Search

The purpose of this study was to evaluate the effects of different production techniques on the optical properties of the zirconia-reinforced lithium silicate ceramics.

Nd3+doped La2Ti2O7, Ce4+doped Sm2Ti2O7and Gd3+doped Er2Ti2O7have been synthesized at different reaction temperatures using solid state reaction method, and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TG). Excitation spectra, emission spectra and decay time curves of the samples were investigated by photoluminescence spectrophotometer (PL) and typical transitions of rare earth ions were observed. Dielectric properties, piezoelectric properties and Curie temperature of the obtained luminescent materials were measured for electrical characterization. The results showed that all materials have both photoluminescent and piezoelectric properties and show high Curie temperature.

In this study, silicate systems, M2SiO4(M = Ca, Zn) were produced by solid state reaction and doped with 1 mol% Eu3+rare-earth ion. Their heat treatments, which were conducted at 1200 °C and above for minimum 3 hours under an open atmosphere, were applied according to the DTA/TG results. Powder X-ray diffraction XRD analyses were performed to determine the phase properties of the phosphor systems after the sintering process. It was proved that the structures of two of the phosphor systems were well formed in except that the Zn2SiO4had some ZnO secondary phases. The expected photoluminescence (PL) results were presented and the transitions of the Eu3+ions were observed for both phosphors.

A horizontal linear heat flow apparatus connected to an optical microscope was used to directly observe the grain boundary groove shapes of solid neopentylglycol solution equilibrated with neopentylglycol-succinonitrile eutectic liquid at a constant temperature gradient. The thermal conductivity variations with temperaure for solid neopentylglycol solution and neopentylglycol-succinonitrile eutectic solid were measured with a radial heat flow apparatus. By using the observed grain boundary groove shapes and measured values of temperature gradients and thermal conductivity of solid phase and liquid phase, the values of the Gibbs–Thomson coefficient, solid–liquid interfacial energy and grain boundary energy were determined for the solid neopentylglycol solution equilibrated with the neopentylglycol-succinonitrile eutectic liquid.

The silicate-type and Eu3+-activated Sr3SiO5and Mg3SiO5were prepared through the high temperature solid state reaction method under an open atmosphere. DTA/TG analysis was conducted to obtain information about the thermal behaviors of the mixed reactants. Using the DTA/TG results, the sintering process was achieved and the phase properties were characterized by X-ray diffraction (XRD). The effects of the same activator (Eu3+) and co-dopant (Dy3+) on the photoluminescence (PL) properties of the host lattices were investigated by using a photoluminescence spectrometer.

In this work, aluminate type phosphorescence materials were synthesized via the solid state reaction method and the photoluminescence (PL) properties, including excitation and emission bands, were investigated considering the effect of trace amounts of activator (Eu3+) and co-activator (Dy3+). The estimated thermal behavior of the samples at certain temperatures (> 1000 °C) during heat treatment was characterized by differential thermal analysis (DTA) and thermogravimetry (TG). The possible phase formation was characterized by X-ray diffraction (XRD). The morphological characterization of the samples was performed by scanning electron microscopy (SEM). The PL analysis of three samples showed maximum emission bands at around 610 nm, and additionally near 589 nm, 648 nm and 695 nm. The bands were attributed to typical transitions of the Eu3+ions.

Mn4+ doped and Pr3+,4+, Sm3+, Gd3+, Tb3+,4+, Ho3+, Er3+, Tm3+ and Yb3+ co-doped MgAl2Si2O8-based phosphors were prepared by conventional solid state synthesis at 1300 °C. They were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray powder diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM). The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600-715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the intrinsic 2E→4A2 transitions of Mn4+.

The Akermanite type alkaline earth silicate Ca2MgSi2O7 activated by different types of rare earths was prepared by the conventional solid state reaction method under weak reductive atmosphere. The phase formation, particle size distribution, particle morphologies and photoluminescence properties of the samples have been investigated respectively. The comparative results of SEM and laser particle size analysis revealed that the relatively regular morphology, smaller particle size distribution could be achieved for the phosphors synthesized by the solid state reaction method including dry-ground after which powders were sieved below 170 meshes. The effects of rare earth oxides; Nd2O3, Pr6O11, Ce2O3 and Sm2O3 on the luminescence properties of the host material, Ca2MgSi2O7, were studied. Remarkable enhancement and novel color emitting including white in luminescence characteristics of host material were observed as a result of doping the mentioned rare-earths were doped.

ABSTRACTLike many algae, Chlamydomonas reinhardtiiis phototactic, using two anterior flagella to swim toward light optimal for photosynthesis. The flagella are responsive to signals initiated at the photosensory eyespot, which comprises photoreceptors in the plasma membrane and layers of pigment granules in the chloroplast. Phototaxis depends on placement of the eyespot at a specific asymmetric location relative to the flagella, basal bodies, and bundles of two or four highly acetylated microtubules, termed rootlets, which extend from the basal bodies toward the posterior of the cell. Previous work has shown that the eyespot is disassembled prior to cell division, and new eyespots are assembled in daughter cells adjacent to the nascent four-membered rootlet associated with the daughter basal body (D4), but the chronology of these assembly events has not been determined. Here we use immunofluorescence microscopy to follow assembly and acetylation of the D4 rootlet, localization of individual eyespot components in the plasma membrane or chloroplast envelope, and flagellar emergence during and immediately following cell division. We find that the D4 rootlet is assembled before the initiation of eyespot assembly, which occurs within the same time frame as rootlet acetylation and flagellar outgrowth. Photoreceptors in the plasma membrane are correctly localized in eyespot mutant cells lacking pigment granule layers, and chloroplast components of the eyespot assemble in mutant cells in which photoreceptor localization is retarded. The data suggest that plasma membrane and chloroplast components of the eyespot are independently responsive to a cytoskeletal positioning cue.

In this study, after doping Tb4O7to α-Bi2O3in the range of 1% ≤ n≤ 50% in a series of different mol ratios, heat treatment was carried out by applying cascade temperature rise in the range of 600°C–950°C for 72 hours, and new phases were obtained in Bi2O3–Tb4O7system. After 72 hours of heat treatment at 800°C, 1% and 2% mol of Tb4O7-containing mixtures formed tetragonal phase; 6%, 13%–20% and 30% mol of Tb4O7-containing mixtures formed face-centered cubic phase; 7%–10%, 15% and 18% mol of Tb4O7-containing mixtures were put in quenching process at 750°C and face-centered cubic phases were obtained. Similarly, 1% and 3%–5% mol of Tb4O7-containing mixtures formed a tetragonal phase. With the help of x-ray diffraction, crystal systems and lattice parameters of solid solutions were obtained and their characterization was carried out. Their surface and particle properties were detected and microprobe analysis was performed by scanning electron microscope.

In this study, after doping ytterbium oxide (Yb2O3) to α-bismuth trioxide (α-Bi2O3) in the range of 9% ≤ n≤ 20% in a series of different mole ratios, heat treatment was performed by applying a cascade temperature rise in the range of 700–790°C for 48 hours and new phases were obtained in the (Bi2O3)1 − x(Yb2O3)xsystem. After 24 hours of heat treatment at 700°C and 750°C and 48 hours of heat treatment at 790°C, mixtures containing 9–20 mol% Yb2O3formed a face-centered cubic phase. With the help of X-ray diffraction (XRD), the crystal systems and lattice parameters of the solid solutions were obtained and their characterization was carried out. The surfaces of the solid solutions were detected by a scanning electron microscope (SEM). Thermal measurements were made by using a simultaneous DTA/TGA (differential thermal analysis/thermogravimetric analysis) system. The total conductivity (σT) in the δ-Bi2O3doped with Yb2O3system was measured using the four-probe DC method.

The Akermanite type alkaline earth silicate Ca2MgSi2O7 activated by different types of rare earths was prepared by the conventional solid state reaction method under weak reductive atmosphere. The phase formation, particle size distribution, particle morphologies and photoluminescence properties of the samples have been investigated respectively. The comparative results of SEM and laser particle size analysis revealed that the relatively regular morphology, smaller particle size distribution could be achieved for the phosphors synthesized by the solid state reaction method including dry-ground after which powders were sieved below 170 meshes. The effects of rare earth oxides; Nd2O3, Pr6O11, Ce2O3 and Sm2O3 on the luminescence properties of the host material, Ca2MgSi2O7, were studied. Remarkable enhancement and novel color emitting including white in luminescence characteristics of host material were observed as a result of doping the mentioned rare-earths were doped.

In this research, un-doped CeO2and Ce0.85La0.10M0.05(M: Sm, Er, Y)O2compounds were synthesized by hydrothermal method and the multi-functional properties were reported. Oxygen defects were created with the additives of rare earth ions. The electrical and luminescence behaviors of the synthesized compounds were investigated in accord with the types of additives. The synthesized products were characterizations of the powders achieved by X-ray diffraction analysis (XRD) analysis, Brunauere–Emmette–Teller (BET) measurement, UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopic (EIS). All synthesized compounds were found to be nano-structured and had cubic phase. The total conductivity of all samples was calculated. Hence, the total conductivity of Un-doped CeO2,Ce0.85La0.10Y0.05O2, Ce0.85La0.10Er0.05O2and Ce0.85La0.10Sm0.05O2was found 2.07×10–10, 5.70×10–4, 1.0×10–3and 0.0747 S/cm, respectively. Also, bandgap energy (Eg) of these samples calculated from UV visible absorption spectra was discussed, and the optical results show variation between 3.2 and 2.15 eV. Additionally, the luminescence properties of the compounds were investigated and different emissions occur depending on the additive type. Accordingly, photoluminescent emission spectra of Ce0.85La0.10Y0.05O2, Ce0.85La0.10Er0.05O2and Ce0.85La0.10Sm0.05O2phosphors indicate that these phosphors have red, green and orange-red colors, respectively.

Dy1.98Yb0.02Ti2O7and Lu1.98Er0.02Ti2O7with the cubic pyrochlore structure were prepared at 1050 °C and 1400 °C using solid state reaction method. The crystal structure and unit cell parameters of powder samples were determined by X-ray diffraction method (XRD). Using TG/DTA thermal analysis, we determined the thermal behaviours of starting materials and Curie temperature of fine samples. Dy1.98Yb0.02Ti2O7and Lu1.98Er0.02Ti2O7have high Curie temperature at 770 °C and 765 °C, respectively. To determine morphological structure, elemental composition, photoluminescence properties, dielectric constant, loss tangent, and piezoelectric charge constant of Dy1.98Yb0.02Ti2O7and Lu1.98Er0.02Ti2O7, scanning electron microscope (SEM), photoluminescence spectrophotometer (PL), LCR-meter and d33-meter were used. The results show that Dy1.98Yb0.02Ti2O7and Lu1.98Er0.02Ti2O7are multifunctional materials which show both photoluminescence properties and piezoelectric properties.