu-based spinel ferrites appear to be a potential synthesis route for preparing a catalyst with high catalytic activity and thermal stability. The catalytic performance of these copper-oxide composites was superior to those of conventional copper catalysts.

In this study, the effects of CaTiO 3 addition on the sintering characteristics and microwave dielectric properties of BiSbO 4 were investigated. Pure BiSbO 4 achieved a sintered density of 8.46 g/cm 3 at 1100 °C. The value of sintered density decreased with increasing CaTiO 3 , and sintering at a temperature higher than 1100 °C led to a large weight loss (>2 wt%) caused by the volatile nature of the compound. Samples either sintered above 1100 °C or with a CaTiO 3 content exceeding 3 wt% showed poor densification. SEM micrographs revealed microstructures with bimodal grain size distribution. The size of the smaller grains ranged from 0.5 to 1.2 μm and that of the larger grains between 3 and 7 μm. The microwave dielectric properties of the (1− x ) BiSbO 4− x CaTiO 3 ceramics are dependent both on the x value and on the sintering temperature. The 99.0 wt% BiSbO 4 –1.0 wt% CaTiO 3 ceramic sintered at 1100 °C reported overall microwave dielectric properties that can be summarized as e r ≈21.8, Q × f ≈61,150 GHz, and τ f ≈−40.1 ppm/°C, all superior to those of the BiSbO 4 ceramics sintered with other additives.

In this study, SrCo 1− y Sb y O 3− δ powders were prepared by a modified Pechini method. According to the study results, the cubic Pm3m phase of the SrCo 1− y Sb y O 3− δ ceramics was obtained as 10% of cobalt ions were substituted by antimony ions. Doping of Sb 3+ ions appeared both to stabilize the Pm3m phase of the SrCo 1− y Sb y O 3− δ ceramics and to enhance densification and retard grain growth. The coefficient of thermal expansion of the SrCo 1− x Sb x O 3− δ ceramics increased with the content of the antimony ions, ranging from 10.17 to 15.37 ppm/°C at temperatures lower than the inflection point (ranging from 450 °C to 550 °C) and from 22.16 to 29.29 ppm/°C at higher temperatures. For the SrCo 0.98 Sb 0.02 O 3− δ ceramic, electrical conductivity reached a maximum of 507 S/cm at 450 °C. The ohmic and polarization resistances of the single cell with the pure SrCo 0.98 Sb 0.02 O 3−δ cathode at 700 °C read respectively 0.298 Ω cm 2 and 0.560 Ω cm 2 . The single cell with the SrCo 0.98 Sb 0.02 O 3− δ -SDC composite cathode appeared to reduce the impedances with the R 0 and R P at 700 °C reading respectively 0.109 Ω cm 2 and 0.127 Ω cm 2 . Without microstructure optimization and measured at 700 °C, the single cells with the pure SrCo 0.98 Sb 0.02 O 3− δ cathode and the SrCo 0.98 Sb 0.02 O 3− δ -SDC composite cathode, demonstrated maximum power densities of 0.100 W/cm 2 and 0.487 W/cm 2 . Apparently, SrCo 1− y Sb y O 3− δ is a potential cathode for use in IT-SOFCs.

In this study, Ba(Zn 1/3 Ta 2/3 )O 3 -based complex perovskite compounds, including Ba(Zn 1/3 Ta 2/3 )O 3 , Ba(Zn 1/3 Ta 1/3 Nb 1/3 )O 3 , Ba(Zn 1/6 Co 1/6 Ta 2/9 Nb 2/9 Sb 2/9 )O 3 , and Ba 1/2 Sr 1/2 (Zn 1/6 Co 1/6 Ta 2/9 Nb 2/9 Sb 2/9 )O 3 , were prepared and characterized. There was no second phase formation shown in the XRD patterns. Though it has been suggested that substitutions of multiple ions over A-site or B-site of the Ba(Zn 1/3 Ta 2/3 )O 3 ceramics may not be beneficial to their microwave dielectric properties, the Ba(Zn 1/6 Co 1/6 Ta 2/9 Nb 2/9 Sb 2/9 )O 3 and Ba 1/2 Sr 1/2 (Zn 1/6 Co 1/6 Ta 2/9 Nb 2/9 Sb 2/9 )O 3 ceramics in this study were found to perform in a fairly acceptable manner. The Ba(Zn 1/6 Co 1/6 Ta 2/9 Nb 2/9 Sb 2/9 )O 3 ceramic (sintered at 1575 °C for 6 h) and the Ba 1/2 Sr 1/2 (Zn 1/6 Co 1/6 Ta 2/9 Nb 2/9 Sb 2/9 )O 3 ceramic (sintered at 1550 °C for 6 h) reported the following characteristics after annealing at 1400 °C for 10 h: 24.9 and 27.0 for dielectric constants ( ɛ r ), 83,000 and 32,100 GHz for quality factors ( Q × f ) values and −12.8 and −22.6 ppm/°C for temperature coefficients of resonance frequency ( τ f ).

Bi-layer electrolyte films of Zr0.84Y0.16O1.92 (YSZ)- 0.79Bi2O3-0.21Nb2O5 (BNO) were deposited by RF magnetron sputtering on NiO-SDC anode substrates. The stoichiometry of the BNO electrolyte film was found strongly dependent on the ratio of Ar and O2 during sputtering, and the BNO film deposited at a mixture of 31 sccm Ar and 7 sccm O2 appeared to be the closest to the target composition. When deposited at 300 °C and subsequently annealed at 700 °C, the BNO electrolyte emerged to be crack free and dense with some scattering closed pores. The XRD patterns of the film are indexed to the cubic Fm 3 ¯ m structure of Bi3NbO7. The as-deposited film was well-crystalline and consisted of fine grains and random orientation microstructures. For electrolyte thicknesses of approximately 4.0 μm YSZ and 1.5 μm BNO layers, the open circuit voltage (OCV) and the maximum power density of the single cell with Ag cathode read respectively 0.94 V and 10 mW/cm2 at 600 °C. These OCV values are lower than the expected theoretical value due to the high partial electronic conductivity.

Doped hexagonal BaTiO3 (h-BaTiO3) ceramics have recently been identified as potential candidates for use in microwave dielectric resonators. However, similar to other common microwave ceramics, doped h-BaTiO3 ceramics require a sintering temperature higher than 1400 °C. In this study, the effects of Bi2O3 and Li2CO3 on the densification, microstructural evolution and microwave properties of hexagonal 12R-Ba(Ti0.5Mn0.5)O3 ceramics were examined. Results indicate that Bi2O3 and Li2CO3 are able to effectively reduce the sintering temperature of 12R-Ba(Ti05Mn0.5)O3 ceramics through liquid phase sintering while retaining the hexagonal structure and the microwave dielectric properties. The best results were obtained for the 12R-Ba(Ti0.5Mn0.5)O3 with the additions of 5 wt% Bi2O3 sintered at 1200 °C (ɛr: 36.0, Qfr: 6779 GHz, and τf: 25.3 ppm/°C), and 5 wt% Li2CO3 sintered at 1200 °C (ɛr: 28.1, Qfr: 5304 GHz, and τf: 35.3 ppm/°C).

In this study, calcined TiTe 3 O 8 powder mixed with different amounts of SiO 2 was sintered at various temperatures. The effect of SiO 2 addition on the densification, microstructural evolution and dielectric properties of TiTe 3 O 8 was investigated. Results indicate that SiO 2 addition inhibited the grain growth of TiTe 3 O 8 and reduced the evaporation of TeO 2 . TiTe 3 O 8 ceramics with 1 wt% SiO 2 addition and sintered at 750 °C possesses the best dielectric properties: ɛ r value of 47.6, Q × f value of 48,800, and τ f value of +152 ppm/°C. Excess SiO 2 addition results in the poor densification and the existence of secondary phase (SiO 2 ) dissolved in a small amount of TeO 2 . They degrade the dielectric properties and trade off the benefit from the SiO 2 addition.

High density ZnO nanorod arrays were grown on Si substrates coated with ZnO seed layers via aqueous solution route. The ZnO seed layers were deposited on the substrate using DC reactive sputtering and RF magnetron sputtering. It was found that ZnO seed layer with (1 0 3) preferred orientation, prepared using DC reactive sputtering, did not facilitate the formation of ZnO nanorods in the solution grown process. Prior seeding of the surface by ZnO layer with (0 0 2) preferred orientation, deposited using RF magnetron sputtering, leads to nucleation sites on which ZnO nanorod arrays can grow in a highly aligned fashion. ZnO nanorods with well-defined hexagonal facets (0 0 2) were grown almost vertically over the entire substrate. The uniformity and alignment of the nanorod arrays are strongly related to the properties of underneath ZnO seed layers.

In this study, the characteristics of the polyimide/BaTiO 3 composite films with various amounts of BaTiO 3 were evaluated. Modifier 1-methoxy-2-propyl acetate was added during composite preparation to disperse the BaTiO 3 particles in polyimide matrix. Conversion of polyamic acid (PAA) to polyimide was not completed for the composite film with a high BaTiO 3 loading (90 wt%). Dielectric constant of the film increases from 3.53 to 46.50, at the sweep frequency of 10 kHz, as the BaTiO 3 content increases from 0 to 90 wt% (0–67.5 vol.%), which is mainly due to the relatively high dielectric constant of BaTiO 3 particles in the polyimide matrix. The dielectric losses at 10 kHz is ranging from 0.005 to 0.015, which is due to the switching of the domain wall. Water absorption decreases considerably with increasing BaTiO 3 content. With 10 wt% (2.5 vol.%) BaTiO 3 addition, the water absorption of the composite film reduces 45% from that of pure polyimide. Also, high loading of BaTiO 3 is not beneficial to reduce the water absorption of the composite film.

The effect of niobium doping on the densification and grain growth of nano-sized α-Al 2 O 3 powders during sintering has been investigated. The dopant concentration added ranged from 0.1 to 0.5 mol%. It was observed that addition of niobium oxide could improve the densification of the pure alumina with a lower sintering temperature, a shorter sintering time. The effect is strengthened by increasing the amount of dopant. It also demonstrated that niobium dopant significantly promotes the grain growth of alumina during sintering and the grain size of alumina increases with increasing the amount of dopant in the added range.

In order to relieve the narrow processing window and poor material compatibility in practical applications as well as understand the microwave dielectric properties, investigation on the formulations of CaO/B2O3/SiO2 glasses on their structure, thermal properties, and microwave properties were performed in this study. Six glasses with different molar ratios of CaO/B2O3/SiO2 (designed as CBS-3, CBS-5, CBS-7, CBS-8, CBS-9, and CBS-10) were prepared and pulverized. Results indicate that most softening points of glasses are ranging from 680 to 710 °C. They were sintered at different temperatures to reach maximum densification. Among various glass formulations, CBS-9 glass–ceramic containing the largest amount of SiO2 has the lowest CTE. The dielectric constants can be divided into two groups including around 4–5 and 7–8, and the dielectric losses (tan δ) are all below 0.005 in the frequency of ≈10 GHz. The dielectric constants and dielectric losses are generally frequency dependent. For CBS-9 glass–ceramic, the dielectric constant and dielectric loss at 4.7 and 18.6 GHz are 4.13 and 0.0018, and 4.20 and 0.0063, respectively.

Solid solution of Li 1−4 y − x Zr y +4 x Nb 1−3 x O 3 system is a new non-stoichiometric compound with orthorhombic perovskite structure. In this study, the effects of the calcination and the sintering temperatures on the microstructural evolution and microwave dielectric properties of Li 1−4 y − x Zr y +4 x Nb 1−3 x O 3 ceramics were performed. Dense Li 0.774 Zr 0.057 NbO 3 ceramics can be obtained at the sintering temperature of 1150 °C. Li 0.774 Zr 0.057 NbO 3 phase exists as the main phase with the existence of a minor LiNb 3 O 8 phase. Typical microwave dielectric properties for dense Li 0.774 Zr 0.057 NbO 3 ceramics are as followed: ɛ r ≈ 39, Q × f ≈ 4500, and τ f = −16.6 ppm/°C, measured at 6 GHz.

A synthesized magadiite has been organically modified by n -hexadecyl trimethyl-ammonium bromide (CTAB), and then grafted by γ-aminopropyltriethoxysilane (APTS). The formation of the CTAB-magadiite was confirmed by XRD, which the basal spacing increases from 1.54 to 2.46 mn. The formation of the organic derivatives of magadiite was confirmed by XRD, FTIR, and 29 Si CP-MAS NMR spectra. A silylating reagent of APTS was reacted to the CTAB exchanged magadiite. The copolymerization of the APTS modified magadiite presents a new layered silicate-organic compound. In this compound, a covalently bond formed between the interlayer spaces. It is dissimilar to the conventional clay-polymer systems in which the ionic interactions between silicates and organic modifiers are dominant.

In this study, Y2O3 and Nb2O5 doped titanium dioxide (TiO2) films on glass substrate were prepared using RF magnetron sputtering. The effects of dopants on the microstrucutral evolution and optical properties of TiO2 films were investigated. The as-deposited films are amorphous, irrespective of films containing Nb2O5 or Y2O3. After annealing at 400 °C and above in pure oxygen, anatase phase was obtained for pure TiO2 and Nb2O5 doped TiO2 films. Y2O3 dopant retards the crystallization to a higher temperature. After annealing, the transmittance of the TiO2 film is increased by Nb2O5 or Y2O3 addition. The higher transmittance of the doped samples can be correlated with their surface roughness.

The effects of glass additives and milling process on the microwave dielectric properties of (Zn1−x, Mgx) TiO3 (ZMT) ceramics were investigated. Three glasses including B2O3–SiO2–ZnO–Na2O (B–Si–Zn–Na), B2O3–SiO2–ZnO–K2O (B–Si–Zn–K) and B2O3–K2O–MnCO3 (B–K–Mn) were selected for this study. Host material (Zn0.6Mg0.4)TiO3 was selected to be sintered with glasses in the temperature range of 900–1200 °C. For (Zn0.6Mg0.4)TiO3 with 5 wt.% glass B–Si–Zn–K sintered at 1100 °C, the ϵr and Q × f values were 18 and 29,375, respectively. Taking advantage of satellite milling, the ZMT ceramics can be sintered at 950 °C with the density of 4.21 g/cm3, ϵr = 19, and Q × f = 18,957.

Preparation of dense and phase-pure Ba 2 Ti 9 O 20 is generally difficult using solid state reaction, since there are several thermodynamically stable compounds in the vicinity of the desired composition and a curvature of Ba 2 Ti 9 O 20 equilibrium phase boundary in the BaO–TiO 2 system at high temperatures. It was reported that a small amount of solid solution additives is essential for the formation of a pure Ba 2 Ti 9 O 20 phase, however, contradictory results were also addressed in the literature. In this study, TiO 2, MnO, and ZrO 2 , were used to investigate the effects of additives on the densification, microstructural evolution and phase stability of Ba 2 Ti 9 O 20 . With the addition of 2.8 wt.% TiO 2 and sintering at 1200 °C, ceramic yielded a pure Ba 2 Ti 9 O 20 phase. It indicates that Ba 2 Ti 9 O 20 is a nonstoichiometric compound, which can accommodate an excess amount of TiO 2 . With the addition of 4 wt.% ZrO 2 , phase pure Ba 2 Ti 9 O 20 was obtained in the sintering temperatures of 1200 °C and 1300 °C. Results also indicated that MnO addition could promote the formation of Ba 2 Ti 9 O 20 , compared with that of pure host material, though pure Ba 2 Ti 9 O 20 was not obtained. SEM microstructures are consistent with the observations in XRD patterns.

An ongoing research goal of thick film capacitors and multilayer capacitors is to lower the firing temperature of the dielectrics. This paper presents the results of using three simple glass systems including PbO–B2O3, PbO–SiO2, and Bi2O3–B2O3 as sintering aids for hydrothermal synthesized BaTiO3. Glasses with different ratios of the modifier/glass former were employed. Effects of adding these glass systems on the BaTiO3 ceramics sintered at 850°C were investigated through measuring and analyzing the density, grain size and dielectric property. It was found that BaTiO3 sintered with glasses composed of 90 mol% PbO–10 mol% SiO2 or 90 mol% PbO–10 mol% B2O3 to 60 mol% PbO–40% B2O3 are helpful to reduce the firing temperature for typical thick film and MLCC applications. They possess high dielectric constant (≈1650) due to their high densification characteristics with the grain size of ≈0.7 μm. In addition, glasses composed of 90 mol% Bi2O3–10 mol% B2O3 to 40 mol% Bi2O3–60 mol% B2O3 are beneficial for thin dielectric layer applications, on account of the high sintering density and a small grain size of ≈0.1 μm with an acceptable K value.

The electrical conductivity and thermal expansion coefficients of interfacial phases, PdPbO2, PdBi2O4, Pd(Pb), and Pd3Pb, have been studied. The interfacial reactions form low conductivity products, which result in discontinuity of the internal electrode. Besides, due to the volume change associated with the interfacial phase formation and wide variation in thermal expansions, physical defects may occur at the electrode–ceramic interfaces during processing.