Sr Site Research Articles

The Influence of Fe-Doping on the Structural, Electrical and Magnetic Behavior of Mechanically Activated SrTiO3 Ceramics

This research focused on the structural, dielectric and magnetic properties of Fe-doped strontium-titanate (SrTiO3) ceramics prepared from mechanically activated powders. A solid-state method was used for powder preparation with mechanical activation times of 10, 30 and 120min. The SrTiO3 ceramics were doped with various iron(III) oxide (Fe2O3) contents of 1.5wt%, 3wt% and 6wt%. X-ray diffraction analysis showed the presence of structure distortion due to ion substitution which caused changes in lattice parameter. For samples activated for 30 and 120min Fe ions were predominantly incorporated onto Sr sites for 3wt% Fe2O3, while for 6wt% Fe2O3 Fe ions were predominantly incorporated onto Ti sites. Microstructural analysis showed that the 120min activated sample (6wt% Fe2O3) had the highest homogeneity and bulk density (4.75gcm-3). Also, this sample exhibited multiferroic behavior as a consequence of the incorporation of Fe ions onto Ti sites in the structure, where magnetic properties are induced by doping without significantly impairing the dielectric properties. Based on these results, the optimal electrical and magnetic properties of SrTiO3 ceramics can be achieved by the appropriate choice of mechanical activation time and dopant concentration.

Theoretical Study of the Co‐doping Effects at Sr and Fe Sites on the Magnetic and Optical Properties of SrFe12O19

For the first time, the magnetic and optical (bandgap) properties of co‐doped Mg/Dy, Al/Dy, and Mn/Nd (SFO) at Sr and Fe sites are investigated using a microscopic model and the Green's function theory. It is shown that the co‐doping at both Sr and Fe sites can change the behavior of the magnetization which decreases by transition metal or nonmagnetic ion doping at the Fe site (with doping ions larger than the host Fe ions), but by additive co‐doping at the Sr site with rare‐earth ion (which ionic radius is smaller than that of Sr) the magnetization increases with increasing the co‐doping concentration. The bandgap energy decreases in the co‐doped SFO. The mechanism of this co‐doping effect is explained on microscopic level. It is due to the changes of the spin‐exchange interaction constants at the doped sites caused by the appearance of different strain by the doping with two ions. The theoretical results are compared with the existing experimental data and are in good qualitative agreement.

Assessing Drought Impacts on Gross Primary Productivity of Rubber Plantations Using Flux Observations and Remote Sensing in China and Thailand

Rubber (Hevea brasiliensis Muell.) plantations are vital agricultural ecosystems in tropical regions. These plantations provide key industrial raw materials and sequester large amounts of carbon dioxide, playing a vital role in the global carbon cycle. Climate change has intensified droughts in Southeast Asia, negatively affecting rubber plantation growth. Limited in situ observations and short monitoring periods hinder accurate assessment of drought impacts on the gross primary productivity (GPP) of rubber plantations. This study used GPP data from flux observations at four rubber plantation sites in China and Thailand, along with solar-induced chlorophyll fluorescence (SIF), enhanced vegetation index (EVI), normalized difference vegetation index (NDVI), near-infrared reflectance of vegetation (NIRv), and photosynthetically active radiation (PAR) indices, to develop a robust GPP estimation model. The model reconstructed eight-day interval GPP data from 2001 to 2020 for the four sites. Finally, the study analyzed the seasonal drought impacts on GPP in these four regions. The results indicate that the GPP prediction model developed using SIF, EVI, NDVI, NIRv, and PAR has high accuracy and robustness. The model’s predictions have a relative root mean square error (rRMSE) of 0.22 compared to flux-observed GPP, with smaller errors in annual GPP predictions than the MOD17A3HGF model, thereby better reflecting the interannual variability in the GPP of rubber plantations. Drought significantly affects rubber plantation GPP, with impacts varying by region and season. In China and northern Thailand (NR site), short-term (3 months) and long-term (12 months) droughts during cool and warm dry seasons cause GPP declines of 4% to 29%. Other influencing factors may alleviate or offset GPP reductions caused by drought. During the rainy season across all four regions and the cool dry season with adequate rainfall in southern Thailand (SR site), mild droughts have negligible effects on GPP and may even slightly increase GPP values due to enhanced PAR. Overall, the study shows that drought significantly impacts rubber the GPP of rubber plantations, with effects varying by region and season. When assessing drought’s impact on rubber plantation GPP or carbon sequestration, it is essential to consider differences in drought thresholds within the climatic context.

Mechanism of chromium poisoning on La0.5Sr0.5Co0.25Fe0.75O3 cathode and enhancing chromium tolerance using a novel anion doping strategy

Chromium poisoning the La1-xSrxCoyFe1-yO3(LSCF) cathode for solid oxide fuel cells is a severe issue that can lead to its electrochemical performance degradation. To clarify poisoning mechanism of chromium species and develop a novel anion doping strategy with enhancing chromium tolerance, the adsorption behavior of Cr species on LSCF and F-doping LSCF surface are explored by density functional theory (DFT) calculations. Our results indicate that CrO3 molecule prefers to be adsorbed on the La(Sr)O-terminated surface rather that the Co(Fe)O2-terminated LSCF(001) surface. The adsorption energies of CrO3 molecule are much larger than that of O2 molecules, implies that the CrO3 is more favorable to absorb on the LSCF surface. Bader charge analysis shows the CrO3 molecule behaves as an electron acceptor through an adsorption process. The adsorption of Cr atom is a weak physical adsorption for Sr site and La site and the Cr atom chemisorption is found to occur on hollow site and O site. In addition, F-doping efficiently improves chromium tolerance by weakening the adsorption strength of chromium species that poisons LSCF surface and this may be a feasible strategy to develop cathode for high performance solid oxide fuel cells.

Study on the possibility of band gap widening of thermoelectric semiconductor α-SrSi2 by isoelectronic elements incorporation

The material α-SrSi2 has considerable application potential as a near room temperature thermoelectric material. However, it has a very narrow band gap which can vanish due to impurities, defects, and grain boundaries. To obtain guidelines for controlling the band gap and improving the thermoelectric properties, we have studied the substitution of isoelectronic impurities (Mg, Ca, and Ba for Sr, and C, Ge, and Sn for Si) through first-principles calculations using the Gaussian-Perdew-Burke-Ernzerhof hybrid functional. From these calculations, it was found that:(1) The band gap change due to Ca, Ba, Ge, and Sn substitutions is almost the same as that predicted from the change in the lattice constant of pure α-SrSi2.(2) Substitution with C was energetically unfavorable and therefore high levels of substitution would be difficult to achieve. However, it was expected to increase the band gap, contrary to the prediction from the decrease in the lattice constant.(3) An increase in the Mg substitution of the Sr site from 0 at. % to 8 at. % caused a decrease in the lattice constant from 0 % to −1.189 %

Dielectric and magnetic response of mechanically activated Mn-doped SrTiO3 ceramics

This research was focused on the influence of manganese (Mn) incorporation at Sr and/or Ti sites on the microstructure, relative dielectric permittivity and specific magnetization of strontium titanate (SrTiO3) ceramics. A solid-state method was used for the preparation of mechanically activated (10, 30 and 120 min) Mn-doped SrTiO3 ceramics with various manganese dioxide (MnO2) weight percentages (1.5, 3 and 6 wt%). Rietveld's analysis showed that the mean crystallite size in doped-activated SrTiO3 ceramics is smaller than in undoped ceramics, which is a consequence of additional crystal structure distortion due to ion substitution. Changes in the Raman spectra indicated dopant incorporation in the SrTiO3 lattice. The microstructural analysis pointed out a decrease in the mean grain size with increasing dopant concentration and time of activation. The highest values of permittivity and magnetization were observed for Mn-doped SrTiO3 ceramic mechanically activated for 120 min. Based on all the above, the optimal electrical and magnetic properties of SrTiO3 ceramics can be achieved by the appropriate choice of mechanical activation time and dopant concentration.

Modification of Local Site Preference for Achieving Tunable Color Emission from Blue to Near-White in Sr3(PO4)2:Dy3+ Phosphor

The color tunability of Sr3(PO4)2:1%Dy3+ phosphor from blue to near white is studied at various annealing conditions. Higher temperature annealing promotes agglomerated rhombohedral (α) phase formation. Experimental and theoretical analysis reveal dopant preference at the low-symmetry Sr(II) site, altering electric (4F9/2→6H13/2) and magnetic (4F9/2→6H15/2) dipole transitions, thereby affecting the yellow-to-blue (Y/B) ratio. The luminescence intensity variation and color tunability are explained based on the local site symmetry and occupation probability of the dopant in the host lattice. An increase in the luminescence intensity up to an annealing temperature of 1200 °C, followed by quenching is observed due to the oxygen vacancies. Commission Internationale d'Eclairage (CIE) color coordinates of (0.31, 0.38), Correlated Color Temperature (CCT) of 6341 K, and color purity of 22.57% confirm the potential of Sr3(PO4)2:1%Dy3+ phosphor annealed at (1200 °C, 6 hrs) for white light generation. A probable photoluminescence mechanism involving 4f→5d→4f transitions in Sr3(PO4)2:1%Dy3+ is proposed.

Magnetic properties and coupled spin‒phonon behavior of M‒type Sr1-xSmxFe12O19 (0 ≤ x ≤ 0.15) nanoparticles

We thoroughly investigated the effects of Sm³⁺ doping on the magnetic, structural, hyperfine, and vibrational properties of Sr1-xSmxFe12O19 (0 ≤ x ≤ 0.15) nanoparticles, which were synthesized using the proteic sol-gel process. The Rietveld refined XRD patterns confirmed the presence of M-type SrFe12O19, alongside a minor fraction of α-Fe2O3. As Sm³⁺ doping increased, the unit cell volume fluctuated, decreasing from 691.73 ų at x = 0 to 690.67 ų at x = 0.10 and slightly rising thereafter. The incorporation of Sm³⁺ induced a conversion of Fe3+ to Fe2+, affecting lattice parameters and crystallinity. At x = 0.10, maximum crystallite size (56.48 nm) and X-ray density (4.83 g/cm³) were attained, alongside decreased microstrain, indicating improved crystallinity and reduced defects. However, at x = 0.15, an increase in microstrain suggested lattice instability. FTIR confirmed that bands in the range 400–600 cm⁻1 might be due to the stretching vibration of oxygen and metal (Fe–O) ions, confirming the formation of hexaferrite. Temperature-dependent Raman spectroscopy studies confirmed the presence of spin-phonon coupling in all samples in the ferrimagnetic transition at ∼725-735 K. Mössbauer spectroscopy elucidated that the substitution of Sr2+ by Sm3+ induced the most pronounced effect on the 12k, 4f2, and 2a sites, corroborating the evolution of the lattice constants and the fact that these three sites have Sr sites in their close vicinity. The room-temperature hysteresis loops exhibited narrow features, indicative of soft magnetic behavior. Saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) varied with Sm3+ doping content (x). Ms initially decreased from 62.62 emu/g and 22.03 emu/g at x = 0.00 to 54.96 emu/g and 19.63 emu/g at x = 0.10, respectively, and then increase to 59.77 emu/g and 21.86 emu/g at x = 0.15. Conversely, Mr and Hc showed a non-monotonic trend with x, suggesting complex interactions between dopant concentration and magnetic properties.

Heterostructure anion-groups guided design enabling customizable Eu2+ spectrum behavior in borophosphate☆

Definite emission color from rare-earth Eu2+ cannot be guaranteed in distinct hosts because its spectrum behavior is strongly dependent on surrounding microenvironment. Herein, we propose a strategy of heterostructure polyhedron BO3-PO4 substitution that can realize customizable and even predictable Eu2+ emission. Taking Sr3La(PO4)3:Eu2+ blue phosphor as host, we prepared a series of BO3-PO4 substitution-designed Sr3La(PO4)3−x(BO3)x:Eu2+ (SLP3−xBx:Eu2+) phosphors via solid-state reaction. Structural and spectral analyses demonstrate that substitution of PO4 with BO3 unit drives Eu2+ to migrate from original occupied Sr sites to unoccupied six-coordinated La sites, bringing out a brand-new broadband yellow-emitting peak at 530 nm, enabling an efficient spectrum tailoring from initial blue emission at 420 nm to white-light and then yellow. Strikingly, we find that the resultant Eu2+ spectrum behavior in as-prepared SLP3−xBx:Eu2+ and Eu2+-doped other borophosphate phosphors is highly similar (although they have different microenvironments). Such exciting findings indicate that proposed BO3-PO4 substitution-strategy possesses an ability of predicting emission by modulating Eu2+ site-selective occupation. Utilizing SLP3−xBx:Eu2+ (x = 0.1 and 0.4) phosphors, we fabricated optical temperature sensor and white LED prototypes, showcasing remarkable temperature sensitivity of Sr = 1.1%/K and good color rendering index (CRI) of 83. This work may aid the discovery of novel functional materials with specific, desirable physicochemical properties.

Theoretical Study of Electric, Dielectric, and Optical Properties in Ion Doped Multiferroic SrFe12O19 Nanoparticles.

Electric, dielectric, and optical (band gap) properties of pure multiferroic as well as La- and Ni-doped SrFe12O19 (SFO) (at different sites) are investigated using a microscopic model and Green's function technique. The concentration dependence of the polarization P is considered for substitution of rare earths ions on the Sr sites. For a small La ion doping concentration, x = 0.1, La-doped SFO is ferroelectric, whereas for a larger doping concentration, for example x = 0.5, it is antiferroelectric. The real part of the dielectric constant ϵ increases with an increasing magnetic field h. ϵ decreases with an increasing frequency and La dopants. Therefore, La-doped SFO is suitable for microwave application with a low dielectric constant. The magnetic properties of pure SFO NPs are also studied. Ni doping at the Fe site of SFO leads to enhanced ferroelectric polarization and dielectric constant. The band gap decreases or increases by substitution of Ni or In ions on the Fe site, respectively. The results reveal that the tuned band gap of Ni-doped SFO makes it a crucial candidate for optoelectronic and solid oxide fuel cell applications.

Atomic resolution microstructure study of Bi-doped SrTiO3

Intrinsic SrTiO3 is a quantum paraelectric, but moderately Bi-doped SrTiO3 exhibits dielectric frequency dispersion similar to relaxor ferroelectrics. In this paper, detailed electron microscopic studies of the microstructures of Bi-doped SrTiO3 samples were presented. It was found that the Sr sites were replaced by off-central Bi, resulting in tensile strain in the strontium titanate (STO) lattice. In the Bi-doped SrTiO3 samples, the valence of titanium mainly showed the Ti[Formula: see text] characteristic. According to the dielectric behavior and microstructure analysis, the polar nanoregions (PNRs) composed of strained SrTiO3 nanoclusters should be responsible for the ferroelectric relaxor behavior in samples with moderate Bi content.

Sc-doped Ba0.5Sr0.5Co0.8Fe0.2O3-δ cathodes for protonic ceramic fuel cells

Sc is used as a dopant to tailor the traditional Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) cathode for protonic ceramic fuel cells (PCFCs). Experiments and first-principles calculations are used in this study to explore the influence of Sc-doping on the performance of BSCF cathodes for PCFCs. Sc can only occupy the Co or Fe sites, and doping Sc at the Ba or Sr sites results in the formation of secondary phases. The use of Sc dopant reduces the high thermal expansion of traditional BSCF. More importantly, doping Sc into BSCF reduces the formation of oxygen vacancies while improving hydration and decreasing the proton migration barrier. Doping Sc at the Fe site outperforms doping at the Co site in terms of oxygen vacancy content, hydration capability, and proton migration ability. The new Ba0.5Sr0.5Co0.8Fe0.1Sc0.1O3-δ (Sc doped at Fe site) has a high fuel cell performance of 1666 mW cm−2 at 700 °C and a low polarization resistance of 0.033 Ω cm2. The fuel cell performance is superior to that of most BSCF-based PCFCs reported, indicating the efficacy of using the Sc-doping strategy to tailor BSCF and the importance of selecting the appropriate doping site.

Analysing the suitability of CaTiO3/Ca1–xSrxTiO3/SrTiO3 perovskite for fabrication of optoelectronic devices using QuantumATK tool: a study for electronic and optical properties

Calcium Titanate (CaTiO3) as a material has been researched for various applications like those in capacitors, piezoelectric devices and ceramic applications. Same has been possible owing to the exhibition of various characteristics of this material like high melting point (1,625 °C) and dielectric properties. However, only limited studies have been conducted to understand the impact of Strontium (Sr) doping and possibility of adopting this material into any kind of optoelectronic applications. This paper carries on an in-depth analysis on CaTiO3 and study effect of Sr as a dopant on its properties. Analysis has been carried out using Quantum ATK tool based on DFT approximations. CaTiO3 perovskite properties were studied by using the GGA (Generalized Gradient Approximation) and PBE (Perdew–Burke–Ernzerhof) functionals, which are used with the LCAO calculator. As a result of the inclusion of Sr at the Ca site, the electronic band structure of CaTiO3 was changed by the introduction of a gamma point. Bandgap of CaTiO3 was analysed to be dependent on the Sr site concentration and increased from 2.3 eV (Direct bandgap) to 2.3612 eV (Indirect bandgap), when Sr and Ca site concentration were equal, but it decreased with further increase in Sr site concentration to 1.7155 eV. Pure CaTiO3’s projected density of states changed after doping, providing evidence for the effects of the dopant on the system. As a result of an examination of the optical properties of both systems, it is found that CaTiO3 at 380 nm (close to infrared) exhibits an effective extinction coefficient (k) value of 0.78, whereas at 600 nm, the attenuation of light decreases to zero. This makes Sr doping in CaTiO3 another attractive candidate for optical devices in addition to its ability to change optical properties.

Designing novel tunable Mn-based inorganic oxyfluoride pigments

A high tunability of green-blue colors in the manganese-doped oxyfluoride Sr2.5A0.5Mn0.1MO4F (A = Ca, Sr, Ba; M = Al, Ga) and anion-deficient Sr2.5A0.5Mn0.1MO4-αF1-δ (A = Ca, Sr, Ba; M = Al, Ga) is reported, and the chromophores responsible for this intense pigmentation are investigated. The hues exhibited by these materials are quantified via diffuse reflectance UV/Vis spectroscopy and measurement of their direct band gaps via Tauc plot. It is shown that choice of A cation (A = Ca, Sr, Ba) and M cation (M = Al, Ga) for as-synthesized phases Sr2.5A0.5Mn0.1MO4F yield a wide range of green colors (band gap range 2.70–2.96 eV). Treatment of these phases under reducing conditions according to Sr2.5A0.5Mn0.1MO4-αF1-δ (A = Ca, Sr, Ba; M = Al, Ga) induces anion non-stoichiometry, shifting the observed colors to a wide range of blue/blue-purple hues (band gaps from 3.31 to 3.66 eV), showing potential as tunable inorganic blue pigments. Density field theory (DFT) calculations support the preferential occupation of the smaller 8-coordinate Sr(2) site by the substituted Mn2+ cation. X-ray absorption near-edge structure (XANES) data reveal more subtle nuances in the interplay between formal manganese oxidation state, crystallographic site and observed hue. In general, for as synthesized (green) Sr2.5A0.5Mn0.1MO4F (A = Ca, Sr, Ba; M = Al, Ga), the edge position in Mn K-edge XANES is consistent with mixed Mn3+-Mn4+ oxidation state whilst a clear pre-edge structure suggesting that Mn is present on a tetrahedral site. This would suggest that during the reduction step, Mn3+/Mn4+ is reduced to entirely Mn2+ and migrates from the tetrahedral to the Sr(2) lattice site.

A novel bismuth-activated Sr3NaSbO6 phosphor with multi-band switchable emission for NUV-pumped LEDs.

Multi-band emission characteristics open up more possibilities for the application of phosphors in LEDs. In this work, a novel Bi3+-activated Sr3NaSbO6 phosphor is developed. The Bi3+ occupation, luminescence properties and application in LEDs of the phosphor are investigated and discussed. There are Sr and Na sites in the crystal structure for Bi3+ substitution, corresponding to two different luminescence centers, which can be excited by commercial UV chips. By changing the excitation wavelength, Bi3+ in the two lattice sites can be excited separately, and a switchable multi-band emission can be obtained accordingly. The blue emission peaks at 450 nm, and the other emission has an ultra-wide full-width at half-maximum of 206 nm, which can cover a wider visible spectrum. All the results show that the phosphor has application prospects in LEDs.

Order and Disorder in Mixed (Si, P)–N Networks Sr2SiP2N6:Eu2+ and Sr5Si2P6N16:Eu2+

AbstractIn the field of nitride phosphors, which are crucial for phosphor‐converted light‐emitting diodes, mixed tetrahedral networks hold a significant position. With respect to the wide range of compositions, the largely unexplored (Si, P)–N networks are investigated as potential host structures. In this work, two highly condensed structures, namely Sr2SiP2N6 and Sr5Si2P6N16 are reported to address the challenges that arise from the similarities of the network‐forming cations Si4+ and P5+ in terms of charge, ionic radius, and atomic scattering factor, a multistep workflow is employed to elucidate their structure. Using single‐crystal X‐ray diffraction, energy‐dispersive X‐ray spectroscopy (EDX), atomic‐resolution scanning transmission electron microscopy (STEM)‐EDX maps, and straightforward crystallographic calculations, it is found that Sr2SiP2N6 is the first ordered, and Sr5Si2P6N16 the first disordered, anionic tetrahedral (Si, P)–N network. After doping with Eu2+, Sr2SiP2N6:Eu2+ shows narrow cyan emission (λmax = 506 nm, fwhm = 60 nm/2311 cm−1), while for Sr5Si2P6N16:Eu2+ a broad emission with three maxima at 534, 662, and 745 nm upon irradiation with ultraviolet light is observed. An assignment of Sr sites as probable positions for Eu2+ and their relation to the emission bands of Sr5Si2P6N16:Eu2+ is discussed.

Rational design of bimetallic sites in covalent organic frameworks for efficient photocatalytic oxidative coupling of amines

The conversion of organic compounds by photocatalysis under mild conditions is an environment-friendly alternative for organic transformations. In this work, the bimetallic covalent organic framework coordinated by Sr2+ and Fe2+ in the porphyrin centers with molar ratio of 2:1 (COF-Sr2Fe1) was synthesized through a two-step reaction. Under the synergistic regulation of Sr2+ and Fe2+, the separation of photogenerated charges and visible light absorption for COF-Sr2Fe1 were significantly promoted, and thus COF-Sr2Fe1 exhibited efficient photocatalytic performance towards benzylamine oxidative coupling reaction with a yield of 97 %, much higher than that of the nonmetallic covalent organic framework COF-366. Moreover, it was found that the Fe site displayed higher dehydrogenation ability and the Sr site displayed higher CN coupling ability through the density functional theory (DFT) calculations, thereby making the dehydrogenation and CN coupling steps more controllable for benzylamine oxidative coupling reaction by COF-Sr2Fe1. This work provides a strategy for designing efficient covalent organic frameworks photocatalysts, and helps to understand the oxidative coupling of amines more deeply.

Enhanced conductivity and weakened magnetism in Pb-doped Sr2IrO4

Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr2IrO4. It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x = 0.3 in Sr2−x Pb x IrO4. The mapping data obtained from energy-dispersive x-ray spectroscopy analyses give solid evidence that the Pb ions are uniformly distributed in the Sr2IrO4 matrix. The incorporation of Pb leads to a moderate depression of the canted antiferromagnetic ordering state. The electrical conductivity could be greatly enhanced when the Pb doping content is higher than x = 0.2. The present results give a fresh material base to explore new physics in doped Sr2IrO4 systems.

Effect of Cation Nonstoichiometry on Hydration and Charge Transport Processes in Yb-Doped SrZrO3 Perovskite-Type Proton Conductor for Ceramic Electrochemical Cells

The effect of Sr deficiency on the hydration process and ionic and electronic conductivity of Yb-doped SrZrO3 proton conductors with a perovskite-type structure was investigated. Dense SrxZr0.95Yb0.05O3-δ (x = 0.94–1.00) ceramics were prepared using solution combustion synthesis. Thermogravimetry and Raman spectroscopy methods were used to determine the concentration of bulk protonic species. Sr deficiency was found to enhance the hydration ability of the zirconate; however, lowering of Sr content to x = 0.94 deteriorated the proton uptake. The conductivity of the SrxZr0.95Yb0.05O3-δ series depending on the oxygen partial pressure at different humidities was studied by the four-probe direct current technique. Sr-deficient ceramics with x = 0.96 and 0.98 were shown to become purely protonic conductors in humid atmospheres at a temperature close to 500 °C. The ionic conductivity reaches its highest value at a Sr content of x = 0.98 (2 × 10−4 S cm−1 at 500 °C and pH2O = 3.17 kPa). The hydration behavior and transport properties of SrxZr0.95Yb0.05O3-δ are discussed in terms of the defect chemistry model that assumes the distribution of Yb ions over Sr and Zr sites at a large Sr deficiency.

Study on the stable and efficient white-emitting Bi/Tb/Eu tridoped single-phase borate Sr3YB3O9 phosphors

Several series of novel broad band white light emitting Bi/Tb/Eu tridoped in multiple lattice sites of single-phase Sr3YB3O9 (SYBO) borate phosphors, which covered almost all visible range through mixing the separate blue, green and red emissions from dopants of Bi, Tb and Eu, respectively, were successfully obtained by using the facile and conventional solid-state reaction method under air condition. Rietveld refinements based on XRD data together with the combination match of charge and ion radius for dopants of Bi, Tb, Eu and lattice cations of Sr, Y and B show that Bi is more inclined to replace the Sr site while Tb/Eu are more likely to enter the Y site, respectively. Through spectrum analysis of photoluminescence excitation (PLE), PL and decay lifetime, the efficient energy transfer (ET) from the Bi to both Tb and Eu, and from Tb to Eu are all testified via the dipole-dipole interactions, indicating that the non-rare-earth activator Bi is acting both as the blue luminescence center and ET sensitizer, while the Tb contributes both as ET bridge and green luminescence center to better connect the Bi and Eu. The optimal tridoped white emission SYBO phosphor appears good thermal stability, which could continue to have its PL intensity above 75% at 150 °C as compared with the original room temperature PL intensity. Altogether, the single-component SYBO:Bi/Tb/Eu phosphor could be well served as potential white light phosphor for n-UV pumped wLED devices.