Oxygen-deficiency effect on thermal poling of silica-based glasses (original) (raw)
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Effect of minority species on thermal poling of used silica glasses
High second-order nonlinearity (SON) in poled silica glasses [l] is of great interest for the development of linear electro-optic modulators and frequency converters monolithically integrated into optical fibres or planar glass waveguides. However, its origin [ 1,2] is not fully understood. The extrinsic effects of poling time and voltage on second-harmonic (SH) generation in thermally-poled silica glass have been studied [ 1,3]. In particular the quadratic dependence of the maximum SH signal on the applied voltage indicated linear dependence of the SON on internal electric field [3]. There are several studies on intrinsic effects associated with defects [ 1, 41 and minority species such as OH [ 1,5] and Na [ 1,6] in thermal poling of silica glasses. In this work we carried out a systematic analysis of oxygen related defects and impurities (OH and Na) in commercial fused silica glasses (without relying on their catalogue data) and discuss their effects on SON.
Characterization of thermal poling in silica glasses by current measurements
Journal of Non-Crystalline Solids, 2003
We present herein a charge migration model that predicts the electric field distribution within a Suprasile silica planar sample after poling. The predicted distribution is in agreement with the currents measured at the electrodes during the poling and depoling processes. This electric field is responsible for an apparent second-order non-linear coefficient originating from the third-order one. Numerical values obtained from fits of the experimental curves with the model equations are compatible with the values obtained by optical characterization reported in the literature.
Journal of The American Ceramic Society, 2008
119Sn and 29Si solid-state nuclear magnetic resonance studies on lead silicate glasses containing different amounts of SnO2 confirmed that tin exists in the glass as distorted SnO6 polyhedra and there is no direct interaction between tin and silicon structural units. Transmission electron microscopic studies have established that tin structural units are uniformly distributed in the glass. Significant changes in the values of glass transition temperature, microhardness, and thermal expansion coefficient with SnO2 incorporation into the glass have been attributed to the increased rigidity of the glass network brought about by the replacement of weaker Pb–O linkages with stronger Sn–O linkages.
Optical and thermal properties of (70 − x)SiO2–xNa2O–15CaO–10Al2O3–5TiO2 (10 ≤ x ≤ 25) glasses
Journal of Thermal Analysis and Calorimetry, 2015
The optical and thermal properties are investigated for the (70 − x)SiO2–xNa2O–15CaO–10Al2O3–5TiO2 (10 ≤ x ≤ 25) glasses using different characterization techniques. Kinetic parameters such as glass transition temperature, activation energy of glass transition (Eg), fluctuation-free volume (fg) and change in bulk thermal expansion coefficient (αf) are calculated for better understanding of glass structure. The Eg shows an increasing trend with the increase of Na2O mol%. Correlation has been established between the microvoids in the glass and physical parameters like density and molar volume. Theoretical parameters like optical basicity, oxide polarizability and electro negativities have been obtained and discussed in relation to non-bridging oxygen. Along with the band gap energy, Urbach energy as well as dispersive energy has also been obtained for all the glasses.
Some effects of OH groups on sodium silicate glasses
1970
Glasses of various compositions in the Na2o-sio 2 system were prepared with different levels of OH concentration. Phase separation kinetics, thermal expansion, radiation induced optical absorption, and internal friction of these glasses were studied. The increase in OH content in these glasses was found to (a) enhance the rate of phase separation; (b) increase thermal expansion above the glass temPerature and change the dilatometric softening temperature in a way that depends on microstructure; (c) increase the radiation induced optical absorption bands associated with positive hole centers and decrease those associated with electron trap centers; and, (d) decrease the low temperature alkali peak and increase the high temperature peak of internal friction. Structural changes responsible for the effect of very small amounts of OH on these properties are described. It is imperative to determine and consider OH content in the evaluation of properties which are so significantly affected...
Non-isothermal crystallization kinetics of SiO 2-B 2 O 3-V 2 O 5-Fe 2 O 3-Sm 2 O 3 glass and glass-ceramics are investigated using experimental and theoretical approaches. In order to gain insight into the thermal behaviour of the glasses, Sm 2 O 3 is systematically replaced with Fe 2 O 3 in the glass composition. Differential thermal analysis (DTA) curves of glass and glass-ceramics are obtained at various heating rates. The DTA-derived characteristic temperatures are used as inputs for different theoretical models. Sm 2 O 3 addition in place of Fe 2 O 3 increases the tendency of surface to bulk crystallization with glass formation tendency in the present samples. The highest activation energy of crystallization is observed for the 40SiO 2-40B 2 O 3-10V 2 O 5-10Fe 2 O 3 (SM-0) sample. The activation energy is observed in the range of 220-425 kJ/mol. It is comparable to other glasses.
Journal of Non-crystalline Solids, 2004
The suitability for effective thermal poling of the ternary tellurite glasses with the compositions (100 À 2x)TeO 2 -xBi 2 O 3 -xZnO (x = 5, 10 and 15, in molar percentage) for the second harmonic generation (SHG) was analyzed. The glass transitions and crystallization temperatures were studied via differential thermal analysis. The structural properties of the annealed glasses and furtherly heat-treated samples were probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. Thermal poling of the glasses was undertaken conventionally at various temperatures close to the glass transition temperature under high vacuum and the second harmonic generated signals were compared. A new technique of two stage poling was tested for comparison. The non-linear second harmonic signal of the poled glasses was analyzed using the Maker-fringe technique and it was found that the two stage poling enhanced the non-linear efficiency when compared to the conventionally poled samples.
Journal of Thermal Analysis, 1988
The importance of the thermal behaviour of glasses is illustrated. Some procedural characteristics for ~ass preparation upon quenchinz are discussed to distinguish the positive effects of increasing cooling rate. The basic thermodynamic quantities, kinetic data and procedural parameters are listed. The glass-transformation interval is treated in detail to demonstrate the temperature-dependences of heat capacity, enthalpy an Gibbs energy for as-quenched and annealed glasses, exemplifying processes of thermally stimulated reordering. Particular attention is paid to DTA measurements, which are of use for the determination of characteristic temperatures and to for the distinction of possible types of processes which occur upon reheating. Most common cases are illustrated by a series of hypothetical AH vs. T and ATDTA vs. T plots. Different glass formation coefficients based on the onset temperatures are discussed to confirm the general knowledge that their maxima match with concentration regions close to that of invariant melting of the system.
High Temperature Stability of Sol-Gel-Derived SiOC Glasses
Journal of Sol-gel Science and Technology - J SOL-GEL SCI TECHNOL, 1999
The high temperature stability of sol-gel-derived SiOC glasses has been investigated in order to understand the role played by the presence of a free-carbon phase in the amorphous oxycarbide network. Therefore, pure and excess free-carbon containing SiOC glasses have been prepared from hybrid gels and used for the high temperature stability experiments. Moreover, the possible effects of the sample size with respect to local kinetics and thermodynamics and of the testing environment have also been investigated. Results show that all these parameters play a crucial role in defining the high temperature behavior of SiOC glasses.
Influence of thermal history on the structure and properties of silicate glasses
Journal of Non-Crystalline Solids, 2006
We studied a set of float glass samples prepared with different fictive temperature by previous annealing around the glass transition temperature. We compared the results to previous measurements on a series of amorphous silica samples, also prepared with different fictive temperature. We showed that the modifications on the structure at a local scale are very small, the changes of physical properties are moderate but the changes on density fluctuations at a nanometer scale are rather large: 12 and 20% in float glass and silica, for relative changes of fictive temperature equal to 13 and 25% respectively. Local order and mechanical properties of silica vary in the opposite way compared to float glass (anomalous behavior) but the density fluctuations in both glasses increase with temperature and fictive temperature.