GeO2 Doping Research Articles

Fabrication and photo-responsive characteristics of GeO2 doped SnO2/porous Si film for ultraviolet photodetector application

In this manuscript, tin oxide (SnO2) and Germanium dioxide (GeO2) doped SnO2/porous silicon (Si) film/s were fabricated using combined co-precipitation and laser pulsed deposition methods for ultraviolet photodetector/s application. X-ray diffraction (XRD) study indicated the occurrence of high crystalline film/s, wherein nanoparticle diameters of 85 and 50 nm were attained using field emission scanning electron microscopy (FE-SEM). The attained optical bandgap for un-doped SnO2 layer was found to be 3.8 eV which was found to be increased to deeper ultraviolet region (4.2 eV) after GeO2 doping. Further, a considerable photo-current value of 148 μA was attained at 396 nm for the GeO2-doped SnO2 photodetector. This in turn was noticed to significantly increased to 165 μA at deeper UV light (365 nm). The recovery time of the un-doped SnO2 photodetector was found to be 710 ms, while adding 25% of GeO2 as dopant resulted in lower recovery rate (615 ms). Along with the robustness and steadiness of the proposed geometry, it reveals an approachable path for cost-effective optoelectronic system.

Analytical investigation of GeO2-doped optical fibers to build Brillouin lasers at 1300 nm

The 1.5 µm spectral region concentrates the most substantial attention on building fiber laser sources for communications applications. However, data transmission in this spectral region is quite congested, requiring exploring new neighboring regions. In particular, 1.3 µm, usually defined as the zero-dispersion band, currently constitutes an active field of research, and the development of fiber laser sources in this wavelength band is of substantial interest to expand the capabilities of existing photonic operations. Previous experimental investigations have already shown that the peak stimulated Brillouin scattering efficiency is strongly affected by the concentration of GeO2 doping in single-mode fibers. In this context, this work presents an analytical investigation of the performance of a Brillouin fiber laser at 1.3 µm using optical fibers doped with different GeO2 concentrations as a Brillouin gain medium. The results obtained suggest that optical fibers doped with high GeO2 concentrations can be a simple and effective solution to build Brillouin lasers with better efficiency in the 1.3 µm band employing shorter fiber lengths with low pump power values.

Magnetic properties of CCTO doped with GeO2

The high dielectric constant presented by CaCu3Ti4O12 (CCTO) makes this material promising for industrial applications, in particular for electronic devices. Nevertheless, the preparation method and the doping by oxides has a great influence on the microstructure, and consequently in the dielectric properties. In this work we prepared and studied CCTO doped by germanium oxide, in concentrations up to 10% by weight. X-ray diffraction shows the presence of nanocristals. The grains and the grain boundaries compositions have been characterized by scanning electron microscopy with energy dispersive X-ray spectrometry mapping. The magnetization measurements show an antiferromagnetic behaviour with a Néel temperature TN=25 K, independent of the GeO2 doping (up to 6%). Analyses of the high temperature dependence of the magnetic susceptibility show that the increase of the GeO2 doping decreases the paramagnetic temperature. Dielectric spectroscopy measurements, in the frequency range from 75 kHz to 30 MHz, at room temperature, have been carried out. Cole-Cole model of dielectric relaxation adjusts correctly the data. The results, obtained with the different techniques, indicate that there is the increase of samples grain size up to 6% of germanium oxide, which causes an increase of the real and imaginary parts of complex permittivity.

Enhanced mechanical quality factor of BiScO3-PbTiO3 piezoelectric ceramics using glass composition.

Compared with pure Pb-based perovskite ferroelectric materials, Bi(Me)O3–PbTiO3 (Me = Sc3+, In3+, Yb3+) have attracted attention due to their remarkable advantage in their Curie temperature. Among them, BiScO3–PbTiO3 piezoelectric ceramic is a potential piezoelectric material in high-temperature applications for its high Curie temperature and excellent piezoelectric coefficient. However, its shortcomings are high dielectric loss and low mechanical quality factor. Herein, we report the improvement of the mechanical quality factor of 0.36BS–0.64PT ceramics through the addition of glass composition (GeO2). There is a small change in the Curie temperature after GeO2 addition. The piezoelectric coefficient d33 and planar electromechanical coupling factor kp increase first and then decrease, and the mechanical quality factor Qm monotone increases with an increase in GeO2. The 0.36BS–0.64PT + 0.5 mol%GeO2 ceramics have optimal electrical properties with TC of 455 °C, d33 of 385 pC N−1, kp of 58%, and Qm of 90. In addition, the thermal stability of 0.36BS–0.64PT + xGeO2 and 0.36BS–0.64PT ceramics is almost the same. It was concluded that the mechanical quality factor of BS–PT ceramics can be enhanced by the addition of GeO2 with other properties remaining unchanged.

GeO2 Modified High-Concentration Er3+/Yb3+ Co-Doped Phosphate Glasses for 1.5 μm High Gain Laser

The GeO2 modified high-concentration Er3+/Yb3+ co-doped phosphate glasses with composition 64P2O5–2ZnO–13BaCO3–13K2CO3–8Al2O3–0.5Er2O3–12Yb2O3–xGeO2 mol% (PEYG, x = 0, 2.5, 5, 7.5, and 10) were successfully prepared by the melt-quenching method. The structure and spectroscopic properties were revealed by analyzing refractive index, expansion coefficient, glass transition temperature, absorption and emission spectra, and laser properties. We studied the relationship between GeO2 doping content and spectroscopic properties, finding that GeO2 could enhance 1535 nm emission of the PEYG glasses. The PEYG modified with 5 mol% GeO2 showed the best spectroscopic properties. The study provided a good guidance for the design of high gain laser glasses and fibers.

Towards athermal Brillouin strain sensing based on heavily germania-doped core optical fibers

Owing to their interesting linear and nonlinear optical properties, germania-based core optical fibers are being widely used in a wide range of applications ranging from nonlinear optics to optical sensing. We here examine both the strain and temperature coefficients of stimulated Brillouin scattering in heavily doped core optical fibers with ultrahigh GeO2 doping level up to 98-mol. %. Our results show that the temperature dependence of the Brillouin gain spectrum becomes almost negligible (CT = 0.07 MHz/°C) for high doping content, while its Brillouin strain coefficient remains significant (Cε = 21.4 kHz με−1) compared to that of standard single-mode optical fibers (Cε = 48.9 kHz με−1). It is further shown that the temperature coefficient tends to zero when removing the fiber coating, indicating that those athermal highly GeO2-doped-core optical fibers could advantageously be used for Brillouin fiber strain sensing.

Pressure-independent Brillouin Fiber Optic Sensors for temperature measurements

Fiber Optic Sensors (FOSs) based on Brillouin scattering are widely used in large infrastructures to detect modifications over large distances. In doped silica fibers the Brillouin Frequency Shift (BFS) is proportional both to temperature and strains. In this work we establish that the sensitivity of FOSs to hydrostatic pressure can be forecast from the behavior of the glass under hydrostatic compressions in a diamond anvil cell. It is shown that the BFS under a hydrostatic pressure is a manifestation of the elastic anomaly observed in silica glass. This anomaly vanishes in GeO2 glass and accounts for the decrease of the sensor sensitivity when the GeO2 doping concentration increases in a silica fiber. The progressive vanishing of the anomaly in sodium aluminosilicate glasses which contain the same amount of silicon dioxide (75%) but differ in the Na2O and Al2O3 ratio allows to determine the composition of a glass with a BFS independent of the pressure. Such a glass composition will provide a pressure-independent temperature FOSs.

Efficient one-third harmonic generation in highly Germania-doped fibers enhanced by pump attenuation

We provide a comprehensive study on one-third harmonic generation (OTHG) in highly Germania-doped fiber (HGDF) by analyzing the phase matching conditions for the step index-profile and optimizing the design parameters. For stimulated OTHG in HGDF, the process can be enhanced by fiber attenuation at the pump wavelength which dynamically compensates the accumulated phase-mismatch along the fiber. With 500 W pump and 35 W seed power, simulation results show that a 31% conversion efficiency, which is 4 times higher than the lossless OTHG process, can be achieved in 34 m of HGDF with 90 mol. % GeO2 doping in the core.

Microstructure and Electrical Properties of BaFe0.5Nb0.5O3 Doped with GeO2 (1–5 wt.%)

In this work, the effects of GeO2 dopant on the electrical properties of BaFe0.5Nb0.5O3 (BFN) perovskite ceramics were investigated. The BFN powder was prepared by a conventional mixed-oxide method using stoichiometric amounts of BaCO3, Fe2O3 and Nb2O5. Afterward the GeO2 contents, ranging from 1 to 5 wt.%, were added to the calcined BFN powder and mixed via vibro-milling method. The mixtures were pressed and sintered at 1125–1150°C for 4 h to form dense ceramics. We showed that the addition of GeO2 caused a reduction of grain size and formation of secondary phases: Ba3Fe2Ge4O14 and BaGeO3. The maximum densities of these BFN doped with GeO2 ceramics were slightly lower than those of the pure BFN due to the occurrence of pores. We also found that the GeO2 doping could improve the dielectric properties of these ceramics at room temperature (25°C). The 1 wt.% GeO2 doped sample exhibited higher dielectric constant of about 1800 and lower dielectric loss of 0.45 comparing to that of pure BFN. However, the dielectric constant values of these ceramics at high temperature (>25°C) were decreased significantly with the increase of GeO2 concentration. In addition, the GeO2 additive gave a weak ferroelectric behavior, leading to change in the pyroelectric coefficient and spontaneous polarization of the GeO2 doped BFN ceramics.

正方晶 ZrO<sub>2</sub> 多結晶体の高温変形における TiO<sub>2</sub> 及び GeO<sub>2</sub> 添加量依存性

The doping dependence of high temperature plastic flow behavior in TiO2-doped, GeO2-doped and TiO2 and GeO2 co-doped tetragonal ZrO2 polycrystal (TZP) was systematically examined at 1400°C in air under an initial strain rate of 1.3×10-4 s-1. The amount of dopant cations was in the range of 0.2-4 mol%. The flow stress in the TZP decreases with the increasing doping amount in TiO2 and/or GeO2-doped TZP, but levels off over a 3 mol% addition in the GeO2-doped and TiO2-GeO2 co-doped TZP. The doping dependence of the flow stress in the TiO2-GeO2 co-doped TZP is close to that in the GeO2-doped TZP rather than to that in the TiO2-doped TZP; the flow stress in the GeO2-doped and TiO2-GeO2 co-doped TZP is significantly lower than that in the TiO2-doped TZP. The doped cations tend to segregate in the vicinity of the grain boundaries in TZP. The doping dependence of the flow stress is probably related to the amount of the grain boundary segregation of the dopant cations; the grain boundary segregation of the dopant cations is supposed to enhance the grain boundary atomic diffusion in the TZP, and hence the flow stress consequently decreases. On the other hand, elongation to failure in the TZP is highly improved by the TiO2 and/or GeO2 doping. The improved high temperature ductility of the TZP is attributed to the flow stress reduction due to the TiO2 and/or GeO2 doping.

Enhancement of stimulated Brillouin scattering of higher-order acoustic modes in single-mode optical fiber

Solving the elastic wave equation exactly for a GeO2-doped silica fiber with a steplike distribution of the longitudinal and shear velocities and density, we have obtained the dispersion, attenuation, and fields of the leaky acoustic modes supported by the fiber. We have developed a model for stimulated Brillouin scattering of these modes in a pump-probe configuration and provided their Brillouin gains and frequencies for an extended range of core sizes and GeO2 doping. Parameter ranges close to cutoff of the acoustic modes and pump depletion enhance the ratio of higher-order peaks to the main peak in the Brillouin spectrum and are suitable for simultaneous strain-temperature sensing.

The effect of surface GeO 2-doping and CeO 2-doping on the degradation of 2Y-TZP ceramic on annealing in water at 200°C

The bending strengths of 2Y-TZP ceramics treated by different methods were compared after annealing in water at 200°C. Surface GeO 2- and CeO 2-doped materials did not show the decrease in bending strength shown when GeO 2 and CeO 2 are doped through the bulk 2Y-TZP ceramic. This behavior is attributed to surface doping leading to an improvement in the resistance of Y-TZP to low temperature hydrothermal corrosion. The thermal stability of 2Y-TZP can be improved by surface doping without loss of fracture strength when the doped layer is less than the critical flaw length.