Influence of Heat Treatment Conditions on Crystallization and Thermal Expansion of Las Glass-Ceramics

2010 ◽  
Vol 168-170 ◽  
pp. 1712-1716
Author(s):  
Zhuo Hao Xiao ◽  
Ming Hua Luo
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Heat Treatment Temperature ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
Matrix Glass ◽  
Treatment Conditions ◽  
The Matrix ◽  
Crystal Phases ◽  
Quenching Method

The LAS glass containing P2O5has been prepared by conventional molten quenching method. The influence of heat treatment conditions on crystallization behavior, including phase transformation and microstructure, and thermal expansion coefficient (TEC) of Li2O–Al2O3–SiO2(LAS) glass-ceramics were investigated. DSC, XRD, SEM and TEC were used to detect the microstructure and properties of glass-ceramics under the different heat-treatment conditions. The results show the virgilite crystalline separated firstly from the matrix glass when heat treatment temperature was 850 °C. As the heat treatment temperature increased from 850 °C to 1050 °C, virgilite and β-spodumene were identified as main crystal phases. The TEC of glass-ceramics ranges from 0.5×10-6 °C-1to 2.8×10-6 °C-1, which is much lower than that of matrix glass.

Effect of NaNbO3 Crystalline Aggregates on the Electrical Properties of SiO2-Na2O-Nb2O5 Glass-Ceramics

2006 ◽  
Vol 514-516 ◽  
pp. 274-279 ◽  
Author(s):  
Manuel P.F. Graça ◽  
Maria Gracinda Ferreira da Silva ◽  
Manuel A. Valente
Keyword(s):  
Heat Treatment ◽  
Electrical Properties ◽  
Heat Treatment Temperature ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
Treated Sample ◽  
Dc And Ac Conductivity ◽  
Potential Applications ◽  
Quenching Method ◽  
Crystalline Aggregates

The presence of NaNbO3 crystallites in a glass matrix has scientific and technological interest due to their electrical properties and potential applications in microwave, pyroelectric and piezoelectric devices. A glass with the composition 60SiO2-30Na2O-10Nb2O5 (% mole) was prepared by the melt-quenching method. NaNbO3 microcrystallites were precipitated on the surface of the glass by heat-treatment. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, dc and ac conductivity measurements were used in the study of the glass and glassceramic materials. The number of particles, precipitated in the surface of the glass-ceramic samples, increases from the 650 to the 750°C and decrease in the 800°C sample. In all these samples the particles size thickness increases with the rise of the heat-treatment temperature. In the 750 and 800°C samples it was observed the presence of a white surface layer formed by NaNbO3 crystallites aggregations. The dc conductivity (σdc) decreases with the rise of the heat –treatment temperature up to 750°C and the dielectric constant value, at 1kHz and room temperature, has a maximum value of 34.94 for the 800 °C treated sample.

Lead titanate glass-ceramics derived from a silicate-based melt

2005 ◽  
Vol 20 (5) ◽  
pp. 1316-1323 ◽  
Author(s):  
P. Sooksaen ◽  
I.M. Reaney ◽  
D.C. Sinclair
Keyword(s):  
Heat Treatment ◽  
Heat Treatment Temperature ◽  
Crystal Size ◽  
Finite Size ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
Finite Size Effects ◽  
Peak Broadening ◽  
Permittivity Measurements ◽  
Nano Size

Glass composition 39PbO–1BaO–25TiO2–9.8Al2O3–24.2SiO2–1B2O3 (mol%) crystallized on heat treatment at ≥600 °C to form glass-ceramics whose majority phase was PbTiO3 (PT). At 600 °C, nano-size PT crystals (∼20–50 nm) with a c/a ratio of 1.000(1) were observed, but as heat-treatment temperature increased to 1000 °C, the crystal size and c/a ratio increased to ∼1.2 μm and 1.056(4), respectively. Permittivity measurements as a function of temperature revealed a broad peak at ∼400 °C associated with the nanocrystalline PT crystals, but it sharpened and increased in temperature as heat treatment temperature increased to 1000 °C. The causes of peak broadening and shift of Tc are believed to be due to either clamping of PT crystals by glass matrix, finite size effects due to their intrinsically small size, or the incorporation of dopant impurities such as Al, Si, or Ba ions in the PT phase.

Effects of Heat-Treatment Temperature on the Properties of Negative CTE Eucryptite Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 123-125 ◽  
Author(s):  
Yong Li ◽  
Qi Hong Wei ◽  
Ling Li ◽  
Chong Hai Wang ◽  
Xiao Li Zhang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Heat Treatment Temperature ◽  
Bending Strength ◽  
Sol Gel ◽  
Negative Thermal Expansion ◽  
Treatment Temperature ◽  
Heat Treated

In this paper, negative thermal expansion coefficient eucryptite powders were prepared by sol-gel method using silica-sol as starting material. The raw blocks were obtained by dry pressing process after the powder was synthesized, and then the raw blocks were heat-treated at 600º, 1150º, 1280º, 1380º, 1420º and 1450°C, respectively. Variations of density, porosity and thermal expansion coefficient at different heat treatment temperatures were investigated. Phase transformation and fracture surface morphology of eucryptite heat-treated at different temperatures, respectively, were observed by XRD and SEM. The results indicate that, with the increasing heat- treatment temperature, the grain size and the bending strength increased, porosity decreased, thermal expansion coefficient decreased continuously. Negative thermal expansion coefficient of -5.3162×10-6~-7.4413×10-6 (0~800°C) was obtained. But when the heat-treatment temperature was more than 1420°C, porosity began to increase, bending strength began to decrease, which were the symbols of over-burning, while the main crystal phase didn’t change.

scholarly journals Effect of heat treatment temperature to the crystal growth and optical performance of Mn3O4 doped α-Zn2SiO4 based glass-ceramics

2019 ◽  
Vol 15 ◽  
pp. 102569
Author(s):  
Mohd Hafiz Mohd Zaid ◽  
Khamirul Amin Matori ◽  
Sidek Hj Ab Aziz ◽  
Halimah Mohamed Kamari ◽  
Yap Wing Fen ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Crystal Growth ◽  
Heat Treatment Temperature ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
Optical Performance

BISMUTH NIOBATE-BASED GLASS-CERAMICS FOR DIELECTRICALLY LOADED MICROWAVE ANTENNAS

2008 ◽  
Vol 01 (01) ◽  
pp. 25-30 ◽  
Author(s):  
MEHDI MIRSANEH ◽  
BEATA ZALINSKA ◽  
OLIVER P. LEISTEN ◽  
IAN M. REANEY
Keyword(s):  
Heat Treatment ◽  
Resonant Frequency ◽  
Glass Ceramic ◽  
Heat Treatment Temperature ◽  
Glass Ceramics ◽  
Treatment Temperature ◽  
Ceramic Processing ◽  
Ceramic System ◽  
Microwave Antennas ◽  
Microwave Applications

A castable, low melting temperature glass-ceramic system (30% Bi 2 O 3, 30% Nb 2 O 5, 30% B 2 O 3 and 10% SiO 2, in mol%) suitable for microwave applications is fabricated and characterized. Depending on heat treatment temperature, the glass ceramic exhibits permittivity, 15 ≤ ε r ≤ 41, temperature coefficient of resonant frequency of -160 ≤ τ f ≤ +100 MK -1 and microwave quality factor of 300 GHz ≤ Qf ≤ 15000 GHz . The highest Qf occurs at 960°C heat treatment with ε r = 15, τ f = -80 MK -1 and Qf = 15000 GHz . Applications are envisaged such as castable dielectrically-loaded antenna pucks, removing the need for complex ceramic processing.

Li2O-Al2O3-SiO2 Glass-Ceramics Used As Anodic Bonding Materials

2008 ◽  
Vol 368-372 ◽  
pp. 1436-1438 ◽  
Author(s):  
Hong Li ◽  
Yun Du ◽  
Jin Shu Cheng ◽  
Tian He Wang
Keyword(s):  
Heat Treatment ◽  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Glass Ceramics ◽  
Treatment Method ◽  
Substrate Material ◽  
Anodic Bonding ◽  
Treatment Schedule ◽  
Crystal Phases ◽  
Step Heat Treatment

The glass-ceramics, whose coefficient of thermal expansion approximately matched to that of silicon, were studied to replace conventional heat-resistant glass as substrate material for anodic bonding. The basic glasses of the Li2O-Al2O3-SiO2 system with TiO2 and ZrO2 as nucleation agents were prepared by melting technology, and the temperatures of nucleation and crystallization were determined. The glass-ceramics were obtained by two-step heat-treatment method. The oriented crystallization of glasses in gradient temperature field was studied. The crystal phases and microstructures of glass- ceramics were analyzed. Effect of heat-treatment schedule on the coefficient of thermal expansion was discussed. The results showed that the most of the main crystal phases of the samples were β-spodumene. The coefficient of thermal expansion of sample was about 32.5×10-7/°C, which was approach to that of silicon.

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