Solid-state Reaction Method Research Articles

Impact of Ca2+ and Zr4+ substitution on mechanical energy harvesting response of lead-free BaTiO3 piezoceramics with thermally stable storage density and efficiency

The Ba1-xCaxZryTi1-yO3 (BCZT; x = 0.18, y = 0.08; x = 0.15, y = 0.10; x = 0.12, y = 0.12; x = 0.09, y = 0.14; both x and y are in mol. %) piezoceramics were prepared by solid-state reaction method and investigated their energy storage and harvesting responses. The composition x = 0.15, y = 0.10 ( i.e. BCZT-2) reveals the morphotropic phase boundary (MPB) near room temperature with enhanced piezoelectric properties such as piezoelectric charge coefficient (d33) ∼ 380 pC/N, piezoelectric strain coefficient (d33*) ∼ 583.71 pm/V, piezoelectric voltage coefficient (g33) ∼ 14.09 ×10−3Vm/N, figure of merits (d33×g33) ∼ 5.35 ×10−12m2/N and the electromechanical coupling coefficient (kp) ∼ 0.291. The harvested peak-to-peak open circuit AC voltage is 30 V and the calculated current is in the range of 0.02–0.14 mA with varied load resistance and the maximum obtained power density is 13.38 μW/mm3 for BCZT-2 ceramics. The DC output signal of BCZT-2 ceramics successfully lit up the 'FCLNT' panel consisting of 53 red LEDs. At room temperature, BCZT ceramics have a recoverable energy storage density (Wrec) and storage efficiency (η) in the range between 506.46 and 257.49 mJ/cm3 and 50.53 – 64.93 % respectively. The composition x = 0.12, y = 0.12 (i.e. BCZT-3) revealed the highest energy storage efficiency (η) ∼ 64.93 % at room temperature. Nonetheless, the temperature-dependent (till its Curie temperature) maximum obtained Wrec of all BCZT ceramics is found in the range between 238.41 and 446.49 mJ/cm3 with an η of 66.98–79.67 %. Thus, compositionally tuned BCZT ceramics exhibit considerable piezoelectric properties, including energy storage and harvesting capabilities.

Study of phase composition, microstructure and hardness of multicomponent zirconia-based ceramics

The manufacture of products from refractory ceramics requires high temperatures due to the high activation energies of the sintering process of refractory oxides. Processing temperatures for ceramics made of ZrO2, Al2O3, MgO can be reduced if a flux or glass-forming component is selected. Furthermore, in multicomponent ceramics it is possible to create more favorable thermoresistive properties. This study examines the synthesis, structural, phase and mechanical properties of multicomponent porous ZrO2-WO3-Al2O3-MgO ceramics with varying weight concentrations of components. Experimental samples were obtained by standard solid state reaction method. The analysis of fabricated samples was carried out using X-ray phase analysis, scanning electron microscopy and the Vickers microhardness test. In this work, a new approach to increasing the microhardness of porous refractory ceramics is presented, in which WO3-based flux forms a matrix composed of glass-like formations that “attach” particles of ZrO2 and MgAl2O4 phases. The obtained ceramics demonstrates high microhardness values HV0.05 for porous materials ranging from 500 to 600. Studies have shown that the selected composition of multicomponent ceramics (x = 0.10–0.25) can be used as a refractory material up to temperatures of ∼1300 °C. The fabricated refractory ceramics potentially possess chemical stability and optimal microhardness properties, which makes these materials promising as a heat insulating lining in the metals, ceramics and glass manufacturing, as well as for components in the chemical industry.

Microwave dielectric properties of a temperature-stable and ultra-low sintering Li3AlMo3O12/Li0.5Bi0.5MoO4 composite ceramics for ULTCC application

Temperature-stable ULTCC composite (1-x)Li3AlMo3O12-xLi0.5Bi0.5MoO4 ceramics were prepared by solid-state reaction method. X-ray and EDS results showed that Li3AlMo3O12 phase and Li0.5Bi0.5MoO4 phase exist independently, and no other phase is generated. Due to the low sintering temperature of both two phases, the composite ceramics can obtain high density at 560 ℃. Microwave dielectric properties mainly depend on the ceramic Li0.5Bi0.5MoO4 content x, the addition of Li0.5Bi0.5MoO4 effectively increases the τf of Li3AlMo3O12 from −65.05 ppm/℃ to 4.96 ppm/℃, but caused the dielectric loss increase. When x=0.45 and sintered at 560 ℃, microwave dielectric properties of 0.55Li3AlMo3O12-0.45Li0.5Bi0.5MoO4 ceramics with close zero τf: εr = 15.32, Q×f = 13,158 GHz, τf = 4.96 ppm/℃.

Sm3+ activated Ba3LaNa(PO4)3F fluorophosphate phosphor: Synthesis, characterization and their photoluminescence investigation for warm WLEDs

In this present research report, the series of Ba3LaNa(PO4)3Fphosphor doped with Sm3+ was successfully synthesized by using a high-temperature solid-state reaction method. The phase purity was examined using X-ray diffraction (XRD), which confirmed a pure phase of prepared material after sintering the sample at 700 °C. Fourier transform infrared (FT-IR) spectra showed absorption bands corresponding to the stretching and vibrational modes of PO4 in phosphate. Scanning electron microscopy (SEM) images displayed the morphology of sample and agglomerated structure of micron-sized particles. Photoluminescence excitation (PLE) and emission spectra of the Ba3LaNa(PO4)3F: Sm3+ phosphors were studied. When excited with near-UV light, the phosphor showed three prominent peaks at 567, 604, and 643 nm. The emission spectra for different concentrations of Sm3+ ions were also measured to find the optimal dopant concentration. The highest intensity was observed at a 2.0 mol% concentration of Sm3+ ions at 604 nmwith concentration quenching occurring beyond this point. The CIE chromaticity coordinates for the different concentration phosphor were located in the orange-red region, indicating its characteristic light emission. So therefore, these results suggested that the synthesized reddish-orange light-emitting Ba3LaNa(PO4)3F: Sm3+prepared phosphor is promising for applications in white light-emitting diodes (WLEDs).

High-performance PSZT-PSMI-PSZS ceramics: Piezoelectric and ferroelectric insights for advanced applications

High-performance ferroelectric materials have garnered increased attention due to their exceptional dielectric, piezoelectric, and electrostrictive properties. A solid-state reaction method was used to prepare the perovskite Pb(1-x)Smx[(Zr0.52Ti0.48)0.9(Mo1/3In2/3)0.05(Zn1/3Sb2/3)0.05]O3 (where x = 0, 0.02, 0.04, 0.06, and 0.08) ceramics, abbreviated PSZT-PSMI-PSZS. Energy-dispersive X-ray spectroscopy (EDX) and Fourier-transform infrared (FT-IR) spectroscopy were employed to verify the elemental composition and molecular structure, respectively. The results showed good agreement between nominal and measured compositions, and indicated structural changes post-calcination, suggesting successful formation of the perovskite phase. Piezoelectric properties were evaluated, revealing the highest piezoelectric coefficient (d33 = 310 pC/N) at x = 0.02, attributed to optimal morphological features and the morphotropic phase boundary effect. This sample also demonstrated the highest electromechanical coupling factors (kp = 60 %, k31 = 35 %) and the largest impedance resonance frequency difference (Δf = 15.05 kHz). Ferroelectric testing indicated excellent ferroelectric characteristics, with the maximum remanent polarization (Pr = 17.71 μC/cm2) and saturation polarization (Ps = 22.75 μC/cm2) observed at x = 0.02, along with the lowest coercive field (Ec = 10.16 kV/cm). Additionally, this composition exhibited the highest unipolar strain (Smax = 0.17 %) and the inverse piezoelectric coefficient (d∗33 = 427.57 p.m./V). This comprehensive analysis emphasizes the potential of Sm-doped PZT-PMI-PZS ceramics for advanced piezoelectric and ferroelectric applications, particularly at a doping concentration of x = 0.02, where the materials exhibited excellent electrical and mechanical properties.

Effects of Pr substitution in Y1-xPrxBaCo3ZnO7+δ (0 ≤ x ≤ 0.5) cathodes for intermediate temperature solid oxide fuel cells

In this investigation, we successfully synthesized a series of Swedenborgite-type Y1-xPrxBaCo3ZnO7+δ (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5, abbreviated as YPxBCZ) oxides by a solid-state reaction method. The results show that YPxBCZ (x = 0.0, 0.1, 0.2, and 0.3) are single-phase structures, but YP0.4BCZ and YP0.5BCZ show interesting self-assembled composite phases. After long-term phase stability testing, YP0.3BCZ showed the best thermal stability. All samples show good chemical and thermal compatibility with La0.9Sr0.1Ga0.8Mg0.2O3-δ electrolyte. The thermal expansion coefficients in the temperature range from 30 °C to 1000 °C are equal to 9.8-13.1 × 10−6 K−1, close to that of the LSGM electrolyte. It is also found that Pr doping improves high temperature conductivity of YPxBCZ. The conductivity of YP0.3BCZ, YP0.4BCZ, and YP0.5BCZ reach 15.1, 18.5, and 22.5 S cm−1 at 800 °C. In addition, the area specific resistance (ASR) value decreases as the Pr content increases (0.038, 0.033, and 0.027 Ω cm2 at 800 °C for YP0.3BCZ, YP0.4BCZ, and YP0.5BCZ), improving the catalytic activity of the material. Another interesting finding was that the ASR of samples subjected to high temperature thermal decomposition was not adversely affected by the presence of decomposition products. The maximum power densities of YP0.3BCZ, YP0.4BCZ, and YP0.5BCZ in the single cells at 800 °C were 845, 930, and 1044 mW cm2, respectively. These results indicate that YP0.3BCZ, YP0.4BCZ, and YP0.5BCZ are promising cathode materials for intermediate-temperature solid oxide fuel cell.

Effect of Yb3+ on the thermophysical and mechanical properties of gadolinium zirconate ceramics: First-principles calculations and experimental study

Thermal barrier coating materials require high phase stability, low thermal conductivity, and a thermal expansion coefficient that matches the bonding layer. Cation doping is a highly efficient method for enhancing the thermophysical and mechanical characteristics of materials used in thermal barrier coatings. The thermophysical and mechanical properties, as well as the phase stability at high temperatures of ceramic materials doped with Yb3+ in gadolinium zirconate, are examined by utilizing first principles calculations and solid-state reaction methods. As the Yb3+ content increases, the grain average particle size of gadolinium zirconate ceramics first decreases and then increases. Given that a smaller grain size results in more grain boundaries, thereby reducing the thermal conductivity of the material, it can be inferred that Yb0.20 ((Gd0.8Yb0.2)2Zr2O7) with the smallest grain size exhibits lower thermal conductivity. As the Yb3+ content increases, both the calculated and experiment results suggest the Young’s modulus of gadolinium zirconate initially declines to its minimum value when the Yb3+ content is 0.5 and subsequently experiences a little increase. Furthermore, as the concentration of Yb3+ increases, the material initially experiences a drop in both hardness and fracture toughness, followed by a subsequent increase. Both the calculation and experimental results indicate that the thermal conductivity of gadolinium zirconate initially decreases and then increases. Among the different compositions, Gd1.5Yb0.5Zr2O7 demonstrates the minimum thermal conductivity, measuring 1.029 W/(m⸱K) according to the Clark model and 1.152 W/(m⸱K) according to the Cahill model. At a temperature of 1273 K, the experimental results demonstrated that (Gd0.8Yb0.2)2Zr2O7 has the lowest thermal conductivity of 1.415 W/(m·K). Furthermore, both the calculated and experimental thermal expansion coefficients of the material decrease first until the Yb3+ concentration is 0.5 and then increase slightly when the Yb3+ content increases. Moreover, gadolinium zirconate ceramics have demonstrated a consistent single-phase fluorite structure, excellent stability at high temperatures, and remarkable structural integrity during repeated heating and cooling cycles. The calculation results exhibit strong congruence with the experimental data. The objective of this work is to improve the thermophysical and mechanical properties of gadolinium zirconate ceramics for their application as materials for thermal barrier coatings.

Effect of Mn2+ substitution on the dielectric properties of NaMg(PO3)3 ceramics at microwave and terahertz frequencies

In this study, NaMg1-xMnx(PO3)3 (0.00 ≤ x ≤ 0.0625) ceramics with low dielectric constant were prepared via the solid-state reaction method. The effects of Mn2+ substitution on the microstructure and dielectric properties (at microwave and terahertz frequencies) of the NaMg(PO3)3 ceramics were studied by means of the Rietveld refinement, morphology, and ionic polarizability analysis. It is obtained that the NaMg0.0975Mn0.025(PO3)3 ceramic sintered at 880 °C for 4 h exhibited optimal dielectric properties at microwave frequencies, where εr = 4.585, Q × f = 48,313 GHz (@17.228 GHz), and τf = −40.83 ppm/°C. The Q × f and τf values were changed by 74.2 % and 27.8 %, as compared to the values of 27,728 GHz and −56.52 ppm/°C for the pure NaMg(PO3)3 ceramic, respectively. For terahertz frequencies (0.2–1.0 THz), the εr values were decreased to 3.79–3.98, and the tanδ values were between 0.0203 and 0.1152. All the experimental results indicate that this system exhibits great potentials both at microwave and terahertz frequencies.

Unveiling the potential of a novel inorganic perovskite for NTC thermistor and energy-storage applications

Inorganic perovskite-oriented materials are renowned for their multifunctional characteristics, making them candidates for various advanced applications. This study focuses on the synthesis and characterization of a novel inorganic perovskite material, (Ni0.5Sm0.5FeO3)0.5(BaTiO3)0.5, prepared via the cost-effective solid-state reaction method. Detailed structural and microstructural analyses were conducted to determine phase formation and grain size effects. Rietveld analysis was employed to identify the crystallographic phases, while field emission scanning electron microscopy (FE-SEM) provided insights into the sample’s morphology. FTIR and RAMAN spectroscopy were used to investigate the vibrational modes of the material. The dielectric properties and electrical characteristics were measured across a range of frequencies and temperatures using an impedance analyzer. The material’s potential for energy storage and NTC-type thermistor applications was evaluated through its temperature coefficient of resistance (TCR) and thermistor constant (β) analysis. Additionally, the ferromagnetic property was assessed through M−H hysteresis loop analysis, highlighting the material’s multifunctional capabilities.

Study of the Characteristics of Ba0.6Sr0.4Ti1-xMnxO3-Film Resistance Random Access Memory Devices.

In this study, Ba0.6Sr0.4Ti1-xMnxO3 ceramics were fabricated by a novel ball milling technique followed by spin-coating to produce thin-film resistive memories. Measurements were made using field emission scanning electron microscopes, atomic force microscopes, X-ray diffractometers, and precision power meters to observe, analyze, and calculate surface microstructures, roughness, crystalline phases, half-height widths, and memory characteristics. Firstly, the effect of different sintering methods with different substitution ratios of Mn4+ for Ti4+ was studied. The surface microstructural changes of the films prepared by the one-time sintering method were compared with those of the solid-state reaction method, and the effects of substituting a small amount of Ti4+ with Mn4+ on the physical properties were analyzed. Finally, the optimal parameters obtained in the first part of the experiment were used for the fabrication of the thin-film resistive memory devices. The voltage and current characteristics, continuous operation times, conduction mechanisms, activation energies, and hopping distances of two types of thin-film resistive memory devices, BST and BSTM, were measured and studied under different compliance currents.

Investigations on the mechanical and thermal properties of multicomponent dual-phase rare-earth zirconate ceramics

In this work, a series of multicomponent rare-earth zirconate (RE2Zr2O7, RE=La, Nd, Sm, Eu, Gd or Yb) ceramics were synthesized using solid-state reaction method. The phase stability and key factors affecting the thermal conductivity and mechanical performances were investigated. These materials possess pyrochlore-fluorite dual-phase structure and show excellent high-temperature phase stability. (La1/2Yb1/2)2Zr2O7 displays a lower amorphous-like thermal conductivity (1.39–1.67 Wm−1K−1, 25–1000 °C), while other specimens present a 1/T-like dependence at low temperatures. (La1/5Nd1/5Sm1/5Gd1/5Yb1/5)2Zr2O7 exhibit higher hardness (11.37 ± 0.35 GPa) and fracture toughness (2.10 ± 0.11 MPa·m1/2) in comparison with others. Size disorder shows stronger correlations with the thermal conductivity of multicomponent dual-phase RE2Zr2O7 ceramics, while the influence of configurational entropy is more significant for mechanical properties. A synergistic increase in configurational entropy and size disorder is an effective strategy to enhance the comprehensive performance of multicomponent dual-phase rare-earth zirconates.

A novel microwave dielectric ceramic CaB2O4 with low dielectric constant

A novel microwave dielectric ceramic CaB2O4 with low dielectric constant was synthesized by the solid-state reaction method. The impact of diverse Ca/B ratios on the phase composition, microstructure and dielectric properties of CaB2+xO4+3x/2 (x = 0–0.6) ceramics was investigated. The bond ionicity and the lattice energy of CaB2+xO4+3x/2 ceramics were calculated by the P-V-L theory. The appropriate excess of boron facilitated the densification of CaB2O4 ceramics, resulting in the stable crystal structure and enhanced dielectric properties. CaB2.3O4.45 ceramic sintered at 950 °C had excellent properties: εr = 6.03, Q×f = 37,962 GHz, and τf = −24.7 ppm/°C. The influence of TiO2 on the microwave dielectric properties of CaB2O4 was investigated, 87 wt% CaB2O4 - 13 wt% TiO2 ceramics sintered at 950 °C showed a zero τf value.

Structural, morphological, optical and down-conversion studies of NaLaMgTeO6:Dy3+ single phase phosphor for white light emitting applications and solar spectral converter for photovoltaic applications

Researches on rare earth activated phosphors in solid state lighting and enhancement in efficiency of solar cells pave attention to develop efficient phosphor materials. In the present work, Dy3+ doped NaLaMgTeO6 phosphors are synthesized using solid state reaction method. The structural studies using XRD analysis confirmed the successful formation of the compound. SEM analysis reveals that the particles are closely packed, which in turn exhibit intense luminescence intensity due to low scattering and high packing density. Elemental configuration were analyzed using EDS analysis. FTIR analysis revealed the vibrational bands of the host matrix. Optical energy bandgap was calculated using DRS spectra. The luminescence characteristics of the samples were investigated using excitation and emission spectra. Upon most intense 351 and 388 nm excitation, sharp yellow emission peak at 572 nm dominates blue emission at 478 nm, further reveals that Dy3+ ions occupy low symmetry site in the host lattice. The optimum concentration of Dy3+ in the present host is x = 0.04 mol and concentration quenching is due to dipole-quadrupole interaction of adjacent Dy3+ ions. The thermal quenching phenomenon is studied using temperature dependent photoluminescence analysis. The CIE chromaticity coordinates and CCT values conclude NaLaMgTeO6:Dy3+ phosphors are good candidate for cool near-white light emitting materials for outdoor illumination. The study on solar spectral response and down-conversion property of the synthesized phosphor demonstrate its applicability as solar spectral converters in solar cell applications.

The effect of lattice incorporation of Cu2+ in BaCe0.6Zr0.2-xY0.15Gd0.05CuxO3-δ proton conductor on its transport properties

In this paper, the introduction of Cu2+ into BaCe0.6Zr0.2-xY0.15Gd0.05CuxO3-δ (x = 0, 0.02, 0.04, 0.06; denoted as BCZYG, BCZYGCu0.02, BCZYGCu0.04 and BCZYGCu0.06, respectively)proton conductor materials. The effects of Cu doping strategy on the crystal structure, morphology and electrical properties of BCZYGCux proton conductor materials were systematically studied. The X-ray diffraction (XRD) results demonstrate that the synthesis of the BCZYGCux proton conductor material were successfully achieved through the solid-state reaction method. The scanning electron microscopy (SEM) analysis and relative density results indicate that an appropriate amount of Cu additions was conducive to lowering the sintering temperature and promoting the density of materials. A comprehensive analysis based on EIS and DRT was conducted to investigate the effects of temperature, testing atmosphere, and doping amount on the influence of conductivity on BCZYGCux proton conductor material. BCZYGCu0.02 has the largest total conductivity of 1.11×10-2 S·cm-1 at 700 ºC in the atmospheres of pO2=0.20 atm and pH2O=0.018 atm. The transference number of the BCZYGCux proton conductor material was calculated using a defect equilibrium model. The proton transference number of BCZYGCu0.02 is 0.97 at 500 °C. The BCZYGCu0.02 proton conductor has higher proton concentration and proton transference number in comparison to BCZYG. In conclusion, the Cu doping strategy has been demonstrated to be an effective method of improving the conductivity and proton transference number of BCZYGCux proton conductor materials. This provides a valuable insight into the optimisation of perovskite proton conductor performance.

Comparison of oxidation resistance of high-entropy (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C/SiC composites prepared by different methods at 1300–1600 °C

Dense monolithic (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C/SiC (HEC/SiC) composites were prepared via single-source-precursor (SSP) and solid-state reaction (SSR) method, respectively. The SSP-method nanocomposite features HEC nanoparticles uniformly dispersed within β-SiC, while the SSR-method composite is a microcomposite containing micro-sized HEC and β-SiC particles. The oxidation tests at 1300–1600 ºC show that the HEC/SiC nanocomposites exhibit much better oxidation resistance than that of the HEC/SiC microcomposites. Firstly, the generated metal-containing complex oxides ((Zr,Hf)6Ta2O17, Ti(Ta,Nb)2O7, and Ta-doped rutile TiO2) become more facile for sintering due to the nano-scaled HEC phase. Secondly, the cracks resulting from the oxidation of HEC nanoparticles are fewer and smaller, decreasing the number of channels for oxygen to pass through and channels need to be healed by SiO2. Finally, the homogeneous distribution of the HEC nanoparticles within β-SiC ensures the homogeneity of the complex oxide layer, significantly reducing the cracks caused by volume expansion and preventing the oxide layer from peeling off.

Origin of the ultrahigh field-induced strain in the Gd-doped 0.854Bi0.5Na0.5TiO3-0.12Bi0.5K0.5TiO3-0.026BaTiO3 ternary ceramic system

This study focused on analyzing the ferroelectric, piezoelectric, and dielectric properties of lead-free Bi0.487Na0.427K0.06Ba0.026TiO3 (0.854BNT-0.12BKT-0.026BT) ternary ceramic system by systematically doping 0.001, 0.01, 0.1, 0.5, and 1.0 mol% Gd2O3. The specific composition that was investigated is located at the tetragonal side of the rhombohedral-tetragonal morphotropic phase boundary (MPB) region. Undoped and Gd-doped BNT-BKT-BT ceramics were produced by the conventional solid-state reaction method. Ferroelectric, piezoelectric, and dielectric properties of ceramics were analyzed by carrying out electrical measurements from sintered samples. An ultrahigh field-induced unipolar strain of 0.52% at 65 kV cm−1, with a converse piezoelectric coefficient d33* of up to 795 pm V−1, was achieved with 0.5 mol% Gd doping. This was attributed to the Gd dopant disrupting the normal ferroelectric order and leading to the formation of a nonpolar relaxor phase. The field-induced transition from the nonpolar relaxor phase to the normal ferroelectric phase resulted in relatively large field-induced strain values in the 0.5 mol% Gd-doped ceramics. These results suggest that Gd-doped BNT-BKT-BT ceramics hold promise for digital actuator applications.

Impeding conduction by breaking the charge carrier hopping in charge-ordered perovskite BaBiO3 ([formula omitted]): Experimental and theoretical electronic structural correlations

BaBiO3 (BBO), a charge-ordered perovskite with mixed-valent states of Bi (Bi3+ and Bi5+), is known for its charge density wave (CDW) semiconducting and topological insulating properties. BBO has been extensively investigated for its superconducting, electrical, and photocatalytic properties. The present study aims to understand the alterations in the CDW and electronic properties of BaBi0.53+Bi0.55+O3 by valence-selective substitution of Bi3+ and Bi5+ with La3+ and Nb5+, respectively, in the solid solutions BaBi0.5−x3+LaxBi0.55+O3 and BaBi0.53+Bi0.5−y5+NbyO3 (x = y = 0.0, 0.1, 0.3, and 0.5). The samples synthesized via high-temperature solid-state reaction method were characterized by powder X-ray diffraction and various spectroscopic techniques (FT-IR, Laser Raman, EPR, XPS, and UPS). Impedance analysis revealed an upsurge in total impedance with the substitution of Bi3+/Bi5+ by La3+/Nb5+ indicating the blocking of electron/hole hopping by disruption of the charge ordering of redox pair Bi3+ and Bi5+. The valence-selective substitution of Bi3+/Bi5+ in BaBiO3 resulted in an alteration of the electronic structure and changes in the bandwidth of BaBi0.5−x3+LaxBi0.55+O3 and BaBi0.53+Bi0.5−y5+NbyO3 (x = y = 0.0, 0.1, 0.3, and 0.5) solid solutions, which were confirmed by both theoretical density of states (DOS) calculations and experimental ultraviolet photoelectron spectroscopic (UPS) studies.

Investigation of red-emitting CaMoO4: Eu3+ phosphor by partitioning of substitutional PO4 3- ions via solid-state reaction method.

To investigate the impact of PO4 3- anionic groups, the trivalent europium ion-doped calcium molybdate (CaMoO3-PO4:xEu3+, where x = 0.5, 1.0, 1.5, 2.0, and 2.5mol%) phosphors were synthesized using the solid-state reaction method. The detailed study of the phosphor materials was carried out by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), optical diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The XRD results indicate that the substitution of PO4 3- anion and Eu3+ dopant ion did not affect the crystal structures of the CaMoO4 phosphors. Ultraviolet-visible (UV-vis) absorption analysis revealed the change of absorption edge of both un-doped and Eu3+-doped CaMoO4-PO4 phosphors. Under the 394 nm UV-excitation, the recorded PL spectra showed an intense peak at 615 nm corresponding to the Eu3+: 5D0 → 7F2 transition. The results of the Commission Internationale de l'Eclairage (CIE) diagram reported that the color of the emissions lies in the red color zone and there is no change in the CIE coordinates of the overall emission for Eu3+-doped CaMoO4-PO4 as Eu concentration changes. Thus, these observations led to finding the best red components for white light-emitting diode applications.

A series of Ba12M0.5Zr0.5Nb9O36 (M=Ni, Mg, Co, and Zn) microwave dielectric ceramics with hexagonal perovskite structure

A series of hexagonal perovskite Ba12M0.5Zr0.5Nb9O36 (M = Ni, Mg, Co, Zn) ceramics were prepared by solid-state reaction method. XRD and Rietveld refinement results showed that all ceramic samples belong to the hexagonal perovskite structure with R-3m space group. With different B-site ion substitution, variation of permittivity (εr) can be ascribed to the average ion polarizability. Ceramics with highest relative density exhibit maximum quality factor (Q×f) values. Among all samples, the optimal microwave dielectric properties of εr = 35.2, Q×f = 57,985 GHz, and τf = 26.4 ppm/°C for Ba12Mg0.5Zr0.5Nb9O36 were obtained, which indicated that Ba12Mg0.5Zr0.5Nb9O36 ceramic is a candidate material for microwave communication applications.

Low permittivity germanate LaAlGe2O7 ceramics: Synthesis, sintering behavior, spectral characteristics and microwave dielectric properties

Novel low permittivity LaAlGe2O7 ceramics was prepared by a solid-state reaction method, and the relationship between microstructure and microwave properties was revealed. XRD and Rietveld refinement confirmed that the crystal structure of LaAlGe2O7 is monoclinic P21/c space group. Raman spectroscopy reflects the trend of internal structural order and phonon-damping behavior of LaAlGe2O7 ceramics. The ceramic sintered at 1250 °C exhibited the best surface morphology and optimum microwave dielectric properties of εr = 9.22, Q × f = 33417 GHz, τf = −71.68 ppm/°C. The lattice energy and packing fraction are used to explain the change of Q × f value. The relationship between phonon damping behavior and microwave dielectric properties was revealed. The temperature stability was studied by bond valence. The LaAlGe2O7 ceramics is a strong candidate for the substrate material of millimeter wave communication.