Reactive yttrium aluminate garnet powder via coprecipitation using ammonium hydrogen carbonate as the precipitant

2000 ◽  
Vol 15 (9) ◽  
pp. 1864-1867 ◽  
Author(s):  
Ji Guang Li ◽  
Takayasu Ikegami ◽  
Jong-Heun Lee ◽  
Toshiyuki Mori ◽  
Yoshiyuki Yajima
Keyword(s):  
Theoretical Density ◽  
Mixed Solution ◽  
Vacuum Sintering ◽  
Ammonium Hydrogen Carbonate ◽  
Yttrium Aluminate ◽  
Intermediate Phases ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Approximate Composition ◽  
Carbonate Precursor

Ammonium hydrogen carbonate was used as the precipitant to synthesize yttrium aluminate garnet (YAG) precursors from a mixed solution of aluminum and yttrium nitrates via coprecipitation. The carbonate precursor, with an approximate composition of NH4AlY0.6(CO3)1.9(OH)2 · 0.8H2O, transformed to pure YAG at 900 °C without the formation of intermediate phases. Reactive YAG powder was produced by calcining the precursor at 1100 °C. The YAG powder densified to 99.8% of the theoretical density by vacuum sintering at 1500 °C for 2 h, and the sintered body showed transparency. Less agglomeration of the precursor and good dispersity of the resultant YAG powder were responsible for the excellent sinterability.

Well-sinterable Y3Al5O12 Powder from Carbonate Precursor

2000 ◽  
Vol 15 (7) ◽  
pp. 1514-1523 ◽  
Author(s):  
Ji-Guang Li ◽  
Takayasu Ikegami ◽  
Jong-Heun Lee ◽  
Toshiyuki Mori
Keyword(s):  
Precipitation Method ◽  
Yttrium Nitrate ◽  
Mixed Solution ◽  
Formation Temperature ◽  
Constant Heating Rate ◽  
Vacuum Sintering ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Constant Heating ◽  
Carbonate Precursor

Carbonate precursors of Y3Al5O12 (YAG) were synthesized from a mixed solution of alum and yttrium nitrate using ammonium hydrogen carbonate as precipitant. Precipitation method (normal-strike or reverse-strike) and aging were found to have dramatic effects on cation homogeneity of the precursor, which in turn influenced the formation temperature of the YAG phase. Reactive YAG powders were produced from the reverse-strike-derived, as-synthesized precursors at temperatures ≤1200 °C. These powders densified to >98.0% of the theoretical density up to 1500 %C at a constant heating rate of 8 %C/min or to transparency by vacuum sintering at 1700 %C for 1 h without additives.

scholarly journals Fabrication of Dy2O3 Transparent Ceramics by Vacuum Sintering Using Precipitated Powders

2020 ◽  
Vol 7 (1) ◽  
pp. 6
Author(s):  
Dianjun Hu ◽  
Xin Liu ◽  
Ziyu Liu ◽  
Xiaoying Li ◽  
Feng Tian ◽  
...  
Keyword(s):  
Near Infrared ◽  
Optical Quality ◽  
Precipitation Method ◽  
Infrared Range ◽  
Transparent Ceramics ◽  
Vacuum Sintering ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Liquid Precipitation ◽  
Near Infrared Range

As a kind of promising material for a Faraday isolator used in the visible and near infrared range, Dy2O3 transparent ceramics were prepared by vacuum sintering from the nano-powders synthesized by the liquid precipitation method using ammonium hydrogen carbonate as precipitant with no sintering aids. The synthesized precursor was calcinated at 950 °C–1150 °C for 4 h in air. The influences of the calcination temperature on the morphologies and phase composition of Dy2O3 powders were characterized. It is found that the Dy2O3 powder calcinated at 1000 °C for 4 h is superior for the fabrication of Dy2O3 ceramics. The Dy2O3 transparent ceramic sample prepared by vacuum sintering at 1850 °C for 10 h, and subsequently with air annealing at 1400 °C for 10 h, from the 1000 °C-calcined Dy2O3 powders, presents the best optical quality. The values of in-line transmittance of the optimal ceramic specimen with the thickness of 1.0 mm are 75.3% at 2000 nm and 67.9% at 633 nm. The Verdet constant of Dy2O3 ceramics was measured to be −325.3 ± 1.9 rad/(T·m) at 633 nm, about 2.4 times larger than that of TGG (Tb3Ga5O12) single crystals.

Crystal Structure Stabilization of Gadolinium Aluminum Garnet (Gd3Al5O12) and Photoluminescence Properties

2013 ◽  
Vol 544 ◽  
pp. 245-251 ◽  
Author(s):  
Jin Kai Li ◽  
Ji Guang Li ◽  
Xiao Li Wu ◽  
Shao Hong Liu ◽  
Xiao Dong Li ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thermal Decomposition ◽  
Solid Solutions ◽  
Elevated Temperatures ◽  
Particle Morphology ◽  
Mixed Solution ◽  
Photoluminescence Properties ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Structure Stabilization

To suppress the thermal decomposition and to stabilize the crystal structure of Gd3Al5O12 (GdAG) garnet, doping GdAG with smaller Ln3+ (Ln=Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, respectively) to form (Gd,Ln)AG solid solutions was proposed in work. Carbonate precursors of (Gd,Ln)AG with an approximate composition of (NH4)x(Gd,Ln)3Al5(OH)y(CO3)z•nH2O were synthesized via coprecipitation from a mixed solution of ammonium aluminum sulfate and rare earth nitrate, using ammonium hydrogen carbonate as the precipitant. The precursors and the calcination derived oxides were characterized using FT-IR spectroscopy, DTA/TG, XRD, BET and FE-SEM. The results showed that smaller Ln3+ doping can indeed stabilize GdAG against its thermal decomposition to a mixture of GdAlO3 (GdAP) and Al2O3 phases at elevated temperatures and at the same time effectively lowers the temperature for garnet crystallization. The carbonate precursors are loosely agglomerated and the resultant (Gd,Ln)AG powders show good dispersion and a fairly uniform particle morphology. The (Gd,Ln)AG solid solutions exhibit decreasing lattice parameters along with decreasing radius of the dopant ions at the same dopant content of 50 at%. Photoluminescence properties of some of the garnet solid solutions are also studied. The materials developed herein may potentially be used for photoluminescent and scintillation applications.

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