Aluminum Phosphate Glasses Research Articles

Sol-gel preparation of AlPO4–SiO2 glasses with high surface mesoporous structure

Transparent and colorless amorphous silica–aluminum phosphate gels and glasses along the composition line, xAlPO4–(1−x)SiO2 were prepared via the sol-gel route using tetraethylorthosilicate (TEOS), aluminum lactate, and ammonium dihydrogen phosphate as precursors. The glass-forming range was significantly extended, compared with that accessible by previously reported routes. After calcination at 600 °C, the amorphous AlPO4–SiO2 material exhibits an attractive mesoporous structure with surface areas as high as 582 m2 g−1. With increasing gel-processing and conversion temperature, the average degree of P/Al connectivity increases, while the Q3 silicon units present in the gels are gradually converted to Q4 units. After sample calcination above 600 °C for 8 h, the NMR results indicate that the structure of the prepared materials is composed of AlPO4- and SiO2-nanodomains.

Optical Properties of Potassium Aluminum Phosphate Glass Activated by Trivalent Titanium Ions

Potassium aluminum phosphate glass activated by trivalent Ti ions was obtained and investigated. Some physicochemical properties of the concentration series prepared, as well as the absorption and luminescence spectra at 293 K, were investigated. The data obtained are indicative of distorted octahedral coordination of Ti3+ ions. The optimal concentration interval for Ti3+ in the glass is proposed: 0.1–1 mol/l, in which the titanium concentration can be varied without violation of the physicotechnical and luminescence-kinetic properties of the glass. As a result, Ti3+ can be optimally used as an activator for phosphors on its basis. In addition, the sensitizing properties of Ti3+ can be used to excite other ions: Ho3+, Er3+, and Yb3+.

High-speed 1H MAS NMR investigations of the weathered surface of a phosphate glass

Solid-state high-speed 1H MAS NMR spectroscopy was used to investigate the weathered surface of a potassium aluminum phosphate (KAP) glass exposed to a humid environment (30K 2O 10Al 2O 3 60P 2O 5, mol%). Through the combination of spin–spin relaxation and double quantum (DQ) filtering it was possible to resolve seven or eight different proton environments within the weathered surface of the KAP glass. Two-dimensional (2D) DQ and 2D NOESY NMR correlation experiments were performed to probe the spatial proximity of these different proton species. These 1H– 1H correlation experiments helped confirm the spectral assignments. The analysis of these different 1H environments provides additional information about the chemical processes that occur at the weathered glass surface.

Sol–gel synthesis of Al2O3–P2O5glasses: mechanistic studies by solution and solid state NMR

Colorless and transparent aluminium phosphate gels and glasses with P/Al ratios ranging from 0.5 to 3.0 are prepared via the sol–gel process using aluminium lactate and phosphoric acid as precursors. This glass-forming range is significantly wider than accessible via the melt cooling route. Optimum pH ranges and thermal treatment conditions have been established on the basis of extensive solution- and solid state NMR spectroscopies. The NMR spectra help identify the various types of local environments present in the sols, gels and glasses, thereby providing a mechanistic understanding of the molecular transformation processes involved. Furthermore, they provide a basis for discussing the structural evolution as a function of composition. The formation of transparent gels and glasses is closely connected to high concentrations of the mixed [Al(lact)1(H2O)4]2+ and [Al(lact)2(H2O)2]+ complexes in the precursor solution. Addition of H3PO4 to such solutions results in multiple equilibria involving octahedrally coordinated aluminium complexes having variable lactate, phosphate and water ligands. The structure of the dried xerogels is dominated by the four octahedrally coordinated aluminium environments [Al(lact)3], [Al(lact)2(PO3)2]−, [Al(lact)1(PO3)4]2−, and [Al(PO3)6]3−, involved in various degrees of polymerization. Heat treatment of the dried xerogels at temperatures up to 400 °C results in further polymerization, producing AlO4, AlO5, and AlO6 coordination states. 27Al–31P double resonance experiments confirm that the extent of Al/P connectivity in the glasses is generally maximized. For those glasses that can be prepared by either sol–gel or melt-cooling procedures, all of the NMR experiments indicate virtually identical network structures for both preparation routes.

Waveguide fabrication in phosphate glasses using femtosecond laser pulses

We report on the response of glass to focused femtosecond (fs) laser pulses during waveguide fabrication in a commercial sodium aluminum phosphate glass (Schott IOG-1). Single-pass longitudinal translation of IOG-1 glass with respect to the focused laser beam at a rate of 20 μm/s and pulse energies of 3.5 μJ results in the formation of two waveguides located on opposite sides of the laser-exposed region, which itself does not guide light. This behavior is different from that of the more widely studied silica glass system. The precise location of the waveguides in IOG-1 glass depends on the relative tilt of the fs laser beam with respect to the sample translation direction. Fluorescence imaging of the modified glass using a confocal microscope setup reveals the formation of color center defects in the exposed region but not within the waveguides.

Structure and properties of lanthanum–aluminum–phosphate glasses

Glass-forming characteristics, properties and structural features of glasses in the La 2O 3–Al 2O 3–P 2O 5 system have been investigated. The glass-forming region is small compared to the Na 2O–Al 2O 3–P 2O 5 system. Glass transition temperature increases and thermal expansion coefficient, refractive index, and density all decrease as the alumina content of the glass is increased. Infrared (IR) spectroscopy indicates that the glass network is dominated by bridging P-tetrahedra with terminal tetrahedra present in glasses with O/P ratios >3. 27 Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy indicates that Al ions are incorporated in these glasses in 4-, 5-, and 6-coordinated sites. The average Al-coordination number (CN) increases with an increase in the Al/La ratio and decreases with an increase in the O/P ratio. Both trends can be explained by the avoidance of Al–O–Al bonds in the glass structure.

MOS capacitor properties passivated with aluminum phosphate glasses and effects of metal electrodes

MOS capacitor properties passivated with aluminum phosphate glasses and effects of metal electrodes

31P and 27Al MAS NMR investigations of some lead phosphate glasses

The 31P MAS NMR spectra were measured and analyzed for the two phosphate glasses that contain distinct metals (i.e., In or Ba), different amounts of PbO, and the same content of P 2O 5 and Al 2O 3. The 31P MAS NMR spectra for the two glasses have a single isotropic peak at −3.77 or −4.76 ppm, indicating that orthophosphate species are the dominant P sites in the glasses studied. The 27Al MAS NMR spectrum measured for the lead–barium–aluminum phosphate glass shows that the aluminum ions present in the glass are in 4-, 5-, and 6-fold coordination with oxygen and that the Al(OP) 4 is the dominant moiety for the glass, suggesting the formation of orthophosphate species in the glass.

Structural study of a lead–barium–aluminum phosphate glass by MAS-NMR spectroscopy

The 31 P - and 27 Al -MAS-NMR spectra of a lead–barium–aluminum phosphate glass were measured and analyzed, and the short range structure of the glass are discussed. The 31 P -MAS-NMR spectrum of the glass studied has a single isotropic peak at −4.76 ppm, indicating that orthophosphate species are the dominant P-sites in the glass. The 27 Al -MAS-NMR spectrum of the glass shows that the aluminum ions present in the glass are in 4-, 5-, and 6- fold coordination with oxygen, and that the Al(OP) 4 is the dominant moiety for the glass, suggesting the formation of orthophosphate species in the glass.

Optical and acousto-optical properties of Nd:phosphate glasses

Nd 3+-doped potassium barium aluminum phosphate (KBAP) glasses have been synthesized with a Nd concentration of 4%. The glasses are characterized for their optical and acousto-optical properties and these properties are compared with fused quartz and LiNbO 3. The refractive index of this glass varies from 1.976 to 1.523 in the wavelength range 200–2500 nm, with a value of 1.612 at 633 nm. The acoustic velocity and the photoelastic constant are 7.31 × 10 5 cm/s and 0.226 respectively. Acousto-optic figures of merit of this material are comparable to those of quartz. It has been concluded that these glasses can be effectively used at high frequencies for wideband acousto-optic deflector and modulator applications.

Nuclear magnetic resonance study of a high-surface-area aluminum phosphate glass and its thermally reversible sol-gel precursor

A novel reaction, based on sol-gel chemistry using an aluminum alkoxide and phosphoric acid to produce a high-surface-area aluminum phosphate glass, was followed by 27Al and 31P nuclear magnetic resonance (NMR). The gelled portion of the alcoholic solutions could be characterized with solid state 27Al methods. We discovered that the gelation, which is very rapid under normal conditions, can be controlled by the addition of HCl to the solution and that the gelation is thermally reversible in the presence of HCl. The NMR results showed that this modified sol-gel behavior is a result of acid hydrolysis of the AlP bonds, leading to network termination by POH groups and octahedrally solvated Al atoms. Similar local structures persist in the amorphous calcination product. The glass surface contains Al sites with strong quadrupole interaction. These sites could not be detected by conventional 27Al NMR methods but their existence was demonstrated with a static echo experiment. The quadrupole coupling constant was determined with the recently introduced transfer of populations in double resonance (TRAPDOR) method (a sol 1H 27Al double resonance magic-angle spinning experiment). The TRAPDOR results also showed that these sites, which constitute about 30% of the Al in the glass, carry hydroxyl groups. Characterization of the atomic structure of high-surface AlPO 4 is important for its use as catalyst support.

Preparation and thermal properties of a leadindiumaluminum phosphate glass

A wet chemical process has been developed for the preparation of a leadindium phosphate compound, and the effect of incorporation of aluminum into the compound on the thermal properties of the resulting glass is reported. High field 27Al NMR in combination with a magic angle spinning technique was used to investigate the aluminum coordination in the leadindiumaluminum phosphate glass. The transition, crystallization and softening temperatures and thermal expansion coefficient of the glass were determined by means of DTA, TMA and dilatometric measurements.

Neodymium-chromium doped phosphate glasses as luminescent solar concentrators

A luminescent solar concentrator based on Nd 3+ and Cr 3+ doubly doped lithium aluminium phosphate glass for solar energy conversion applications has been presented. Absorption and fluorescence spectra and quantum yield of lithium aluminium phosphate glasses are reported. The dependence of the light concentration coefficient versus dopant concentration and attenuation of the guided light in the luminescent solar concentrator have been studied. The best results were obtained for glass doped with 0.07 × 10 20 ions/cm 3 of Cr 3+ and 6.97 × 10 20 ions/cm 3 of Nd 3+. In addition, technology and properties of silicon solar cells operating with luminescent solar concentrators have been briefly outlined.

Decomposition of broad absorption band at about 3·2 μm in multicomponent aluminophosphate glasses

The decomposition of the broad absorption band at about 3·2 μm in multicomponent aluminiumphosphate glasses was made using a computer Tesla 200. The results show that the band is composed of at least three bands. It is suggested that the two side bands are due to the stretching vibrations of the residual water molecules in the glass and only the middle band belongs to the protons.

Radiation dosimeters based on thermoluminescence measurements in aluminum phosphate glass (IKS dosimeters)

Glass dosimeters useful in beta-gamma dosimetry, slow neutron dosimetry, and the dosimetry of high-energy charged particles in the 0.02 to (1–2)·106 rad range have been developed. The dosimeters are capable of storing and retaining information for an unusually long interval (as long as a month in a 150°C environment). These glasses are not excited by daylight, but daylight does exert a deexcitation effect: 26 to 38% of the stored light sum is dissipated by deexcitation in a period of 40 days.