Mineralizing Spinel Formation with Boron-Containing Compounds

2006 ◽  
Vol 45 ◽  
pp. 2254-2259
Author(s):  
Goutam Bhattacharya ◽  
Shao Wei Zhang ◽  
Daniel Doni Jayaseelan ◽  
William Edward Lee
Keyword(s):  
Grain Growth ◽  
Boron Oxide ◽  
Borate Glass ◽  
Single Phase ◽  
Sodium Tetraborate ◽  
Lithium Tetraborate ◽  
Templated Grain Growth ◽  
Spinel Formation ◽  
Phase Spinel ◽  
Spinel Mgal2o4

Spinel (MgAl2O4) formation from stoichiometric MgO and Al2O3 is strongly mineralized by B-containing compounds such as boron oxide (B2O3), lithium tetraborate (Li2B4O7) and sodium tetraborate (Na2B4O7) at 1000°C. TEM confirms that the mineralization with each compound involves borate glass which is presumably formed on cooling from liquid at 1000°C. EDS shows the boron-containing liquids formed from B2O3 and Na2B4O7-mineralized samples contain little alumina suggesting a templated grain growth whereas those in Li2B4O7-mineralized samples dissolve sufficient alumina to suggest dissolution-precipitation is occurring at this temperature. XRD shows that Li2B4O7 is the most effective mineralizer producing single- phase spinel with 3 wt% addition at 1000°C whereas B2O3 produces Mg3B2O6 at 1.5 wt% addition and both B2O3 and Na2B4O7- mineralized samples show incomplete spinelisation which may be explained by the composition of the liquids formed with these two mineralizers.

Effect of magnesium on relaxation frequency of Ni–Zn nanoferrites

2015 ◽  
Vol 29 (30) ◽  
pp. 1550218 ◽  
Author(s):  
D. R. S. Ganga Swamy ◽  
M. Chaitanya Varma ◽  
S. Bharadwaj ◽  
K. Sambasiva Rao ◽  
K. H. Rao
Keyword(s):  
Grain Growth ◽  
Single Phase ◽  
Sol Gel ◽  
Chelating Agent ◽  
Magnesium Content ◽  
Magnesium Concentration ◽  
X Ray Diffraction ◽  
High Permeability ◽  
Low Concentrations ◽  
Phase Spinel

[Formula: see text] (x = 0, 0.4, 0.8, 0.10, 0.12 and 0.16) samples have been synthesized by sol–gel method using polyvinyl alcohol (PVA) as chelating agent. The synthesized samples were sintered at 1000[Formula: see text]C for 1 h. The X-ray diffraction (XRD) confirms single phase spinel structure and scanning electron microscope (SEM) confirms the uniform grain with increasing grain growth with increase concentration of magnesium (Mg) (x). A slight increase in saturation magnetization (VSM) has been observed for low concentrations of magnesium which disappear for higher concentrations of magnesium [Formula: see text] in these materials. Decrease in room temperature DC resistivity with magnesium concentration has been attributed to grain growth. The permeability measured for the ferrites exhibits high permeability for increase in the magnesium content. The permeability behavior is understood on the basis of domain wall contribution and grain growth. Frequency dependence of permeability as measured suggests that the suitability of all the samples for high frequency core applications as the operating frequency lies beyond 110 MHz.

Fabrication and Microstructure of Grain-Oriented (Bi1/2K1/2)TiO3 Ceramics

2010 ◽  
Vol 445 ◽  
pp. 15-18 ◽  
Author(s):  
Masahiro Saitoh ◽  
Yuji Hiruma ◽  
Hajime Nagata ◽  
Tadashi Takenaka
Keyword(s):  
Grain Growth ◽  
Hot Pressing ◽  
Perovskite Structure ◽  
Single Phase ◽  
Density Ratio ◽  
High Density ◽  
Orientation Factor ◽  
Templated Grain Growth ◽  
High Density Ratio ◽  
High Orientation

Grain-oriented (Bi1/2K1/2)TiO3 (BKT) ceramics were prepared by the reactive templated grain growth (RTGG) method, and a hot-pressing (HP) method was modified on the basis of the RTGG method to obtain dense ceramics. The BKT ceramic sintered at 1060°C showed a single-phase perovskite structure. The grain-oriented BKT prepared by the HP method exhibited a relatively high orientation factor F of 0.82 and a high density ratio of 99%. SEM micrographs of the HP-grain-oriented BKT indicated a textured and poreless microstructure. On the basis of the density ratio of 87% for the grain-oriented BKT without HP, the HP method was considered very effective for improving the density ratio even for the RTGG sample. In addition, the resistivity of the HP-grain-oriented BKT was 1.73 x 1013 •cm.

Fabrication of Lead-Free Piezoelectric Ceramics by (Reactive) Templated Grain Growth

2010 ◽  
Vol 1 (3) ◽  
pp. 241-248 ◽  
Author(s):  
Wei Zhao ◽  
Jing Ya ◽  
Ying Xin ◽  
Zhifeng Liu ◽  
Lei E. ◽  
...  
Keyword(s):  
Grain Growth ◽  
Piezoelectric Ceramics ◽  
Lead Free ◽  
Templated Grain Growth

Texture Development in KSr2Nb5O15 Ceramics Fabricated by Reactive Templated Grain Growth

2004 ◽  
Vol 264-268 ◽  
pp. 1285-1288 ◽  
Author(s):  
K. Yurdal ◽  
Cihangir Duran ◽  
S. Alkoy ◽  
H.I. Bakan
Keyword(s):  
Grain Growth ◽  
Texture Development ◽  
Templated Grain Growth

Effect of Excess PbO on the Kinetics of the Growth of PMNT Polycrystals by Templated Grain Growth Method

2005 ◽  
Vol 475-479 ◽  
pp. 1137-1140
Author(s):  
Lili Zhao ◽  
Feng Gao ◽  
Wei Min Wang ◽  
Chang Sheng Tian
Keyword(s):  
Grain Growth ◽  
Templated Grain Growth ◽  
Experimental Conditions ◽  
Precipitation Mechanism ◽  
Oriented Structure ◽  
Diffusion Controlled ◽  
The Matrix ◽  
Growth Method ◽  
Final Composition ◽  
Kinetics Of

The oriented 0.67Pb (Mg1/3Nb2/3)O3-0.33PbTiO3 (PMNT) polycrystals were prepared by the conventional ceramic technique and the templated grain growth method adding excess PbO in the matrix. Kinetics of the development of oriented structure was investigated systemically. In the presence of PbO liquid phase, the oriented PMNT polycrystals mainly grow by the dissolution-precipitation mechanism. The diffusion is determined by the sintering temperature and the PbO-excess content in the matrix. The thickness of oriented PMNT polycrystals displays a t1/3 dependence, which is characteristic of diffusion-controlled growth. For the thicker oriented structure, 20% excess PbO in the PMNT matrix and 1150oC for 10h are the proper experimental conditions. Moreover, the addition of PbO in the matrix hardly affects the final composition of ceramic matrix.

A mechanism for deformation-enhanced grain growth in single phase materials

1991 ◽  
Vol 25 (12) ◽  
pp. 2873-2878 ◽  
Author(s):  
D.J. Sherwood ◽  
C.H. Hamilton
Keyword(s):  
Grain Growth ◽  
Single Phase
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