Gallium Phosphate Research Articles

The Influence of Pressure on the Electronic and Elastic Characteristics of GaP Nanocrystals using Density Functional Theory

The electronic structural and mechanical properties of III-V Gallium Phosphide (GaP) nano-crystals zinc-blende stable (ZB) phase under pressure dependence have been studied via the model of the density functional theory (DFT) in combination with the large unit cell (LUC) approach at (8, 16, 54 & 64) atoms. The exchanges and correlations (XC) energy has been defined in all approaches through generalized gradient approximations of the Perdew-Burke-Ernzerhof (GGA-PBE), and determination of GaP characteristics in the case where the pressure has been increased from 0GPa to ±50GPa. Elastic parameters like elastic constants (C11, C12 & C44), Kleinmann parameter (ξ), Zener anisotropic factor (A), shear modulus (G), Young's modulus (E), Poisson’s ratio (v), Bulk modules (B) of GaP-ZB structure have been calculated and showed systematic variation with a pressure increase. Our calculations show that Bulk modules and sound speed increase with an increase in the number of core atoms. In this systematic approach, it has been found that the B/G ratio is 1.58 for this compound and it exhibits a negative Cauchy pressure, classifying GaP as brittle. The results were discovered to be consistent with other theoretical as well as experimental results. The present study directly relates to the latest experimental works on the III-phosphide compounds. The current results provide information and direction for further investigation into the fundamentals and potential applications of gallium phosphate (GaP) nanocrystals. In addition, we attempted to compare the results of the investigation with some similar types of compounds that are already documented in the literature. We believe that our study will have a significant impact on both the field of research and contemporary technology based on semi-conducting materials.

Cross-Validation of the Remarkably High Surface Oxygen Exchange Kinetics of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ: A Combined Thin-Film Mass Relaxation and Bulk Electrical Conductivity Relaxation Study.

In this work, we measure the oxygen kinetic properties of double perovskite PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), a material widely used as the air electrode in solid oxide electrochemical cells, by mass relaxation (MR) and electrical conductivity relaxation (ECR) experiments. MR studies are carried out using thin films deposited on a gallium phosphate piezocrystal microbalance, and ECR studies are performed using a bulk bar sample with 97% theoretical density. Measurements are performed at 600 °C over the temperature oxygen partial pressure range from 10-4 to 0.21 atm. Despite the differences in experimental formats and surface microstructural features, the ks values extracted from the two methods are found to be in good agreement with one another. The rate constant is found to increase with oxygen partial pressure with a power law dependence, rising from 1.0 × 10-6 cm/s at 3.2 × 10-4 atm to 1.2 × 10-4 cm/s at 0.24 atm, as averaged over the oxidation and reduction directions. The rates in the oxidation direction are observed to be slightly higher than those in the reduction direction for a given pair of pO2 values, suggesting that the final pO2 value controls the overall relaxation behavior. The power law exponent describing the dependence of ks on pO2 is found to be 0.74 ± 0.01. The ECR study of the bulk sample reveals that even with a diffusion length of 1.8 mm, the relaxation process is largely free of diffusion limitations, indicating that PBSCF has the high bulk transport properties required for a double-phase boundary oxidation/reduction pathway.

Absorption coefficients and scattering losses of TGG, TGP, KTF, FS, and CeF3 magneto-optical crystals in the visible via cavity ring-down spectroscopy.

We demonstrate a method for determining small absorption coefficients and surface-scattering losses of crystals using cavity ring-down spectroscopy and perform measurements on magneto-optical crystals of terbium gallium garnet (TGG), terbium gallium phosphate (TGP), fused silica (FS), potassium terbium fluoride (KTF), and C e F 3 at 532 and 634nm. Surface scattering is distinguished from absorption losses by using crystals of different lengths. A figure of merit (FoM) for magneto-optical crystals is defined to evaluate their suitability as intracavity optics in optical cavity applications. It is found that TGP has the highest FoM for crystal lengths up to ∼10m m, whereas C e F 3 and FS potentially outperform TGP for longer crystals. Single-pass applications are also briefly discussed.

Persistent luminescent phosphor-in-glass composites based on NaPO3 – Ga2O3 glasses loaded with Sr2MgSi2O7:Eu2+,Dy3+

Phosphor-in-glass (PiG) is a composite material that can combine the chemical stability and more versatile molding and processing of glasses and the singular properties of luminescent polycrystalline materials. Persistent luminescent phosphors have been raising attention due to their long emission times without the need for a steady irradiation source. The association of these polycrystalline materials with transparent glassy hosts leads to the obtainment of robust luminescent bulk materials and expands the possibilities of commercial applications. In this work, the Sr2MgSi2O7:Eu2+,Dy3+ (SMSO) persistent luminescent material was incorporated into a new gallium phosphate glass system with composition 80NaPO3 – 20Ga2O (NaPGa), through the conventional melt-quenching technique and fully characterized from the structural and spectroscopic viewpoints. The composites were prepared using 2, 5, 10, and 20 wt% of SMSO at 900 or 950 °C. It was observed that the higher melting temperature induces the oxidation of Eu2+ ions, which can reduce the persistent luminescent emission. High SMSO concentrations increase the glass melt viscosity, hampering the molding step but optimized samples were successfully obtained as transparent bulk materials with efficient emission in the blue spectral region and promising applications in emergency signaling and as solar cell sensitizers.

Time-resolved structure analysis of vibrating gallium phosphate under alternating electric field

Time-resolved structure analysis of vibrating gallium phosphate under alternating electric field

High Temperature Ultrasonic Transducers: A Review.

There are many fields such as online monitoring of manufacturing processes, non-destructive testing in nuclear plants, or corrosion rate monitoring techniques of steel pipes in which measurements must be performed at elevated temperatures. For that high temperature ultrasonic transducers are necessary. In the presented paper, a literature review on the main types of such transducers, piezoelectric materials, backings, and the bonding techniques of transducers elements suitable for high temperatures, is presented. In this review, the main focus is on ultrasonic transducers with piezoelectric elements suitable for operation at temperatures higher than of the most commercially available transducers, i.e., 150 °C. The main types of the ultrasonic transducers that are discussed are the transducers with thin protectors, which may serve as matching layers, transducers with high temperature delay lines, wedges, and waveguide type transducers. The piezoelectric materials suitable for high temperature applications such as aluminum nitride, lithium niobate, gallium orthophosphate, bismuth titanate, oxyborate crystals, lead metaniobate, and other piezoceramics are analyzed. Bonding techniques used for joining of the transducer elements such as joining with glue, soldering, brazing, dry contact, and diffusion bonding are discussed. Special attention is paid to efficient diffusion and thermo-sonic diffusion bonding techniques. Various types of backings necessary for improving a bandwidth and to obtain a short pulse response are described.

Synthesis, crystal structures and optical properties of open-framework gallium phosphates: NaGa3F4(PO4)2(H2O)2 and AGa2P2O7(OH)3(H2O) (A = K, Rb)

Three new alkali-metal gallium phosphates NaGa3(PO4)2F4(H2O)2 (1), KGa2P2O7(OH)3(H2O) (2), and RbGa2P2O7(OH)3(H2O) (3) were obtained using hydrothermal methods. Compound 1 crystallizes in the chiral space group P43212. The structure of 1 features a three-dimensional (3D) framework composed of 2D layers of corner-sharing GaO4F2 and GaO2F4 octahedra that are further bridged by PO4 tetrahedra with Na+ cations residing in the oxyfluorinated gallolayers. Compounds 2 and 3 are isostructural, both crystallizing in the centrosymmetric space group P21/c; their structures consist of novel 3D gallophosphate frameworks constructed from Ga4O20 tetramers interconnected by PO4 units with 8-membered ring channels along the b-axis, in which K+/Rb+ cations are located. The diffuse reflectance spectra show that the ultraviolet (UV) cut-off edges are about 292 ​nm (4.25 ​eV), 275 ​nm (4.51 ​eV) and 306 ​nm (4.05 ​eV) for 1–3, respectively. Luminescent studies suggest that 1–3 emit blue light under the excitation of near-ultraviolet light.

High-temperature oxidation evaluation using crystal microbalance

ABSTRACT High-temperature oxidising environments are frequently encountered but the limited number of in situ techniques that can be implemented has hindered the monitoring possibilities and a better comprehension of the oxidation phenomenon. In this paper, the high-temperature oxidation behaviours of three alloys (AISI 316L, AISI 310 and HAYNES® HR-120®) were studied by using crystal microbalances. Two types of crystal were tested: quartz or gallium orthophosphate crystals. First the behaviour of thin sputtered deposited alloys on quartz slides was studied at 400 and 700°C under air oxidising conditions and compared to bulk samples. Kinetics measurements were performed on the three alloy films deposited on the resonators at 400 or 700°C: it was possible to measure very small mass variations associated with thin oxide formation between 5 and 180 nm of thickness. The crystal microbalance technique gives promising perspectives in understanding the high-temperature corrosion and scaling mechanisms and also for in situ monitoring.

Gallium phosphate glass (GPG)를 첨가한 글라스아이오노머 시멘트의 기계적 성질과 항균효과

Gallium phosphate glass (GPG)를 첨가한 글라스아이오노머 시멘트의 기계적 성질과 항균효과

Development of Ultrasonic Guided Wave Transducer for Monitoring of High Temperature Pipelines.

High-temperature (HT) ultrasonic transducers are of increasing interest for structural health monitoring (SHM) of structures operating in harsh environments. This article focuses on the development of an HT piezoelectric wafer active sensor (HT-PWAS) for SHM of HT pipelines using ultrasonic guided waves. The PWAS was fabricated using Y-cut gallium phosphate (GaPO4) to produce a torsional guided wave mode on pipes operating at temperatures up to 600 °C. A number of confidence-building tests on the PWAS were carried out. HT electromechanical impedance (EMI) spectroscopy was performed to characterise piezoelectric properties at elevated temperatures and over long periods of time (>1000 h). Laser Doppler vibrometry (LDV) was used to verify the modes of vibration. A finite element model of GaPO4 PWAS was developed to model the electromechanical behaviour of the PWAS and the effect of increasing temperatures, and it was validated using EMI and LDV experimental data. This study demonstrates the application of GaPO4 for guided-wave SHM of pipelines and presents a model that can be used to evaluate different transducer designs for HT applications.

Charge Separation Enhancement Mechanism By p-n Junction in Water Reduction Electrode

Solar water splitting overall efficiency largely depends on the photoanode/photocathode charge carrier separation efficiency. Understanding the competition between charge separation and charge recombination is crucial to improve the device efficiency. In this study first we discussed the challenges in studying such process with femtosecond transient spectroscopy. Then we demonstrated a feasible method by combining transient reflectance (TR) spectroscopy and in situ electrochemical measurement to provide critical information on charge carrier separation efficiency and IPCE on a water/CO2 reduction photoanode, p-type gallium phosphate with protective titanium dioxide (TiO2) layer. Enhanced charge separation at the interface of gallium phosphate (GaP, 100) single crystal and TiO2 layer is observed by TR. The separated charge carrier concentration obtained by reflectance change shows strong correlation to the IPCE measured in situ under same condition. Through this correlation we provided direct evidence that the IPCE is heavily determined by the transiently separated charge carriers. This study also provides an applicable and powerful method to study similar HER and OER semiconductor electrode photogenerated charge carrier dynamics at ultrafast time scale.

An atomically thin molecular aperture: two-dimensional gallium phosphate

Stretching two-dimensional GaPO4 causes its GaO4 and PO4 building blocks to counter-rotate allowing its pore size to be dynamically tuned to allow specific molecules to pass through.

Effects of Gamma Radiation on Resonant and Antiresonant Characteristics of Piezoelectric Wafer Active Sensors

This paper presents gamma radiation effects on resonant and antiresonant characteristics of piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM) applications to nuclear-spent fuel storage facilities. The irradiation test was done in a Co-60 gamma irradiator. Lead zirconate titanate (PZT) and Gallium Orthophosphate (GaPO4) PWAS transducers were exposed to 225 kGy gamma radiation dose. First, 2 kGy of total radiation dose was achieved with slower radiation rate at 0.1 kGy/h for 20; h then the remaining radiation dose was achieved with accelerated radiation rate at 1.233 kGy/h for 192 h. The total cumulative radiation dose of 225 kGy is equivalent to 256 years of operation in nuclear-spent fuel storage facilities. Electro-mechanical impedance and admittance (EMIA) signatures were measured after each gamma radiation exposure. Radiation-dependent logarithmic sensitivity of PZT-PWAS in-plane and thickness modes resonance frequency (∂(fR)/∂( logeRd)) was estimated as 0.244 kHz and 7.44 kHz, respectively; the logarithmic sensitivity of GaPO4-PWAS in-plane and thickness modes resonance frequency was estimated as 0.0629 kHz and 2.454 kHz, respectively. Therefore, GaPO4-PWAS EMIA spectra show more gamma radiation endurance than PZT-PWAS. Scanning electron microscope (SEM) and X-ray diffraction method (XRD) was used to investigate the microstructure and crystal structure of PWAS transducers. From SEM and XRD results, it can be inferred that there is no significant variation in the morphology, the crystal structure, and grain size before and after the irradiation exposure.

Printing two-dimensional gallium phosphate out of liquid metal

Two-dimensional piezotronics will benefit from the emergence of new crystals featuring high piezoelectric coefficients. Gallium phosphate (GaPO4) is an archetypal piezoelectric material, which does not naturally crystallise in a stratified structure and hence cannot be exfoliated using conventional methods. Here, we report a low-temperature liquid metal-based two-dimensional printing and synthesis strategy to achieve this goal. We exfoliate and surface print the interfacial oxide layer of liquid gallium, followed by a vapour phase reaction. The method offers access to large-area, wide bandgap two-dimensional (2D) GaPO4 nanosheets of unit cell thickness, while featuring lateral dimensions reaching centimetres. The unit cell thick nanosheets present a large effective out-of-plane piezoelectric coefficient of 7.5 ± 0.8 pm V−1. The developed printing process is also suitable for the synthesis of free standing GaPO4 nanosheets. The low temperature synthesis method is compatible with a variety of electronic device fabrication procedures, providing a route for the development of future 2D piezoelectric materials.

The ionothermal synthesis and properties of new gallium phosphates substituted by Co and Fe

Two microporous gallium phosphates substituted by Fe and Co: NH4[Ga2Fe(PO4)3(H2O)2] (1) and NH4[Ga2Co(PO4)3(H2O)2] (2) have been ionothermally synthesized by using the ionic liquid [Bmim]Br as structure-directing agent and solvent. X-ray single crystal diffractions show that 1 and 2 are isostructural and possess 3D channel filled by ammonium groups. The morphologies of compounds 1 and 2 are characterized by scanning electron micrographs (SEM). Effects of P2O5/Ga2O3 ratio on the crystallization of compound 2 are investigated. The optimal synthesis condition with the molar composition of Ga2O3:6P2O5:3.6HF:3Co salt:40[Bmim]Br is determined, and X-ray powder diffraction indicates that the compound 2 is pure crystalline phase under the optimal conditions. The thermogravimetric analysis shows that the framework of 2 collapses at temperatures above 460 °C. Compound 2 exhibits antiferromagnetic property by magnetic test.

Efficient excitation and amplification of the surface plasmons

One dimensional (1D) grating has been fabricated (using focused ion beam) on 50 nm gold (Au) film deposited on higher refractive index Gallium phosphate (GaP) substrate. The sub-wavelength periodic metal nano structuring enable to couple photon to couple with the surface plasmons (SPs) excited by them. These grating devices provide the efficient control on the SPs which propagate on the interface of noble metal and dielectric whose frequency is dependent on the bulk electron plasma frequency of the metal. For a fixed periodicity (Λ = 700 nm) and slit width (w = 100 nm) in the grating device, the efficiency of SPP excitation is about 40% compared to the transmission in the near-field. Efficient coupling of SPs with photon in dielectric provide field localisation on sub-wavelength scale which is needed in Heat Assisted Magnetic recording (HAMR) systems. The GaP is also used to emulate Vertical Cavity Surface emitting laser (VCSEL) in order to provide cheaper alternative of light source being used in HAMR technology. In order to understand the underlying physics, far-and near-field results has been compared with the modelling results which are obtained using COMSOL RF module.Apart from this, grating devices of smaller periodicity (Λ = 280 nm) and slit width (w = 22 nm) has been fabricated on GaP substrate which is photoluminescence material to observe amplified spontaneous emission of the SPs at wavelength of 805 nm when the grating device was excited with 532 nm laser light. This observation is unique and can have direct application in light emitting diodes (LEDs).

Exploring the possibility of GaPNTs as new materials for hydrogen storage

The possibility of hydrogen storage in gallium phosphate nanotubes (GaPNTs) as a high-capacity hydrogen storage media is studied by employing ab-initio density functional theory (DFT) calculations with a van der Waals (VdW) correction. The binding energy, the distance of the adsorbed hydrogen molecules and the charge transfer were particularly calculated. The obtained results indicate that hydrogenation of the GaPNTs is sensitive to the curvatures and chiralities of the nanotubes. It is found that the binding energy of hydrogen physisorption on GaP nanotubes is higher that on carbon nanotubes. These results are useful in the search for a proper media for hydrogen storage at ambient conditions.

Structural Characterization of Novel Cerium Phosphate Glass Ionomer Cements (GICs) Doped with GaCl (Phthalocyanine)

Cerium Pyrophosphate glass is prepared and investigated by different structural techniques. Resin modified glass ionomer cements (RGICs) of pyro cerium phosphate (40CeO2-60P2Os) composition doped with different concentrations from GaCl Phthalocyanine (C32H16ClGaN8) have been also prepared and studied for the first time. Different techniques have been applied to shed light on the structural changes induced upon addition of GaCl-Phthalocyanine. The corresponding changes in material structure are widely approved by results of 31P magic angle spinning nuclear magnetic resonance (MAS-NMR), X-Ray diffraction and FTIR spectroscopy. The network structure of both base glass and GIC free from C32H16ClGaN8 is confirmed to be amorphous. Doping even with little concentration from GaCl-Phthalocyanine leads to changing the network structure from amorphous to a highly crystalline one. Formulation of GaCl-Phthalocyanine with water soluble acid leads to monocrystalline structure due to monoclinic lattice structure of Phthalocyanine. Carbonated hydroxyl cerium and gallium phosphate structural phases are evidenced to be formed upon GaCl-Phthalocyanine addition. Presence of such bioactive phases can support that the prepared GICs of considerable C32H16ClGaN8 concentration (1 and 1.5 mol%) can be applied as biocompatible materials used in biodental applications. The morphologies of some selected samples were characterized by SEM. The micrographs have revealed that formulating of cerium phosphate powder of the amorphous glass with polymeric acid successfully led to the formation of CePO4-H2O nanofibrous bundles. But formulation with GIC containing GaCl-Phthalocyanine can simply form co-aligned and elongated nanofibers (15 - 40 nm thick and up to ca. 1.2 m long). The formed nanofibers are mainly consisted of hydrated and carbonated CePO4 and GaPO4 nanocrystals. The hardness of the cemented material increases with increasing GaCl-Phthalocyanine concentrations.

A radioluminescent nuclear battery using volumetric configuration: 63Ni solution/ZnS:Cu,Al/InGaP

Energy dense power sources are critical to the development of compact, remote sensors for terrestrial and space applications. Nuclear batteries using β--emitting radioisotopes possess energy densities 1000 times greater than chemical batteries. Their power generation is a function of β- flux saturation point relative to the planar (2D) configuration, β- range, and semiconductor converter. An approach to increase power density in a beta-photovoltaic (β-PV) nuclear battery is described. By using volumetric (3D) configuration, the radioisotope, nickel-63 (63Ni) in a chloride solution was integrated in a phosphor film (ZnS:Cu,Al) where the β- energy is converted into optical energy. The optical energy was converted to electrical energy via an indium gallium phosphate (InGaP) photovoltaic (PV) cell, which was optimized for low light illumination and closely matched to radioluminescence (RL) spectrum. With 15mCi of 63Ni activity, the 3D configuration energy values surpassed 2D configuration results. The highest total power conversion efficiency (ηt) of 3D configuration was 0.289% at 200µm compared 0.0638% for 2D configuration at 50µm. The highest electrical power and ηt for the 3D configuration were 3.35 nWe/cm2 at an activity of 30mCi and 0.289% at an activity of 15mCi, respectively. By using 3D configuration, the interaction space between the radioisotope source and scintillation material increased, allowing for significant electrical energy output, relative to the 2D configuration. These initial results represent a first step to increase nuclear battery power density from microwatts to milliwatts per 1000cm3 with the implementation of higher energy β- sources.

Experimental and first-principles calculation study of the pressure-induced transitions to a metastable phase inGaPO4and in the solid solutionAlPO4−GaPO4

$\ensuremath{\alpha}$-Quartz-type gallium phosphate and representative compositions in the $\mathrm{AlP}{\mathrm{O}}_{4}\text{\ensuremath{-}}\mathrm{GaP}{\mathrm{O}}_{4}$ solid solution were studied by x-ray powder diffraction and absorption spectroscopy, Raman scattering, and by first-principles calculations up to pressures of close to 30 GPa. A phase transition to a metastable orthorhombic high-pressure phase along with some of the stable orthorhombic $Cmcm\mathrm{CrV}{\mathrm{O}}_{4}$-type material is found to occur beginning at 9 GPa at $320{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ in $\mathrm{GaP}{\mathrm{O}}_{4}$. In the case of the $\mathrm{AlP}{\mathrm{O}}_{4}\text{\ensuremath{-}}\mathrm{GaP}{\mathrm{O}}_{4}$ solid solution at room temperature, only the metastable orthorhombic phase was obtained above 10 GPa. The possible crystal structures of the high-pressure forms of $\mathrm{GaP}{\mathrm{O}}_{4}$ were predicted from first-principles calculations and the evolutionary algorithm USPEX. A predicted orthorhombic structure with a $Pmn{2}_{1}$ space group with the gallium in sixfold and phosphorus in fourfold coordination was found to be in the best agreement with the combined experimental data from x-ray diffraction and absorption and Raman spectroscopy. This method is found to very powerful to better understand competition between different phase transition pathways at high pressure.