Ion Substitution Research Articles

Enhancing structural strength and microwave dielectric properties of the Ba4(Sm1-xCex)9.33Ti18O54 ceramics

Herein, microwave dielectric ceramics of the Ba4Sm9.33Ti18O54 ceramics are substituted at A sites by partially replacing Sm at A1 sites with Ce, and the effects of ionic substitution at A sites on ceramic crystal structure and microwave dielectric properties are investigated. The Ba4(Sm1-xCex)9.33Ti18O54 (BSCT) ceramics prepared through the solid phase method has a typical tungsten–bronze structure, and its lattice spacing increases gradually with the increase in Ce content x. This increase is reflected in the increase in the cell volume and growth of ceramic grains. However, the excess Ce after Ce content exceeds 0.25 leads to the growth of ceramic grains and increase in porosity between grains, which in turn increases the dielectric loss of the ceramic. Under optimal sintering conditions, the ceramic crystal has a maximum atomic packing density of x = 0.25, which corresponds to its most stable structural properties, and the highest Q × f value of 9013 GHz. Raman spectroscopy results indicate that in titanium oxygen octahedrons, an increase in Ce substitution can effectively weaken the bending and tensile vibration intensities of titanium oxygen bonds, further enhancing structural strength.

Sol-Gel Spin Coating Synthesis and Characterization of Cadmium Zinc Phosphate Thin Films: Structural, Optical, and Electrical Properties

This study successfully implemented the sol-gel and spin coating technique to grow cadmium zinc phosphate cadmium zinc phosphate (CZP) thin films on a glass substrate and p-Si wafer. Structural and morphological analyses were conducted via X-ray diffraction (XRD) and field-emission scanning electron microscopy (SEM). Additionally, the films’ linear and nonlinear optical properties, encompassing absorbance performance, energy gap, refractive index, dielectric, conductivity, and electronegativity, were systematically studied through UV–vis spectroscopy. XRD analysis uncovers the zinc ions substitution by cadmium ions in zinc phosphate’s unit cell, generating oxygen vacancies crucial for maintaining charge neutrality. SEM images then showcase the intricate and organized nano CZP framework. Shifting to optical studies, CZP film analysis spanning 190–2500 nm reveals an indirect energy band gap of 2.92 eV. Transitioning to electrical characteristics, the CZP/p-Si junction undergoes dark mode I-V-T analysis, elucidating the ideality factor, series resistance, and barrier height.

Anion substitution strategy for constructing abundant oxygen vacancies in perovskites enables efficient nitrate electroreduction

Perovskite oxides have emerged as promising candidates for electrocatalytic nitrate reduction (ERN) catalysts due to their unique electronic structures and tunable chemical compositions. In this work, we employed a fluorine ion substitution strategy to modulate the oxygen site of LaCoO3 (LCO), resulting in the construction of F-substituted LaCoO3 (LCOF0.5) catalyst for efficient ERN. The incorporation of fluorine ions leads to a weakening of the hybridization between the O 1 s orbital and Co 3d orbital of the catalyst, thereby inducing an increase in oxygen vacancies. The abundant oxygen vacancies can facilitate the electron transfer and surface adsorption energy of the ERN reaction intermediates. This leads to a reduction in the energy barriers for both the reduction of *HNO3 to *NO2 and the reduction of *HNO2 to *NO, thereby enhancing the performance of ERN. As excepted, LCOF0.5 exhibits a rapid reaction rate of k = 5.48 × 10−3 min−1, which is 1.70 times faster than that of pristine LCO, and its catalytic activity approaches that of the state-of-the-art electrocatalysts for ERN. Applying this strategy to LaFeO3 and LaMnO3 also yields similar results, demonstrating its general applicability. The F-anion substitution strategy offers new opportunities for significantly enhancing ERN performance.

Low-temperature sintering BCZT-Dy ceramics with low strain hysteresis for actuator application

Ba(Cu0.5W0.5)O3 (BCuW)-doped [(Ba0.85Ca0.15)1-xDyx](Zr0.1Ti0.9)O3 (BCZT-xDy, x = 0.001, 0.03) ceramics were prepared by conventional ceramic processing via low-temperature sintering technique. Rather pure perovskite structure and densified morphology with irregular nearly spherical-shape grains are achieved in all ceramics due to liquid-phase sintering. All BCuW-doped BCZT-xDy ceramics present apparent dielectric frequency dispersion and relaxor ferroelectric characteristic due to ion substitution and adding BCuW. The ceramics prepared at optimized sintering temperatures have rather large strain and small strain hysteresis, showing prospect application in piezoelectric high-precision actuators.

Exploring dielectric and electrical characteristics in Sr0.5Ba0.5SnxFe12-xO19/CoFe2O4 nanocomposites

This study examined the morphological, structural, electrical, and dielectric characteristics of hard-soft (H-S) Sr0.5Ba0.5SnxFe12-xO19/CoFe2O4 (x ≤ 0.10) ferrite nanocomposites (NCs), created using one-pot sol-gel combustion route. This study systematically investigated the electrical/dielectric features of H-S Sr0.5Ba0.5SnxFe12-xO19/CoFe2O4 NCs where x is within the range of 0.00 ≤ x ≤ 0.10. The examination realizes frequencies that reach 3.0 MHz, conducted within 20 °C–120 °C. A detailed analysis was performed to investigate various conduction mechanisms linked with dielectric constant, dissipation factor, AC/DC conductivity, loss of dielectric capacity, and real/imaginary modulus, which were explored across the entire range of Sn ion substitution ratios. Observations reveal that the conductivity variations adhere to power law dynamics concerning frequency, predominantly influenced by the Sn ion substitution ratios within the NCs. Furthermore, the frequency dependency of the dielectric coefficient across all NCs substantiates the common propagation of dielectric behavior, prominently contingent upon the substitution ratio of "x". Notably, the majority of dielectric parameters observed in H-S Sr0.5Ba0.5SnxFe12-xO19/CoFe2O4 (x ≤ 0.10) NCs are attributable to grain-to-grain boundaries, elucidated by conduction mechanisms similar to those observed in most compositional ferrites, explicable through Koop's model.

Crystal structure and spectral tuning of Eu2+/Eu3+ co-activated Na2Ba1-xSrxCa(PO4)2 phosphors with high thermal stability

The coupling of UV LED chips with phosphors to produce white or color-tunable light is still a challenge. In this work, we propose a simple rare earth occupation site engineering method to adjust the valence of doped Eu ions. Based on the Ba2+ substituted by Sr2+, new Eu2+/Eu3+ co-activated Na2Ba1-xSrxCa(PO4)2 (NB1-xSxCP) phosphors were designed and successfully synthesized. In NB1-xSxCP, the Ba2+/Sr2+ site is occupied by Eu2+, while the Ca2+ site is occupied by Eu3+. The coupled broad blue 448 nm and sharp red 619 nm luminescence under 321 nm excitation has demonstrated the coexistence of Eu2+ and Eu3+. This double emission phenomenon is studied in terms of the fluorescence lifetime as well as lattice distortion induced by the substitution ions. With the increased substitution of Sr, the luminescence of NB1-xSxCP:0.03Eu2+/3+ can be tuned from blue to red crossing the warm-white region. When x = 0.3, the chromaticity coordinates is located at (0.3779, 0.2495). The integrated intensity of Na2Ba0.7Sr0.3Ca(PO4)2:0.03Eu2+/3+ at 150℃ remains 90.9 % of that at room temperature, while the chromaticity shift (ΔE) can be calculated as 15 ×10−3. The Eu2+/Eu3+ co-activated NB1-xSxCP is a potential candidate for single-phase color-tunable phosphors used for light-tunable applications due to the combining contributions from both Eu3+ and Eu2+ ions.

Microstructural Study of the Coloring Variation of Chinese Sauce Glaze Replications

ABSTRACTSauce glazed wares of Yaozhou kilns are famous for their high gloss and distinctive glaze color palette varying from yellowish‐brown to reddish‐brown. In this work, sauce glazes were successfully replicated using the traditional technology of Yaozhou kilns. Micro‐Raman spectroscopy, combined with optical microscopy, scanning electron microscopy, x‐ray fluorescence, and reflective spectroscopy, was systematically applied to analyze the chemical composition, nature and distribution of crystals, and the coloration of the glazes. The results show that the yellowish‐brown glaze is mainly original from dendritic ε‐Fe2O3 crystals, whereas the reddish‐brown color is mainly derived from dendritic hematite crystals. Such dendritic structure could account for slightly color variations of the glaze surface observed in different angles, which also reported in Japanese Bizen ceramics. The principal component analysis (PCA) was further applied to study the Raman spectra of these iron oxides. The PCA results effectively indicates the structural disorders of these crystals introduced by ion substitutions. These substitutions could not only stabilize the crystals but also darken the crystals color. Besides, high Mg in the raw materials was found to benefit the growth of magnesioferrite crystals. The relative low level of Fe2O3, high level of SiO2, and CaO may relate to the formation of ε‐Fe2O3 crystals.

A prediction of high temperature magnetic coupling in transition metal phthalocyanines.

In spintronics, a perennial goal has been the generation of organic spin-bearing semiconductor materials with magnetic ordering stable at room temperature. To this end, the class of transition metal phthalocyanines has shown much promise in fulfilling this ambition. In particular, alpha-phase cobalt (II) phthalocyanine (α-CoPc) exhibits strong antiferromagnetic exchange interactions producing a long range order up to ∼100K. However, the underlying mechanism by which this magnetic interaction proceeds is not well understood. In this report, a simple mechanism has been proposed based on the Hubbard Hamiltonian, which elucidates the exchange coupling in α-CoPc. The mechanism provides stipulations for increasing the magnetic coupling, and this directs to a proposal that substitution of the central cobalt ion for rhodium will lead to a significant increase in coupling strength. The strength of this exchange interaction has been evaluated using broken symmetry hybrid exchange density functional theory and indicates that the novel rhodium (II) phthalocyanine system is indeed predicted to exhibit significantly stronger magnetic ordering. This study, therefore, identifies the coupling mechanism in α-CoPc as primarily attributable to kinetic exchange, explains its previously reported strong coupling relative to its first-row transition metal counterparts, and suggests that rhodium (II) phthalocyanine is likely to exhibit stable magnetic ordering at room temperature.

Systematic investigation of the influence of magnetic and non-magnetic ion substitutions in BiFeO3 under similar internal chemical pressure

Polycrystalline Bi1-xRxFeO3 (RHo and Y, x = 0.00, 0.05 and 0.10) compounds were prepared to perform a systematic investigation of the role of chemical nature and effect of internal chemical pressure on the structural, microstructural, magnetic, electric, ferroelectric and optical properties of the compounds. Structural analysis revealed that lattice distortions observed in Ho and Y-substituted compounds were not the same. The lattice parameters were larger in the case of the Y-substitution compared to the Ho-substituted counterpart. Scanning electron micrographs confirmed the formation of dense, well-connected grains exhibiting a reduction in size with increasing substitution. The magnetic properties of BiFeO3 were enhanced through the suppression of the spin structure with the substitution. The substitution of magnetic (Ho3+) ions led to an improvement in remanent magnetization and coercive field, whereas the substitution of non-magnetic (Y3+) ions resulted in enhanced maximum magnetization with negligible coercive field at room temperature. The ferroelectric measurements evidenced that both remanent polarization and coercive fields improved in substituted compounds, attributed to a decrease in charge carriers. Furthermore, the Y3+ ion substitution positively influenced ferroelectric properties by reducing leakage currents compared to the Ho3+ ion substitution. The optical absorption measurements indicated a decrease in the energy band gap of BiFeO3 with substitution, implying alterations in the material's optical characteristics. The ac conductivity studies demonstrated a discernible reduction in the conductivity of the substituted compounds. Specifically, Ho-substitution exhibited a more pronounced magnitude in the decline in conductivity relative to Y-substitution. This outcome signifies the potential efficacy of Ho-substitution in exerting control over the insulating characteristics of the compounds.

Unveiling the structural, optical, electrical, and ferromagnetic properties of Ca2+ doped mixed spinel ferrites for switching field high-frequency device applications

In this paper, the calcium-doped nickel-zinc nano-ferrites [Ni0.5Zn0.5CaxFe2-xO4; x = 0.00, 0.10, and 0.30] were prepared using the chemical co-precipitation synthesis route and studied for switching field high-frequency device applications. The structural analysis has been completed by analyzing X-ray diffraction (XRD) patterns. The Rietveld refined XRD patterns confirmed the formation of cubic spinel structure of Ca2+ substituted nickel-zinc ferrites. The detection of metal-oxygen bonds present at A and B lattice sites has been unveiled by Fourier transform infrared (FTIR) spectroscopy. The morphological studies obtained through FESEM (Field emission scanning electron microscopy) analysis showed a reduction in the particle size from 70 nm to 53 nm when the concentration of Ca2+ ions in Ni-Zn ferrites was increased. Energy dispersive spectra (EDS) confirmed the presence of elements present in the prepared composition. The structure of a cubic spinel-shaped unit cell has been verified from three active prominent Raman modes (A1g, A2g, and T2g). Diffuse-reflectance spectroscopy (DRS) exhibits the increment in the bandgap values (from 1.55 eV to 1.63 eV) which helps fabricate highly efficient photovoltaic devices. The ferroelectric measurements yielded a rise in polarization values from 1.461 μC/cm2 to 18.228 μC/cm2 for 10 % Ca2+ ion substitution. The tangent loss values declined from 24 to 3 in Ni-Zn ferrites upon substituting Ca2+ ions. The Vibrating sample Magnetometer (VSM) technique found the increment in the saturation magnetization (Ms) values from 34.724 emu/g to 54.662 emu/g on substituting up to 30 % Ca2+ ions in Ni-Zn ferrites. These obtained results support the material in switching field distribution for high-frequency applications. The results exhibited that the prepared samples can be applicable for switching devices, filters, and microwave absorption devices. The results revealed the maximum frequency between 12 and 18 GHz which is useful for Ku band absorption.

Ionic substitutions in the Cu3TeO6 structure type and magnetic properties of “medium entropy” Cu3/2Mn1/2Co1/2Fe1/2SbO6

Cubic antiferromagnet Cu3TeO6 demonstrates interesting magnetic properties. Aimed at modification of them, we tried multiple ionic substitutions in its structure. However, single-phase materials could only be prepared with large fraction of the Jahn-Teller ions (Cu2+ and Mn3+), although formally isostructural bixbyites R2O3 (R4O6) with R = Sc, In, Tl, Sm…Lu exist with no Jahn-Teller ions. Moreover, ions having highest octahedral crystal field stabilization energy (Ni2+ and Cr3+) were found least tolerable. This points to Cu3TeO6 as a separate structure type, distinct from classical bixbyites. We report crystal structure, magnetic and thermodynamic properties of a rare single-phase multicomponent preparation, Cu3/2Mn1/2Co1/2Fe1/2SbO6. The dc magnetic studies show that the formation of the ground spin-cluster state at T = 18 K is preceded by a broad anomaly at ∼122 K. Both specific heat and ac susceptibility data rule out the long-range magnetic ordering, in contrast to closely related Cu2MSbO6 (M = Mn or Fe).

Improved microwave dielectric properties of LaZn1/2Ti1/2O3 through Y3+ substitution

LaZn1/2Ti1/2O3 is a double perovskite with promising microwave dielectric properties for applications towards dielectric resonators and antennas. Its dielectric properties can be enhanced through the substitution of suitable ions in either A- or B-sites. In this paper, we report a significant improvement in the quality factor (Q) by substituting Y3+ in the La site with a marginal reduction in dielectric constant (εr). A single phase is confirmed in XRD indicating the formation of La1-xYxZn1/2Ti1/2O3 (0 ≤ x ≤ 0.25) solid solutions. The substitution results in an expansion of lattice along the b direction while there is a contraction in both a and c directions, leading to a reduction in unit cell volume. The dielectric constant, εr, is observed to reduce from 33.4 to 29.6 due to the polarizability of A-site atoms. The temperature coefficient of resonant frequency (τf) increases with an increase in x which does not appear to correlate with reducing tolerance factor (t). This non-conventional behaviour of τf in this perovskite based solid solutions brings bond valence of O site (VO) into picture. VO appears to show competing effect on τf. The non-monotonic behaviour is observed in Q×f with a maximum value of 41,400 GHz at x = 0.15 and a sharp decline for x > 0.15. This observation is correlated with variations in the A-site bond valence (VA) and a long-range ordering (LRO) of B-site ions. LRO is associated with Ag mode at 710 cm−1 in the Raman spectra. The low frequency (< 250 cm−1) Raman modes shift to a higher frequency with the increase in Y3+. Y3+ substitution also induces lattice distortion which is discussed in terms of variations in FWHM and relative intensity of the Raman modes.

Broadband SWIR emission through Cr3+-Ni2+ energy transfer in YAGG fluorescent ceramics for bioimaging applications

Short-wave infrared (SWIR) light in the 1000–1700 nm range has high penetration capability through biological tissues and is non-destructive, making it widely used in biomedical applications and near-infrared imaging. Currently, the development of SWIR light sources is urgently needed. This paper discusses the luminescent properties of the near-infrared emitting transition metal ions Cr3+ and Ni2+. By using the traditional high-temperature solid-state method, we successfully synthesized YAGG:3.5 %Cr3+-0.5 %Ni2+ (YAGG:Cr-Ni) garnet-based phosphor ceramic in one step. The phosphor ceramic emits ultra-broadband NIR-I (600–900 nm, FWHM=131 nm) and SWIR (1100–1700 nm, FWHM=377 nm) light when excited by a 450 nm commercial blue LED. Position analysis combined with density functional theory (DFT) simulation confirmed the effective substitution of luminescent center ions for the [Al/GaO6] sites. Spectral and lifetime analyses further verified the energy transfer process between Cr3+ and Ni2+ is dipole-quadrupole interaction. Additionally, this phosphor ceramic has a high thermal conductivity of 8.018 W·m⁻¹·K⁻¹ at room temperature. Finally, SWIR pc-LED devices were fabricated by packaging the phosphor ceramic with a 450 nm commercial blue LED, achieving skeletal and venous imaging of biological tissues up to 20 mm thick, providing a new approach for the development of SWIR devices.

SrCoO3-based perovskites with enhanced electrochemical performance through structural tailoring induced by B-site substitution

The progression of supercapacitor technology hinges on the discovery of high-performance electrode materials to enhance energy storage. SrCoO3-δ perovskite holds considerable promise potential as an anion intercalation electrode material. To elucidate the structural and electrochemical performance modulation rules of SrCoO3-based perovskites, this study synthesized SrCo0.875M0.125O3-δ (M = Ti, Ta, Nb, Fe) perovskites with different B-site ion substitutions. The structural tailoring induced by B-site substitution were thoroughly investigated alongside their corresponding electrochemical performance. Notably, SrCo0.875Ti0.125O3-δ exhibited a simple cubic structure, while the other samples displayed a tetragonal structure. Additionally, SrCo0.875Fe0.125O3-δ displayed numerous oxygen vacancies and significant distortion in the [CoO6] octahedron, which is attributed to the lower valence state of Fe. At a current density of 1 A g−1, the specific capacities of SrCo0.875M0.125O3-δ (M = Nb, Ti, Fe, Ta) perovskites were 984.43, 853.33, 503.53, and 452.00C/g, respectively. SrCo0.875Nb0.125O3-δ demonstrated the highest specific capacity and capacity retention rate across various current density, owing to its relatively stable structure with appropriate oxygen vacancies and multivalent state changes of Nb. In contrast, SrCo0.875Fe0.125O3-δ, with excessive oxygen vacancies and severe structural distortions, exhibited restricted electrochemical performance, particularly at higher current densities. Integrating structural and performance analysis, this work proposes an optimization strategy for the electrochemical performance of SrCoO3-δ-based perovskite electrode materials, emphasizing the importance of tailoring multivalent B-site elements to achieve a stable perovskite structure with appropriate oxygen vacancies.

Mixed-valence state in the dilute-impurity regime of La-substituted SmB6

Homogeneous mixed-valence (MV) behaviour is one of the most intriguing phenomena of f-electron systems. Despite extensive efforts, a fundamental aspect which remains unsettled is the experimental determination of the limiting cases for which MV emerges. Here we address this question for SmB6, a prototypical MV system characterized by two nearly-degenerate Sm2+ and Sm3+ configurations. By combining angle-resolved photoemission spectroscopy (ARPES) and x-ray absorption spectroscopy (XAS), we track the evolution of the mean Sm valence, vSm, in the SmxLa1−xB6 series. Upon substitution of Sm ions with trivalent La, we observe a linear decrease of valence fluctuations to an almost complete suppression at x = 0.2, with vSm ~ 2; surprisingly, by further reducing x, a re-entrant increase of vSm develops, approaching the value of vimp ~ 2.35 in the dilute-impurity limit. Such behaviour departs from a monotonic evolution of vSm across the whole series, as well as from the expectation of its convergence to an integer value for x → 0. Our ARPES and XAS results, complemented by a phenomenological model, demonstrate an unconventional evolution of the MV character in the SmxLa1−xB6 series, paving the way to further theoretical and experimental considerations on the concept of MV itself, and its influence on the macroscopic properties of rare-earth compounds in the dilute-to-intermediate impurity regime.

Impact of Co2+ substitution on structure and magnetic properties of M-type strontium ferrite with different Fe/Sr ratios

Abstract Ion substitution has significantly improved the performance of ferrite magnets, and cobalt remains a key area of research. Studies on the mechanism of Co2+ in strontium ferrite, especially SrFe2n–x Co x O19–δ (n = 6.1–5.4; x = 0.05–0.20) synthesized using the ceramic method, showed that Co2+ preferentially enters the lattice as the Fe/Sr ratio decreases. This results in a decrease in the lattice constants a and c due to oxygen vacancies and iron ion deficiency. The impact of Co substitution on morphology is minor compared to the effect of the Fe/Sr ratio. As the Fe/Sr ratio decreases and the Co content increases, the saturation magnetization decreases. The magnetic anisotropy field exhibits a nonlinear change, generally increasing with higher Fe/Sr ratios and Co content. These changes in the performance of permanent magnets are attributed to the absence of Fe3+ ions at the 12k + 2a and 2b sites and the substitution of Co2+ at the 2b site. This suggests that by adjusting the Fe/Sr ratio and appropriate Co substitution, the magnetic anisotropy field of M-type strontium ferrite can be effectively optimized.

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.

Theoretical Study of Co-Doping Effects with Different Ions on the Multiferroic Properties of BiFeO3 Nanoparticles.

Using a microscopic model and the Green's function theory, the size and co-doping effects on the multiferroic and optical (band gap) properties of BiFeO3 (BFO) nanoparticles are investigated. The magnetization increases, whereas the band gap energy decreases with decreasing nanoparticle size. The substitution with Co/Mn, Nd/Sm, Ce/Ni, and Cd/Ni is discussed and explained on a microscopic level. By the ion co-doping appear different strains due to the difference between the doping and host ionic radii, which leads to changes in the exchange interaction constants for tuning all properties. It is observed that by co-doping with Nd/Sm at the Bi site or with Co/Mn at the Fe site, the multiferroic properties are larger than those by doping with one ion. Moreover, by doping with Ni, the multiferroic properties are reduced. But by adding another ion (for example Ce or Cd), an increase in these properties is obtained. This shows the advantages of the co-doping, its flexibility, and its greater possibility of tuning the multiferroic properties compared to single ion substitution. The band gap energy decreases for all co-dopants. The polarization increases with increasing magnetic field. This is evidence of magnetoelectric coupling, which is enhanced by co-doping with Co/Mn. The observed theoretical results are in good qualitative agreement with the existing experimental data.

Surface active sites and interphase engineering into metal oxide hydrates enabled by ions substitution for efficient water splitting

The expanding requirement of energy-effective and cost-efficient water electrolysis has prompted studies of earth-abundant metal-based electrocatalysts. In this study, we study the typical substitution strategies of cation (Pt) or anion (Se) for modifying surface active sites or interphase engineering to tune electronic structure of bimetallic nickel molybdenum oxide hydrates (NiMoO4·xH2O), thus effectively improving catalytic properties toward hydrogen evolution reaction (HER) or oxygen evolution reaction (OER). Result of the cation substitution achieves PtSA–NiMoO4·xH2O catalyst with abundant doped Pt single atoms on surface, which promotes high HER activity with a small overpotential of 73 mV at a current yield of 10 mA cm−2 in alkaline medium. Meanwhile, Se–NiMoO4·xH2O catalyst, an outcome of the anion substitution approach, has unique interfaces of NiSe-NiMoO4 heterostructure and thus exhibits a desired overpotential of only 297 mV for OER. The combination of PtSA–NiMoO4·xH2O(–)//Se–NiMoO4·xH2O(+) couple results in a two-electrode electrolyzer cell, which requires a small cell voltage of 1.48, 1.54 and 1.59 V to deliver a response of 10 mA·cm−2 at 75, 50 and 25 °C, respectively, along with negligible performance decay during 50 h operation. These results highlight the potential of our catalyst engineering strategies to achieve high-performance green hydrogen production.

A phosphor-in-glass film prepared with a novel orange Lu2GdMg2AlSi2O12:Ce3+ phosphor and a cyan BaSi2O2N2:Eu2+ phosphor

The preparation of phosphor-in-glass (PiG) films containing orange and cyan phosphors is one of the possible ways to improve the color rendering index (CRI) and correlated color temperature (CCT) of white LEDs packaged with PiG films. Recently, by matrix ion substitution, we have synthesized a novel orange Lu2GdMg2AlSi2O12:Ce3+ phosphor. Then, we used a “coating and low-temperature sintering” method to prepare PiG films containing this novel orange phosphor and the commercial cyan BaSi2O2N2:Eu2+ phosphor on sapphire substrates. Combining these PiG films with blue LED chips, warm white LEDs with CRI above 90 and CCT below 4000 K can be obtained. This suggests that the PiG films containing cyan and orange phosphors are promising to improve the CCT and CRI of white LEDs packaged with PiG films.