Stable Temperature Range Research Articles

Exploring the Effect of Indoor Thermal Comfort using Iris Dampers: A Justification Study

This study explores the impact of fixed damper openings on indoor thermal comfort in a lab-scaled chamber. Experiments with maximum, medium, and minimum iris damper openings were conducted under various occupancy conditions. Results show that the maximum opening maintained temperatures close to the ideal 24°C with minimal fluctuations. In contrast, medium and minimum openings resulted in higher temperature variability and less efficient air distribution. Statistical analysis highlighted significant differences in temperature stability among the different damper settings. The maximum opening ensured a stable temperature range, while the minimum opening caused noticeable temperature stratification and discomfort, especially with more occupants. The findings indicate that fixed damper openings are inadequate for maintaining consistent thermal comfort due to their lack of adaptability. This underscores the need for advanced control systems that can dynamically adjust damper positions to ensure optimal indoor temperature regulation and improve energy efficiency.

A first-principles study of helium diffusion in aragonite under high pressure up to 40 GPa

Helium diffusion in carbonates under mantle pressure is crucial for understanding thermal and chemical evolution of mantle. Based on the density functional theory (DFT) and the the climbing image nudged elastic band (CI-NEB) method, we performed first-principles calculations of diffusion characteristics of helium in perfect aragonite crystal under high pressure to 40 GPa. Our results show that He diffusion behaviors are controlled by pressure, temperature and crystal size. The activation energy increases, and the diffusion coefficients decrease significantly under high pressure. Ea[100] increases from 176.02 kJ/mol to 278.75 kJ/mol, and Ea[001] increases from 195.89 kJ/mol to 290.43 kJ/mol, with pressure increasing from 20 GPa to 40 GPa. At 700 K, the diffusion coefficients at 40 GPa is 7 orders of magnitude lower than that at 20 GPa; and at 1000 K it decrease 5 orders of magnitude. To ensure that at least 90% helium is not lost, we synthesized the temperature obtained from cooling and heating processes and derive the 'stable temperature range' for helium in aragonite. The obtained results show that the stable temperature range is 22–76 ℃ at 0 GPa and 641–872 °C at 40 GPa, for the crystal of 100–2000 μm size. Besides, the travel time of helium in aragonite under high pressure increases rapidly with pressure increasing. Our calculations indicate that helium can be quantitatively retained in aragonite in the deep mantle as long as the temperature is in the 'stable temperature range'. These results have certain implications for exploring the evolution of mantle and the storage of helium within it.

Low temperature coefficient of frequency AlN Lamb wave resonator using groove structure between interdigital transducers

The lithographically tunable and small size features of Lamb wave resonators (LWRs) take a bright future for their use in high frequency narrow band filters. Resonant frequency drift due to temperature variation has a large impact on the narrower passband and a temperature coefficient of frequency (TCF) closer to 0 can broaden the stable temperature range of the resonator. This paper proposes a method of etching grooves in the area of the piezoelectric layer not covered by the Interdigital transducer (IDT) electrodes to improve the temperature stability of the Lamb resonator. Through the finite element method and theoretical analysis, the phase velocity, group velocity, and TCF dispersion curve of different modes of the resonator with groove structure were determined. The reason for the change of TCF under different normalized thicknesses of AlN was explained through the conversion of the LWR from a contour mode resonator (CMR) to a Cross-Sectional Lamé Mode Resonator. Simulation and test have shown that etching grooves have the effect of reducing TCF by adjusting the electromechanical coupling coefficient. The test shows that 205 nm-depth grooves can lower the TCF of the S0 mode IDT-Open LWR from −13.3 to −5.1 ppm/°C and S1 mode from −36.8 to −9.0 ppm/°C, respectively. The TCF of S0 and S1 mode LWRs decreased by 61.7% and 75.5%, respectively, after 205 nm groove etching. The groove etching method greatly raises the temperature stability of the LWR, enabling Lamb wave filters to operate stably over a wider temperature range.

Measurement of Diffusion Coefficients and Assessment of Atomic Mobilities in HCP Mg-Ag-Sn Alloys

Reliable thermodynamic and kinetic databases are essential for designing and developing novel magnesium (Mg) alloys for elevated-temperature applications in the automotive and aerospace industries. This study investigated diffusion behaviors of HCP Mg-Ag-Sn alloys by four sets of three diffusion couples annealed at 450, 500, and 550 °C, respectively. Interdiffusion and impurity diffusion coefficients at the three annealing temperatures were extracted using the forward-simulation method. The determined diffusion coefficients, combined with prior results in the literature, were then used to assess atomic mobilities for the HCP phase of the Mg-Ag-Sn system. This assessment was conducted using the DICTRA and the TCMG5 thermodynamic database within the Thermo-Calc software. Comprehensive comparisons between calculated and experimental diffusion coefficients yielded an excellent agreement. The atomic mobilities were also further validated by appropriate predictions of concentration profiles and diffusion paths observed in independent diffusion couple experiments performed at 525 °C for 18 hrs. It has been found that the addition of Sn and Ag both increase the diffusivity of Ag in HCP Mg and Sn in HCP Mg in the stable temperature range of HCP Mg, respectively. This improved understanding of the kinetics in the Mg-Ag-Sn ternary system is essential for controlling diffusion-dependent properties such as coarsening and, therefore, the mechanical properties of Mg-Ag-Sn alloys at elevated temperatures.

Dual-drive energy conversion plasmonic Ag@MXene thermal management textiles inspired by bearing structure

Multifunctional wearable textiles can simulate human perception and convert it into visual data, which has advanced application prospects. As an important branch, thermal management wearable textiles have been widely concerned in the aspects of thermal insulation, flame retardant, photothermal anti-icing, electrothermal deicing and even water evaporation. Here, inspired by the bearing structure, we simply soaked the PET textile in Ag@MXene hybrid solution several times to form a Ag@MXene conductive network with Ag NPs as the connection point on the textile fiber, and finally carry out hydrophobic modification. Based on plasma effect, the synergistic action of Ag NPs and MXene enhances the photothermal response of the material. In addition, the addition of Ag NPs effectively reduces the stacking between MXene layers and forms a Ag@MXene conductive network with Ag NPs as the connection point on the textile fibers. The stable temperature range of PDMS/Ag@MXene PET textile is 70–80 °C under one solar illumination intensity, and the stable temperature of PDMS/Ag@MXene PET textile can reach 117 °C at a constant voltage of 3 V. Based on the excellent thermal effect, this textile achieves photothermal anti-icing, electric thermal de-icing, keeping warm and removing sweat. The textile has a water evaporation efficiency of about 0.58 g h−1, which can achieve excellent anti-sweat function. Finally, the textile also achieved rapid flame retardant within 7 s. PDMS/Ag@MXene PET textile processes excellent photothermal and electrothermal conversion ability, acid/water stability and flame retardant ability, and has promising application prospects in thermal management textiles such as deicing and anti-icing, fire prevention, warmth and water evaporation.

Stable and wide temperature range superelasticity in an Mo-doped nanocrystalline Ni–Ti–Mo shape memory alloy

The phase transformation and superelastic behavior of nanocrystalline Ni48Ti50Mo2 alloy wires were investigated. Nanocrystalline (NC) alloys were obtained via severe plastic deformation of cold-drawing followed by annealing at low temperatures. The results indicate that the NC Ni48Ti50Mo2 undergoes a single-step B2→R phase transformation and a two-step B2→R→B19′ phase transformation in coarse crystals (CG). The NC alloy wire exhibits 8 % recoverable strain under a tensile stress of 1.1 Ga and superelasticity exists in a wide temperature range from −60 °C to 100 °C. After 50 cycles of tension fatigue testing, the superelastic upper plateau stress reduction rate is 7 % with almost no residual strain accumulation, which has excellent superelastic stability compared with fine crystals and coarse crystals. Transmission electron microscope (TEM) reveals an average grain size of 20 nm. The stable superelasticity is attributed to the nanocrystalline reinforced matrix, which hinders dislocation generation and slip.

Improved energy storage performance and thermal stability of hafnium-substituted strontium sodium niobate tungsten bronze ceramics.

Dielectric capacitors are widely used in the field of pulsed power systems owing to their ultra-fast charge and discharge capacity; however, considering the complex environment they face in practical applications, how to further improve their thermal stability is an urgent issue that needs to be solved. Tungsten bronzes have the potential to broaden the temperature stability range owing to their unique structure, but only few studies have focused on them. Herein, lead-free Sr4-x La x Na2Hf x Nb10-x O30 ceramics with a tungsten bronze structure were synthesized, and their energy storage properties were comprehensively characterized. With proper Hf substitution in the B site and rare earth substitution in the A site, significantly enhanced relaxor behavior is induced, leading to a broad plateau of the dielectric curve, slim polarization-electric field loop, high energy storage efficiency and stable capacitive performance over a wide temperature range. In addition, an improved microstructure with fewer defects, decreased average grain size, increased band gap and resistance were obtained, which benefit to the increase in breakdown strength and energy storage density. Finally, improved energy storage performance and thermal stability were achieved for the compounds, with W total = 3.6 J cm-3, W rec = 2.9 J cm-3, η = 80% and stable temperature range = 20-160 °C. Thus, the current system is a promising candidate for application in temperature-stable dielectric capacitors.

Experimental study of characteristics of a novel waste-modified phase change material with paraffin wax and raw fly ash

Thermal energy storage systems (TES) can fully utilize solar energy by storing excess and using it when required. Latent heat storage systems (LHS) have gained popularity due to their simplicity and high storage capacity. The present work deals with the development of a waste-modified phase change material (PCM) with raw fly ash (RFA) (a byproduct of the clay brick industry). The base or parent PCM is selected as paraffin wax due to its easy availability and nontoxic nature. Some characterization methods like XRD, FTIR, and DSC were applied to study the prepared composite PCM’s different surface, thermal, and chemical properties with 1 wt% of fly ash particles. Good compatibility among the constituents is evident from the XRD and FTIR spectra. There are minimal deviations of 1% and 2% in melting and freezing latent heat, respectively, compared to pristine paraffin wax, as evident from DSC analysis. The thermal reliability of the developed composite is apparent from the constant properties as shown in FTIR and DSC analyses after 100 repeated heating/cooling cycles. This waste-modified PCM with desirable characteristics like thermal reliability and stable temperature range can be an effective energy storage medium, ensuring proper reuse and recycling of wastes like fly ash particles.*

A flexible supercapacitor with high energy density and wide range of temperature tolerance using a high-concentration aqueous gel electrolyte

As the demand for a wide range of wearable devices increases, extensive effort is devoted to developing high-performance flexible energy storage devices such as batteries and supercapacitors. Of particular interest, flexible supercapacitors using aqueous electrolytes have high application potential owing to their many advantages including low cost, harmlessness to the human, and environmental safety compared to others using electrolytes such as ionic liquids and organic electrolytes. However, poor temperature tolerance and narrow operation voltage window have hindered the practical application of aqueous supercapacitors. In this study, we report on a wide temperature-tolerant flexible aqueous supercapacitor featuring high electrochemical performance designed by a deliberate selection of electrode materials and electrolytes. As a flexible electrode, three-dimensional microporous graphene foam coated with conducting polymer Polypyrrole (PPy) is used to enhance capacitance up -to 90.0 F/g by increasing the surface area and inducing the pseudo-capacitance of PPy. As a gel-type electrolyte, a high-concentration NaClO4 is mixed with Polyvinyl alcohol to enlarge the voltage window to 1.8 V and a stable temperature range from -25 to 80°C, even under repetitive bending deformation. The fabricated supercapacitor exhibits a superior energy density of 37.4 Wh kg−1 and maintains 92.0% of initial capacitance at room temperature after three repeated cycles of cooling/heating across a wide temperature range over 100°C. This work suggests a high potential application of the fabricated supercapacitor as an eco-friendly and stable energy storage system for powering diverse wearable devices under various conditions.

Antimony-Triggered Tunable White Light Emission in Lead-Free Zero-Dimensional Indium Halide with Ultrastable CCT of White Light Emitting Diodes.

A highly efficient and easily tunable luminescence is significant for solid-state luminescent (SSL) materials. However, achieving a photoluminescence quantum yield (PLQY) close to unity and tuning the emission remain challenging tasks. Metal doping strategies enable resolution of these issues. Herein, we report the preparation of a novel organic-inorganic lead-free indium-based metal halide hybrid (MP)3InCl6•EtOH (MP = C4H10ON) with a typical zero-dimension structure. When excited at 320 nm, (MP)3InCl6•EtOH exhibits a dual emission band at 420 and 600 nm, which originates from the organic cation [MP] and the [InCl6]3- octahedral unit. The photoluminescence can be significantly enhanced through Sb3+ doping, resulting in an increase in PLQY from 0.78% to near unity. Multiple emission color tunings have been achieved by regulating the Sb doping level and the radiation wavelength, resulting in a change in emission color from blue → white → orange. Optical characterizations reveal that the significantly enhanced emission centered at 600 nm can be attributed to more efficient absorption, closely associated with an additional 1S0 → 3P1 transition in the inorganic octahedron [In(Sb)Cl6]3- due to Sb3+ doping. With its excellent optical performance, a white light emitting diode (WLED) has been successfully fabricated by coating the mixture of (MP)3InCl6•EtOH:15%Sb3+ with blue phosphor BaMgAl10O17:Eu2+ onto a UV LED chip. The WLED device exhibits perfect white light emission with regard to the International Commission on Illumination (CIE) coordinates of (0.36, 0.34). Significantly, the WLED device maintains a stable correlated color temperature (CCT) range of 4119-4393 K and CIE coordinates (x: 0.37-0.34, y: 0.35-0.33) as the driven current varies from 20 to 200 mA, demonstrating outstanding stability across different power levels. This work not only presents a novel system for achieving remarkably enhanced luminescent performance and tuning emission bands in 0D metal halides but also represents a significant step toward achieving resistance to color drifting for stable WLEDs.

Colossal permittivity and low loss in (In0.5Ta0.5)0.1Ti0.9O2 ceramics with a stable temperature range of X9D

Colossal permittivity and low loss in (In0.5Ta0.5)0.1Ti0.9O2 ceramics with a stable temperature range of X9D

Integrated Thermoelectric Design Inspired by Ionic Liquid Microemulsion-Based Gel with Regulatable Dual-Temperature Responsiveness

The concept and principles of chromatic engineering of electrolytes have demonstrated charming prospects for constructing pluralistic electrochromic devices. Here, we develop a synthetic design bearing thermochromic and electrochromic behaviors based on the ionic liquid (IL) microemulsion-based gel, driven by the intrinsic thermodynamic stability of microemulsion and ionic conductivity of IL. The prepared gel can tune light-scattering behaviors as the droplet expanded or aggregated when the temperature is out of its thermodynamically stable temperature range. Not only that, oil-phase IL ([EMIM]TFSI) as well as introduced LiCl and LiTFSI endows it with satisfactory ionic conductivity, making it able to be utilized as a free-standing electrolyte layer for the electrochromic smart window. Therefore, the fabricated smart window based on this gel and WO3 electrochromic layer successfully realizes dual-stimuli responsiveness for both temperature and electric field, possessing energy-saving combined with privacy protection function. In addition, the component compatibility of microemulsion allows the harmonious introduction of hydrophilic antifreeze moisturizer ethylene glycol (EG) and hydrophobic ultraviolet absorber 2-hydroxy-4-(octyloxy)benzophenone (2H4MBP), which further promotes the multifunctional integration of a smart window for the strengthened safety factor, anti-freezing, anti-drying, and anti-UV capabilities. Finally, we extend the application of the IL microemulsion-based gel to an ionic writing plate based on the same electrochromic mechanism. In brief, this innovative preparation method paves the way for multifunctional electrochromic devices.

Numerical Investigation of Cooling Characteristics of a Double-sided Composite Impeller with a New Micro Gas Turbine

In order to achieve a micro gas turbine engine with higher thermal cycle parameters and higher aerodynamic performance, a double-sided composite impeller has been designed innovatively based on structures combined, thermal cycle process integration, and existing impingement cooling technology with the help of additive manufacturing technology, which is expected to increase the turbine inlet temperature and break the material limit. The double-sided composite impeller is numerically simulated by the method of gas-thermal coupling. The results showed that: First, compared with the turbine without cooling, the maximum turbine wall temperature and average turbine wall temperature of the turbine with impingement cooling technology decreased by more than 166.33K and 213.79K, respectively, and the minimum cooling efficiency and the average cooling efficiency of the turbine with impingement cooling technology increased by more than 34.32% and 46.8% respectively. Second, the physical property differences of nickel alloy materials in the same category have no obvious influence on the cooling characteristics of turbines. Finally, for GH4220 material, the turbine inlet temperature can be increased by more than 520K when the turbine material is kept in a stable working temperature range. This study opens the way for the higher turbine inlet temperature or the use of low-cost, lightweight materials such as titanium alloys.

Formation and Structural Characterization of Spinel‐Phase Zn2TiO4 Synthesized in a High‐Temperature Solution Approach

AbstractSpinel phase Zn2TiO4 powders were prepared by high‐temperature solution, which is a kind of molten salt (such as KCl melt). The effect of Zn2TiO4 synthesis was explored under different holding time, preparation temperature and the mass ratio of salt to raw material in KCl melt. Through experimental analysis, the synthesis temperature range of Zn2TiO4 phase in KCl molten salt system was from 800 to 1000 °C. Compared with the traditional solid‐state reaction, the stable temperature range of Zn2TiO4 phase in KCl molten salt system was wider. The HRTEM image analysis of calcined product was consistent with the XRD result. The TEM analysis showed that the average particle size of Zn2TiO4 powder was 200 nm. The crystallinity of Zn2TiO4 increased with increasing sintering time and Zn/Ti molar ratio. Compared with LiCl+KCl and LiCl melts, the crystallinity of Zn2TiO4 powder synthesized in KCl molten salt system was better. It is determined that the high‐temperature solution (KCl melt) can be successfully applied for large‐scale synthesis of spinel phase Zn2TiO4.

Life-history characteristics and climate correlates of dioecious plant species in central southern Australia

Context The proportion of dioecious species can vary considerably among climates and habitats. However, studies often involve isolated communities or large diverse areas and fail to capture how proportions vary across diverse landscapes.Aims To identify (1) life-history associations of terrestrial dioecious plant species in central southern Australia, (2) whether proportion of dioecy varies spatially across central southern Australia, and (3) whether proportion of dioecy is correlated with life-history and/or climate factors.Methods Species growth form, pollination mechanisms and seed-dispersal features were extracted from herbarium databases to determine potential dioecy-linked traits. Distribution data for native terrestrial species in 66 Interim Biogeographical Regionalisation of Australia subregions were extracted from the Australasian Virtual Herbarium to calculate the proportion of total native species richness that are dioecious. Climate data for each subregion were also obtained from Terrestrial Ecology Research Network databases to investigate relationships among climate, life-history traits and dioecy.Key results Woodiness, abiotic pollination and endozoochory were more prevalent in dioecious than non-dioecious taxa. Proportion of dioecy ranged from 1.7% to 8.5% among subregions and correlated negatively with annual temperature range, January to March rainfall and precipitation seasonality and with average annual daily mean, minimum, maximum and average annual minimum temperature. The highest-ranked models of dioecy incorporated the additive effects of the relative proportion of woody species and either annual temperature ranges, January to March rainfall or average annual daily maximum temperature.Conclusions Dioecy was associated with woodiness, abiotic pollination and endozoochory, in line with studies of other flora, with the model of stable temperature range and woodiness being the highest-ranked model of dioecy.Implications Areas with higher proportions of dioecy can be targeted for future investigations into dioecious plant ecology to aid conservation and ecosystem management.

Thermal expansion and microstructure evolution of atmospheric plasma sprayed NiCrAlY bond coat using in-situ high temperature X-ray diffraction

The paper focuses on in-situ high-temperature X-ray diffraction (HT-XRD) study on atmospheric plasma sprayed NiCrAlY coating. The sample was in-situ heated from 25 °C to 1150 °C in a controlled atmosphere (3 × 10−4 bar), and the corresponding X-ray diffraction patterns for different temperatures were recorded. The effect of temperature on crystallite size, lattice strain, and coefficient of linear thermal expansion was studied. Major phases identified are γ-Ni, γ’-Ni3Al, β-NiAl, and α-Cr. The formation of stable α-Al2O3 and spinel was found above 1000 °C. The transformation of β to γ’ and γ phase was observed as a function of temperature. The equilibrium phases and the thermal expansion of disordered Face Centered Cubic (FCC) and Body Centered Cubic (BCC) phases were predicted and supported by Thermo-Calc prediction for the stable temperature range. Results showed that the non-equilibrium microstructure produced by thermal spray process did not alter the thermal expansion behaviour. In-situ treatment resulted in microstructure and elemental homogenization. The thermal expansion and mechanism of phase evolution were discussed.

Synthesis and characterization of low-temperature lithium-ion conductive phase of LiX (X=Cl, Br)-Li3PS4 solid electrolytes

A new class of sulfide electrolytes, (1-x)LiCl-xLiBr-2Li3PS4 (x = 0, 0.25, 0.50, 0.75, and 1.0), was synthesized, and characterized their stable temperature range, ionic-conductivity and applicability for all-solid-state lithium metal battery. The optimal heat-treatment temperature of the synthesis process is relatively low, i.e., 200 °C. Ionic conductivity of the electrolyte increases with increasing LiBr ratio, and maximum ionic conductivity at 25 °C is 1.7 mScm−1 with x = 0.75. At higher heat-treatment temperature, above 250 °C, a low-ionic-conduction crystalline phase appears in the electrolyte, and at that time, ionic conductivity decreases to a similar value to that of the amorphous precursor used in the synthesis process. Since the electrolyte does not contain a transition metal, it is applicable to the lithium-metal secondary system. A reversible lithium deposition-stripping reaction was demonstrated by cyclic voltammogram, the results of which indicate that the electrolyte is applicable to a typical 4-V rechargeable lithium-metal secondary system. The Coulombic efficiency of the first charge-discharge cycle is approximately 75%, and reversible capacity of 185 mAhg−1 was verified by a Li/0.25LiCl-0.75LiBr-2Li3PS4/NCA pelletized-cell test. It is concluded from these results that the proposed low-temperature-synthesized sulfide electrolytes will reduce energy consumption for material production, and such a low-carbon-footprint process meets the demand of the future sustainable society.

High energy storage and thermal stability under low electric field in Bi0.5Na0.5TiO3-modified BaTiO3-Bi(Zn0.25Ta0.5)O3 ceramics

Dielectric energy storage capacitors have been comprehensively investigated for application in advanced electronic systems. Compared to other types of ceramic capacitors, BaTiO3-BiMeO3 lead-free composite relaxor ferroelectric ceramics (where Me represents trivalent or trivalent composite ion) are excellent dielectric energy storage candidates in pulsed power fields. However, the properties of most existing BT-based energy storage ceramics are not satisfactory in some practical aspects, and feasible guidance on efficient composting material systems with large recoverable energy storage density (Wrec) for ultralow electric fields is lacking. Herein, for the first time, lead-free relaxor ferroelectric (1-x)[0.9BaTiO3-0.1Bi(Zn0.25Ta0.5)O3]-xBi0.5Na0.5TiO3 ceramics with x = 0, 0.1, 0.2, 0.3, and 0.4 were synthesized via composite strategy using the traditional solid-state process. The used strategy combined the complementary advantages of both BT-BZT and BNT to greatly increase the saturation polarization (Ps) and shift the stable temperature range of permittivity to high-temperature region, achieving higher energy storage density and improved temperature stability. Optimum energy storage performances with a high Wrec of 4.18 J/cm3 and comparatively high η of 84.01% were simultaneously achieved in the relatively low electric field of 230 kV/cm. Moreover, the ceramic obtained at x = 0.3 showed excellent temperature stability with the change rate of Wrec < 5% and η < 6% throughout a broad temperature range (20 °C ∼ 170 °C). This ceramic (x = 0.3) simultaneously possesses superior pulse performance, exhibiting the t0.9 of 232 ns and Wdis of 2.51 J/cm3. Overall, the employed composite strategy design is effective for obtaining energy storage capacitors with excellent performance for future advanced pulsed power devices.

Hydration process of β-MoO3 powder prepared by pulsed wire discharge method

The hydration of β-MoO3 and α-MoO3 powders was investigated through powder exposure experiments at 24 ℃ in the air with a relative humidity of 53%. X-ray diffraction results showed a hydrated phase of MoO3·0.34H2O in only exposed β-MoO3 powder, while the α-MoO3 powder maintained its initial phase. By thermogravimetry-differential thermal analysis and mass spectrometry measurements and the dehydration experiments, the stable temperature range of the hydrated phase made by β-MoO3 was identified below 285 °C, and above this temperature, the hydrated phase transformed back to the original β-MoO3 phase. The other analysis methods using field-emission scanning electron microscopy and field-emission transmission electron microscopy were also used to determine powders’ morphology and size and to confirm phases from their lattice images. To the best of our knowledge, this is the first report on the formation of the hydrated phase by exposing β-MoO3 powder in the humid air.

Enhancing the Photoluminescence Property of Pr3+ Ions by Understanding the Polymorphous Influence of the K3Lu(PO4)2 Host.

Adjusting the local coordination environment of lanthanide luminescent ions is a useful method to manipulate the relevant photoluminescence (PL) property. K3Lu(PO4)2 is a phase-change material, and according to the stable temperature range from low to high, the related polymorphs are phase I [P21/m, coordination number (CN) of Lu3+ = 7], phase II (P21/m, CN = 6), and phase III (P3̅, CN = 6), respectively. Based on the temperature-dependent PL analysis of K3Lu(PO4)2:Pr3+, we find that Pr3+ ions occupy the noninversion sites (Cs) in the two low-temperature phases but preferentially enter into the inversion ones (C3i) in phase III. Compared to Pr3+-doped phase I (78 K), Pr3+ ions in phase III (300 K) manifest a weaker fluorescence intensity (170-fold lower). To enhance the room-temperature PL property of K3Lu(PO4)2:Pr3+, a polymorphous adjustment strategy was proposed by the use of the ion-doping method. By introducing the Gd3+ ions into the lattice, Pr3+-doped phase I is successfully stabilized to room temperature, manifesting a 27-fold fluorescence increase in comparison to K3Lu(PO4)2:Pr3+ (0.1 at. %). The finding discussed in this study highlights the significance of site engineering for luminescent ions and also presents the application value of phase-change hosts in the development of high-performance luminescent materials.