Glasses in the system K2O–TiO2–P2O5 close to KTiOPO4 composition. Part 1: Glass forming ability (original) (raw)
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Glasses in the system K2O–TiO2–P2O5 close to KTiOPO4 composition. Part 2: Crystallization behaviour
The crystallization of K2O–TiO2–P2O5 glasses derived from the KTP composition was studied using DTA, XRD, FTIR and TEM methods. An annealing process of the amorphous glasses in the temperature range between 600°C and 700°C proved to be suited for the precipitation of nanoscale KTiOPO4 crystals. Dependent on the conditions of the heat treatment, KTP crystals are accompanied by a the cubic, low temperature or trigonal, high temperature modification of KTi2(PO4)3 and by K3Ti3(PO4)5 crystals. Introducing 2 mol% of Sb2O5 into the batches to reduce the Ti3+-content of the samples, an accelerated crystal growth and the precipitation of a greater crystal amount is observable. Dopants of Sb2O5 also cause an enhanced surface crystallization, whereas the surface layer mainly consists from K3Ti3(PO4)5 crystals. The determination of n2 values by DFWM measurements shows, that even weak phase formation processes below the XRD detection limit result in an increased Kerr-type nonlinearity of the glasses.
Journal of Non-Crystalline Solids, 2001
Glass formation in the K 2 O±TiO 2 ±P 2 O 5 ±SiO 2 system, and the structure and crystallization behavior of glasses having compositions near the stoichiometry of KTiOPO 4 (KTP) have been examined by dierential thermal analysis (DTA), X-ray diraction (XRD), fast Fourier transform infrared (FTIR) spectroscopy and second harmonic generation (SHG). Pure glasses may be obtained adding an appropriate amount of P 2 O 5 as well as of SiO 2 to the KTP composition. Transparent and homogeneous glasses were synthesized for the 56K 2 O Á 2TiO 2 Á P 2 O 5 Á 44P 2 O 5 (KTP±44P) and the 90K 2 O Á 2TiO 2 Á P 2 O 5 Á 10SiO 2 (KTP±10Si) molar compositions. In contrast, for the 80K 2 O Á 2TiO 2 Á P 2 O 5 Á 20SiO 2 (KTP±20Si) and for higher SiO 2 contents, the obtained glasses were partially opaque and phase separated. KTP glasses with lower P 2 O 5 content cannot be obtained as they crystallize during quenching. The KTP±10Si glass shows the only exothermic peak connected to KTP phase crystallization whereas the KTP±44P and the KTP±20Si glasses devitrify in two steps. Firstly the same unidenti®ed phase is formed in both these glasses and the KTP phase is formed only at higher temperatures. Transparent and opalescent KTP glasses exhibiting SHG activity may be produced by careful heat treatments at temperatures just above T g . The origin of SHG in transparent glasses is supposed to be connected with either precipitation of KTiOPO 4 nanocrystallites or very early stages of liquid-type phase separation. Ó
Structural and crystallization characteristics of K~ 2O· TiO~ 2· 3GeO~ 2 glass
Ceramics- Silikaty, 2005
Structure and crystallization of K 2 O•TiO 2 •3GeO 2 glass have been investigated by means of Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), differential scanning calorimetry (DSC), x-ray diffraction analysis (XRD), and scanning electron microscopy (SEM). XRD analysis of crystallized glass reveals the presence of crystalline K 2 O TiO 2 3GeO 2 indicating the same composition of crystalline and parent glass. For glass particle size > 0.15 mm volume crystallization is dominant crystallization mechanism. SEM investigation of the crystallized glass confirmed volume crystallization of spherical nuclei.
Journal of Non-Crystalline Solids, 2017
Glasses of the system of composition K 2 O-La 2 O 3-Al 2 O 3-SiO 2-P 2 O 5 have recently gained attention due to their response to femtosecond (fs) laser irradiation, and the fact that high repetition rate fs-laser writing allows for the production of very efficient waveguides. When doped with rare-earth ions, the glasses can also be used in amplifiers or lasers and, in this respect, a control of the water content in the phosphate-based glasses is of very high importance. Thus, in the present work we have studied the influence of the melting conditions on the final water content of glasses of the above system and on their structure as studied by Raman and Nuclear Magnetic Resonance spectroscopies. Increasing temperature and melting times conducts to the enrichment in SiO 2 and a depletion of K 2 O and P 2 O 5 contents in parallel with a reduction of the water content as measured by FTIR. On the other hand, the structural study showed that the chemical environment of phosphorous and silicon are not much affected by the changes in composition and that aluminium moves from being 6-fold coordinated to 4-fold. Finally, it has also been observed that SiO 2 enters in the glasses as fully polymerized, which is consistent with the reduction of water directly on the ratio between oxygen and phosphorus in the glasses.
Optical properties and glass-forming region of the K2O-Sm2O3-TeO2 glass system
Journal of the Korean Physical Society, 2014
The optical properties and the glass-forming region of the K2O-Sm2O3-TeO2 glass system are studied. In the K2O-Sm2O3-TeO2 system, only the 5K2O-5Sm2O3-90TeO2 composition gives a transparent glass. The refractive index, n, and the optical band-gap energy, Eg, of the 5K2O-5Sm2O3-90TeO2 glass are n = 2.04 ± 0.003 and Eg = 3.2 eV, respectively. A single Sm2Te6O15 phase is found to be formed by a two-step thermal treatment process at 370 • C for 5 h and 390 • C for 5 h. This is the first report on the crystallization and the preparation of the K2O-Sm2O3-TeO2 glass system.
Crystallization of Glasses Containing K2O, PbO, BaO, Al2O3, B2O3, and TiO2
Crystals
The objective of this work was to obtain glass-ceramics from stable glasses, with a composition of barium, lead, and potassium titanate phases, for use as semiconductors. For this purpose, the glass-ceramic technique was used to control crystal growth and obtain a fine-grained microstructure. Various glasses containing K2O, PbO, BaO, Al2O3, B2O3, and TiO2 were prepared using a melt-quenching method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed a single amorphous phase of all samples. Infrared spectra confirmed the presence of B-O bonds stretching vibrations of (B3O6)3− boroxol rings and BO3 triangles, as well as Ti-O stretching vibrations of (TiO6/2) and (AlO6/2) octahedral units. Thermal analyses confirmed the presence of one or more crystallization peaks in the range of 700 to 744 °C. On this base, they were heat-treated to promote crystal growth. XRD and SEM detected Ba4Ti12O27, Ti7O13, and BaTiO3 phases, homogeneously distributed throughout the material ...
Structural and dielectric properties of K2O-TiO2-P2O5 glass and its associated glass-ceramic
Materials Today: Proceedings
20K 2 O-30TiO 2-50P 2 O 5 (KTP) glass was elaborated by conventional quenching method. The density and molar volume values of KTP glass are determined. The structure of the glass was performed by Raman spectroscopy. The results revealed that KTP glass consists mainly of orthophosphate and pyrophosphate units, and the titanium occupies the octahedral sites in the glassy matrix. The controlled crystallization of KTP glass was carried out to develop glass-ceramic (GC-KTP). X-ray diffraction was used to identify the crystallized phases in (GC-KTP). Dielectric and conductivity parameters of the glass-ceramic are determined by impedance spectroscopy in the frequency range of 300 Hz to 1 MHz under various temperatures from 300 to 473 K. The results obtained showed that the dielectric parameters (permittivity and dielectric losses) increase at high-temperature and low-frequency and the conductivity is thermally activated and follows the Arrhenius behavior.