Polycrystalline Form Research Articles

Morphology engineering of low-temperature-synthesized aluminum nitride

We have developed an aluminum nitride (AlN) manufacturing method that operates below the melting point of aluminum. To examine the nucleation and growth mechanisms of AlN during the synthesis process, we used a variety of characterization techniques, including high-resolution transmission electron microscopy and rapid Fourier transform, which highlighted the development of its single-crystal and polycrystalline forms. The microstructural investigation showed that nitridation began with forming AlN shells on the surface of aluminum particles. Subsequently, volume nitridation occurred by transforming a single aluminum particle into either polycrystalline AlN with a columnar structure or single-crystal AlN. In addition, various interesting morphologies were observed during the microstructural investigation of low-temperature synthesized AlN, including truncated dodecahedrons, nanowires, particles, pillars, plates, and other polyhedral shapes. The study's microstructural findings provide crucial data on the AlN particle formation process, offering valuable insights expected to deepen understanding and expand the applications of AlN. Therefore, the consequence of this study is expected to make a meaningful contribution to understanding the formation mechanism of the particle type of AlN.

Synthesis and structural characterization of new perovskite phases, Ba2Bi0.572TeO6± δ and SrLa2NiFeNbO9

Ba2Bi0.572TeO6± δ and SrLa2NiFeNbO9 ceramics were prepared in polycrystalline form by conventional solid-state reaction techniques in air. The crystal structures of the title compounds were determined at room temperature from X-ray powder diffraction (XRPD) data using the Rietveld method. The Ba2Bi0.572TeO6± δ structure crystallizes in a triclinic space group I–1 with unit-cell parameters a = 6.0272(2) Å, b = 6.0367(1) Å, c = 8.5273(3) Å, α = 90.007(7)°, β = 90.061(2)°, and γ = 90.015(4)°. The tilt system of the BiO6 and TeO6 octahedra corresponds to the notation a–b–c–. The crystal structure of the SrLa2NiFeNbO9 compound adopts an orthorhombic Pbnm space group with lattice parameters a = 5.6038(5) Å, b = 5.5988(4) Å, and c = 7.9124(6) Å. The BO6 octahedra (B = Ni/Fe/Nb) sharing the corners in 3D. Along the c-axis, the octahedra are connected by O(1) atoms of (x,y,1/4) positions; while in the ab-plane, they are linked by O(2) atoms of (x,y,z) positions. The bond angle of B–O1–B is 168.7° and that of B–O2–B is 156.3°. The octahedral lattice corresponds to the tilt pattern a–a–c+; it indicates that the octahedra tilt out-of-phase along the a,b-axes and in phase along the c-axis.

PHYSICOCHEMICAL CHARACTERISATION OF SUVARNA BHASMA AND SUVARNA PRASHA USING ADVANCED TECHNIQUES

Background: Suvarna Prashana is an ancient Indian practice that boosts immunity, intelligence, memory, complexion, and virility and prevents infections in children. However, the characterisation of the drug is very limited. Material and Method: In this study, the physicochemical characterisation of Suvarna Bhasma is done with Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive Xray Analysis (EDAX ), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Suvarna Prash containing 15 mg of Suvarna Bhasma mixed with 0.25 ml of ghee and 0.75 ml of honey is characterised with Fourier Transform Infrared Spectroscopy (FTIR) with Suvarna Bhasma. Results: SEM revealed that gold particles of Suvarna Bhasma ranged from 27 nm - 8.1 µm and formed spherical aggregates of varied sizes with rough surfaces. EDAX suggested that Suvarna Bhasma contained Gold (86.3%), Oxygen (3.14%), and Carbon (10.52%). TEM reported that the particle size ranged from 2.2 to 18.9 nm, which existed in polycrystalline form as suggested by XRD. XPS confirmed the elemental state of gold Au(0), Silver-Ag +oxidation state, Carbon C-C, C=O, and C-N, where carbon is bonding with carbon, oxygen and nitrogen. FTIR revealed that Suvarna Bhasma alone had a single functional group of alkynes. When Suvarna Bhasma was triturated with honey and ghee, many functional groups were added to Suvarna Bhasma, i.e. fats, carbohydrates and amino acids. Conclusion: In this novel study, FTIR of Suvarna Prasha is reported for the first time, and it can be used as a fingerprint for drug identification. Also, it proves that Suvarna Bhasma, used in the current study, is a pure form of gold without heavy metals like mercury.

Enhancement of Thermoelectric Performance through Transport Properties Decorrelation in the Quaternary Pseudo-Hollandite Chalcogenide Rb0.2Ba0.4Cr5Se8.

The novel quaternary compound Rb0.2Ba0.4Cr5Se8 was synthesized and characterized in both single crystal and polycrystalline forms. Crystallizing in the monoclinic crystal system (space group C2/m, cell parameters a = 18.7071(4) Å, b = 3.6030(1) Å, c = 8.9637(3) Å, β = 104.494(2)°) and isostructural to pseudo-hollandite compounds, it features mixed Rb and Ba occupancy within its one-dimensional channels. High-temperature X-ray diffraction revealed no decomposition up to 973 K, and the thermal expansion coefficient at 300 K was determined to be 2.6(1)·10-5 K-1. Spin-polarized density functional theory (DFT) calculations showed that the density of states for Rb0.2Ba0.4Cr5Se8 is more polarized than that of Ba0.5Cr5Se8, resulting in a higher Seebeck coefficient, which was experimentally confirmed to reach a peak value of 400 μV·K-1 at 620 K. Resistivity measurements indicated a degenerate semiconducting behavior below 550 K, with a resistivity peak of 100 mΩ·cm at that temperature, leading to a maximum power factor of 0.21 mW·m-1·K-2. Thermal conductivity measurements indicated low values around 0.8 W·m-1·K-1 in the 300-900 K range, resulting in a thermoelectric figure of merit of 0.22 at 873 K. Decorrelated transport properties observed in this double-inserted pseudo-hollandite compound make Rb0.2Ba0.4Cr5Se8 a good example of beneficial synergistic effects for higher thermoelectric performance.

High tolerance of the superconducting current to large grain boundary angles in potassium-doped BaFe2As2

Superconducting magnets based on high-temperature superconductors (HTSs) have become critical components in cutting-edge technologies such as advanced medical applications. In HTSs, weak links of superconductivity are inevitable at high-angle grain boundaries (GBs). Thus, two adjacent grains should be crystallographically aligned within the critical angle (θc), for which the intergrain critical current density (Jc) starts to decrease exponentially. The θc of several iron-based superconductors (IBSs) is larger than that of cuprates. However, the decreases in both θc and intergrain Jc under magnetic fields for IBSs are still substantial, hampering their applications in polycrystalline forms. Here, we report that potassium-doped BaFe2As2 (Ba122:K) exhibits superior GB performance to that of previously reported IBSs. A transport Jc of over 0.1 MA/cm2 across [001]-tilt GBs with misorientation angles up to θGB = 24° was recorded even at 28 K, which is a required level for practical applications. Additionally, even in an applied magnetic field, θc was unaltered, and the decay of the intergrain Jc was small. Our results highlight the exceptional potential of Ba122:K for polycrystalline applications and pave the way for next-generation superconducting magnets.

In-situ high-temperature micromechanical behavior of flash-sintered strontium titanate

Strontium titanate (SrTiO3) is a versatile material with various applications but understanding its mechanical properties, especially in polycrystalline form prepared via field-assisted sintering methods, is limited. This study investigates the high-temperature mechanical properties of flash-sintered SrTiO3 through in-situ microcompression tests comparing the behaviors near the positive and negative electrodes. Due to a significant irregularity in densification, the negative electrode exhibited superior fracture strength and strain across all temperatures when compared to its positive counterpart. Micropillars near the positive electrode contained multiple pre-existing pores that became crack initiation sites, and thus inducing catastrophic failure. Micropillars near the negative electrode exhibited prominent intergranular cracks accompanied by high-density dislocations in the vicinity of the fracture surfaces. This study elucidates the effect of flash sintering-induced defects on the mechanical properties of polycrystalline SrTiO3 at various temperatures.

Harvesting of shear piezoelectricity in a molded multicomponent crystal disc

Biomolecular piezoelectrics, such as amino acids and peptides, exhibit significant shear piezoelectric responses in single crystal form. However, naturally occurring longitudinal piezoelectricity is rare and, when present, is dampened due to the multi-directional self-assembly in polycrystalline device layers. Here we utilise cocrystallisation to engineer a multicomponent crystalline salt hydrate of S(+)Mandelic Acid and LLysine, S-Mand•L-Lys•5H2O (1). This material exhibits a predicted single crystal longitudinal piezoelectric response of d33 = 3.5 pC/N. In polycrystalline form, 1 grows as an assembly of plates which increases the measured longitudinal piezoelectricity to 11 pC/N in its macroscopic solid-state. This is due to contributions from the shear piezoelectric response d36 = 10.8 pC/N, originating from the presence of plates oriented at acute angles relative to the surface. The brittleness of the crystals (E = 37 GPa) is overcome by reinforcing the substrate-free piezoelectric disc with a thin polymer coating to prevent flaking. Structural analysis confirms that the triclinic structure of 1 gives rise to this increased response due to the relative orientations of individual crystallites. Confined crystallisation of this multi-component form with a plate-like morphology, results in macroscopic self-assembly of an amino acid cocrystal that allows for the harvesting of higher shear piezoelectricity, but in a facile longitudinal configuration.

Robust Ferrimagnetism and Ferroelectricity in 2D ɛ-Fe2O3 Semiconductor with Ultrahigh Ordering Temperature.

2D single-phase multiferroic materials with the coexistence of electric and spin polarization offer a tantalizing potential for high-density multilevel data storage. One of the current limitations for application is the scarcity of the materials, especially those combine ferromagnetism and ferroelectricity at high temperatures. Here, robust ferrimagnetism and ferroelectricity in 2D ɛ-Fe2O3 samples with both single-crystalline and polycrystalline form are demonstrated. Interestingly, the polycrystalline nanosheets also exhibit easily switchable ferroelectric polarizations comparable to that of single crystals. The existence of grain boundary does not hinder the switching and retention of ferroelectric polarization. Furthermore, the ɛ-Fe2O3 nanosheets show ferrimagnetic and ferroelectric Curie temperatures up to 800K, which reaches record highs in 2D single-phase multiferroic materials. This work provides important progress in the exploration of 2D high-temperature single-phase multiferroics for potentially compact high-temperature information nanodevices.

Structural, magnetic, magnetocaloric behavior and magneto-transport, electrical polarization study in 3d based bulk and nano-crystalline multiferroic double perovskite Dy2MnCoO6

In this paper, we report a detailed investigation of the crystal structure, magnetic, magnetocaloric, magneto-transport and electrical polarization properties of a new multiferroic material in the polycrystalline and nanocrystalline form of the Dy2MnCoO6 double perovskite. Both compounds crystallized in the monoclinic structure with P21/n space group. The magnetic properties of both systems are mainly dominant ferromagnetic (FM) and weak antiferromagnetic (AFM). The FM/AFM coupling is related by the competing and combining functions of the radius and the magnetic moments of rare earth ions (i.e. 3d–4f exchange interactions). The reduction of the saturation magnetization in the isothermal magnetization curves can be explained by the existence of anti-phase boundaries and local anti-site defects in the system. Moreover, these materials hold reasonable values of magnetocaloric parameters and the absence of hysteresis makes the system a potential candidate for magnetic refrigeration. These compounds revealed two magnetic phase transitions, according to the appearance of two peaks in the temperature dependence of magnetic entropy change curves. The temperature dependent resistivity data for both the systems display semiconductor nature near room temperature and insulating like behavior at low temperature regime. The variable-range hopping conduction mechanism is used to best understand their transport mechanism. In addition, the electrical polarization loop at low temperature confirms the presence of ferroelectricity for both the studied systems. The decreases polarization under an external magnetic field evidence the weak magnetoelectric coupling. The coexistence of FM ordering with insulating behavior and ferroelectricity at low temperature promises new opportunities and improvements in next generation applications for information storage, spintronic, and sensors.

Computational homogenization of the elastic properties of polycrystalline fcc metals within Mindlin’s second strain-gradient theory

The lack of interest in Mindlin’s second strain-gradient theory, despite its success in characterizing various phenomena for which there is no explanation in the classical elasticity, is predominantly due to the numerous higher-order elastic constants involved therein. As an attempt to overcome this shortcoming, a computational homogenization method for determining such elastic constants of polycrystalline face-centered cubic (fcc) metals is proposed in the present study. In this homogenization method, using the Voigt-type averaging scheme, a polycrystalline material is modeled by an isotropic aggregate of randomly oriented single crystals without accounting for the grain size effect and the complexities due to grain boundaries and junctions. Subsequently, analytical expressions for the strain energy due to certain modes of loading are determined, and molecular simulations of a few fcc metals under such modes of loading are performed. Then, by fitting the corresponding analytical expressions to the results obtained from these simulations, the effective elastic constants and consequently the effective characteristic lengths of the fcc metals in their polycrystalline form are determined. Moreover, the free-surface-induced reconstruction in a thin layer of a solid is addressed both analytically and by molecular simulations, as a result of which the effective moduli of cohesion of the fcc metals in their polycrystalline form are calculated. In addition, the complete set of conditions for the positive-definiteness of the strain-energy-density function of isotropic materials within the adopted theory is derived, and subsequently a discussion of whether or not the numerical values obtained for the effective elastic moduli of the polycrystalline fcc metals satisfy such conditions is provided.

Tuning metastable austenite in a phase-transforming ceramic via matrix constraint

Martensitic phase-transforming ceramics can undergo reversible phase transformations under thermo-mechanical stimuli, yet brittle in their monolithic, polycrystalline form. Incorporating these ceramics into matrices thereby metastabilizing austenite gives rise to a significant toughening effect by triggering martensitic transformation. However, it remains a challenge to stabilize the austenite if the matrix is a light metal, because of its low strength, low melting temperature and high-chemical reactivity. In this study, we constructed a phase-transforming ceramic-metal (zirconia-aluminum) composite with tunable metastable austenite fractions via matrix constraint. Systematic experiments combined with thermodynamic and kinetic models uncover the effect of the matrix constraint and doping concentration on austenitization. By varying the processing parameters, we realized extensive tunability in metastable austenite content (0–100 wt.%) under different cerium doping concentrations (6–12 mol.%) in a wide range of processing temperatures (350–550°C). Our findings reveal the underlying mechanisms for promoting, stabilizing and fine-manipulating austenitization in martensitic phase-transforming ceramics under geometrical constraint, and may lay out the foundation for more extensive studies and applications of these phase-transforming ceramic-based composites.

High performance magnesium-based plastic semiconductors for flexible thermoelectrics

Low-cost thermoelectric materials with simultaneous high performance and superior plasticity at room temperature are urgently demanded due to the lack of ever-lasting power supply for flexible electronics. However, the inherent brittleness in conventional thermoelectric semiconductors and the inferior thermoelectric performance in plastic organics/inorganics severely limit such applications. Here, we report low-cost inorganic polycrystalline Mg3Sb0.5Bi1.498Te0.002, which demonstrates a remarkable combination of large strain (~ 43%) and high figure of merit zT (~ 0.72) at room temperature, surpassing both brittle Bi2(Te,Se)3 (strain ≤ 5%) and plastic Ag2(Te,Se,S) and organics (zT ≤ 0.4). By revealing the inherent high plasticity in Mg3Sb2 and Mg3Bi2, capable of sustaining over 30% compressive strain in polycrystalline form, and the remarkable deformability of single-crystalline Mg3Bi2 under bending, cutting, and twisting, we optimize the Bi contents in Mg3Sb2-xBix (x = 0 to 1) to simultaneously boost its room-temperature thermoelectric performance and plasticity. The exceptional plasticity of Mg3Sb2-xBix is further revealed to be brought by the presence of a dense dislocation network and the persistent Mg-Sb/Bi bonds during slipping. Leveraging its high plasticity and strength, polycrystalline Mg3Sb2-xBix can be easily processed into micro-scale dimensions. As a result, we successfully fabricate both in-plane and out-of-plane flexible Mg3Sb2-xBix thermoelectric modules, demonstrating promising power density. The inherent remarkable plasticity and high thermoelectric performance of Mg3Sb2-xBix hold the potential for significant advancements in flexible electronics and also inspire further exploration of plastic inorganic semiconductors.

Synthesis of New D-π-A Phenothiazine-Based Fluorescent Dyes: Aggregation Induced Emission and Antibacterial Activity.

Highly solid-state fluorescent dyes based on phenothiazine bearing sulfa-drug derivatives were successfully prepared and fully characterized by NMR, mass spectra, and elemental analysis. The prepared phenothiazine dyes bearing sulfadiazine and sulfathiazole 4-(((10-hexyl-10H-phenothiazin-3-yl)methylene)amino)-N-(pyrimidin-2yl) benzenesulfonamide (PTZ-1) and 4-(((10-hexyl-10H-phenothiazin-3-yl) methylene) amino)-N-(thiazol-2-yl)benzenesulfonamide (PTZ-2), showed strong emission in polycrystalline form, and significant emission in solution was observed. The quantum yield of the prepared dyes varied and decreased by increasing the solvent polarity, with the maximum recorded value being 0.63 and 0.6 in dioxane. Aggregation-induced emission (AIE) and the effect of the solvent polarity on absorption and emission spectra were investigated. The dyeing application of polyester fabrics using the prepared phenothiazine-based dyes was studied, showing very good affinity to dyed fabrics. The antibacterial affinity against gram-positive and gram-negative bacteria for the dye powder as well as the dyed PET fabric was investigated, with PTZ-2 showing better affinity against bacteria compared to PTZ-1. This multifunctional property highlights the potential uses of PTZ-1 and PTZ-2 for advanced applications in biomedicine and optoelectronics.

Magnetic anisotropy and associated entropy change in textured TmGa

Since Warburg's discovery of the magneto-caloric effect (MCE) in 1881, researchers have invested decades exploring its applications in the realm of magnetic cooling not only at room temperature but also at cryogenic temperatures. TmGa has emerged as a focus due to its notably high MCE performance. However, discrepancies have surfaced between the findings on single-crystalline TmGa reported by Gao et al. in 2013 and subsequent reports on polycrystalline TmGa. These disparities present significant challenges for ongoing TmGa research. To address these inconsistencies, this study prepares TmGa in a textured polycrystalline form. Magnetic measurements along both parallel (H∥a) and perpendicular (H⊥a) to the a-axis reveal pronounced magnetic anisotropy between the two directions. Notably, a distinct and complex anisotropic field-dependence in magnetic interaction and corresponding transitions are observed. Furthermore, magnetic entropy changes (∆Sm) for both H∥a and H⊥a, along with the corresponding anisotropic entropy change (∆Sman), are computed based on Maxwell’s relations. This investigation discloses maximum values of ∆Sman, reaching 17.2 J/kg K at T = 16.5 K and 24.3 J/kg K at T = 11.5 K for fields of 20 and 50 kOe, respectively, which are close to the largest value to date. These findings provide insights into fundamental magnetic properties and their potential applications for rotational magneto-caloric effects.

Formation of Fe4+ based on the Fe-O bond lengths in perovskite Eu1-xSrxFeO3

The physical properties of high oxidation state of transition metal oxide compounds have attracted many research interest for its potential applications. A systematic investigation of Fe4+ in Eu1-xSrxFeO3 with x = 0, 0.1, 0.2, 0.3, and 0.4 has been carried out in polycrystalline form obtained using sol-gel method. The single phase of Eu1-xSrxFeO3 is observed up to x = 0.3. The X-Ray powder pattern for low Sr content of x = 0.1, is best refined by using EuFeO3 crystal structure with Sr occupied the Eu-site. On the other hand, for higher Sr contents, two phases of EuFeO3 and Eu1/3Sr2/3FeO3 are required to obtained the best refinement. The result of the refinements shows that the volume and the average bond lengths of Fe-O decreases as increasing the Sr content. These results are consistent to support the existence of Fe4+ upon Sr doping in Eu1-xSrxFeO3. For the Sr content of x = 0.1, an anomalous change of the volume is observed.

Local Heating Induced Single-Crystalline Phase Control in Electrochemical Synthesis of Nanomaterials.

Development of synthetic strategies selectively yielding single crystals is desired owing to the facet-dependent chemical reactivities. Recent advances in electrochemical materials synthesis yielded nanomaterials that are surfactant-free, however, typically in polycrystalline forms. In this work, an electrochemical synthetic strategy selectively yielding single-crystalline nanoparticles by implementation of surface-selective heating of the working electrode is developed. Single crystals of copper, silver, gold, and platinum are afforded, and the crystallinity verified by electron diffraction and chemical reactivity studies. Notably, Cu (100) surface prepared by electrochemical synthesis yielded high single product selectivity when applied to electrochemical CO2 reduction catalysis.

A novel phosphate with CoII square planar coordination, BaCo0.5Fe(PO4)2: structural and magnetic features.

A novel phosphate containing barium, cobalt, and iron was synthesized in single-crystal and polycrystalline forms. Single crystal-based X-ray measurements revealed that it crystallizes in the monoclinic system with the P21/c space group. The structure is made up of linkages between FeO6 octahedra, CoO4 square planar units, CoO5 square pyramidal units, and PO4 tetrahedra through edges and/or vertices. The interconnection of these polyhedra leads to a three-dimensional framework with tunnels along the a-axis where the Ba2+ cations are located. The polycrystalline form was prepared via the sol-gel method and its XRD pattern was refined by the Le Bail method. Morphological and elemental mapping analyses of this phosphate were performed by scanning electron microscopy. In addition, infrared and Raman spectroscopy provided more insights into chemical bonding. The magnetic behavior was antiferromagnetic below TN ∼ 20 K. Optical measurements revealed a direct bandgap with an energy Eg of 2.83 eV.

Nitrate and nitroarene hydrogenations catalyzed by alkaline-earth nickel phosphide clathrates.

The alkaline-earth-containing nickel phosphide clathrates AeNi2P4 (Ae = Ba, Sr) are investigated as catalysts for the reduction of nitrate or nitroarenes in aqueous or ethanolic solution, respectively. While AeNi2P4 clathrates are inactive in their bulk polycrystalline form, they become active in nitrate hydrogenation after size reduction by either grinding or ball milling. However, while the clathrate structure remains intact after manual grinding, ball milling is of limited use as it results in significant clathrate degradation. Ground AeNi2P4 catalysts are also active in nitroarene hydrogenation. Condensation products such as azoxy- and azo-benzenes form early (4 h) but anilines accumulate after long reaction times (24 h). Unexpectedly, BaNi2P4 partially devinylates nitrostyrene to nitrobenzene. Overall, BaNi2P4 is more active than SrNi2P4 in both nitrate and nitroarene hydrogenation. These results showcase the potential utility of clathrates in a growing number of catalytic transformations.

Exploring the synthesis, structure, and optoelectronic properties of lead-free halide perovskite Cs3Bi2I9 in single crystal and polycrystalline forms

In recent years, caesium bismuth iodide (Cs3Bi2I9), a lead (Pb)-free halide perovskite, has drawn more attention as a potential material than traditional semiconductor materials due to its lack of Pb toxicity and its outstanding stability against atmospheric air and moisture. Herein, the inverse temperature crystallization method is adopted to grow high-quality hexagonal-phase Cs3Bi2I9 perovskite single crystals. Furthermore, a Cs3Bi2I9 perovskite thin film is fabricated by a solution process using the two-step spin coating technique. A collective analysis of the structural properties, surface morphology, thermal stability, phase transition, and optoelectronic properties of these single crystal and polycrystalline thin films provides a comprehensive understanding and design strategy to develop environmentally stable, Pb-free, and high-performance photovoltaic and optoelectronic devices based on Cs3Bi2I9 perovskite. The findings of this study contribute to the advancement of perovskite-based technologies and pave the way for their successful integration into the renewable energy and optoelectronics industries.

Crystallization heat treatments for the fabrication of volume Bragg gratings based on photo-thermo-refractive glass

Photo-thermo-refractive (PTR) glass is a functional optical material with broad applications in holographic optics. In this work, we examine the effect of crystallization heat treatment on the growth and distribution of sodium fluoride (NaF) nano-crystals in PTR glass using DSC, XRD, SEM, and TEM. The optical properties of the crystallized PTR glass are analyzed using a spectrophotometer. The results indicate that the NaF nano-crystals precipitated in PTR glass matrix are in the form of polycrystalline, and the growth of which is highly dependent on temperature. The growth of NaF nano-crystals saturates during the crystalline phase transition, resulting in decreased distribution uniformity. Higher crystallization temperature and longer crystallization time lead to an increase in absorption and scattering losses in the visible band. However, the crystallized PTR glass exhibits favorable absorption and scattering loss characteristics in the near-infrared band. By adjusting the crystallization treatments within the temperature range of 530 °C–570 °C for 10–120 min, refractive index modulation (RIM) values of the transmitting volume Bragg gratings (TVBG) ranging from 50 to 350 ppm can be achieved, which allows for maximum relative diffraction efficiencies exceeding 90% at 532 nm and 1053 nm using different crystallization processes. This research enhances the understanding of NaF nano-crystal growth mechanisms and provides insights into the application of holographic optical elements based on PTR glass in both the near-infrared and visible bands.