Thermal conversion in air of rare-earth fluorides to rare-earth oxyfluorides and rare-earth oxides

2022 ◽  
pp. 153538
Author(s):  
Saehwa Chong ◽  
Brian J. Riley
2010 ◽  
Vol 105-106 ◽  
pp. 171-174 ◽  
Author(s):  
Bai Bing ◽  
Teng Fu ◽  
Xiao Shan Ning

In this paper, rare-earth fluorides were used as sintering additives instead of rare-earth oxides, the influence of the type and the amount of the fluoride on the thermal conductivity, hardness and strength of Si3N4 ceramics was studied. Results show that the thermal conductivity of a sample sintered with CeF3 is nearly 10% higher than that of the sample sintered with Ce2O3, while the samples sintered with LaF3 increases further 15% as comparing with the samples sintered with CeF3. The strength of the samples changes reversely. These results express that the thermal conductivity of Si3N4 ceramics can be improved by using rare-earth fluoride additives instead of the oxides, and the type of rare-earth fluorides has a significant impact on the properties of Si3N4 ceramics.


Author(s):  
N. M. P. Low ◽  
L. E. Brosselard

There has been considerable interest over the past several years in materials capable of converting infrared radiation to visible light by means of sequential excitation in two or more steps. Several rare-earth trifluorides (LaF3, YF3, GdF3, and LuF3) containing a small amount of other trivalent rare-earth ions (Yb3+ and Er3+, or Ho3+, or Tm3+) have been found to exhibit such phenomenon. The methods of preparation of these rare-earth fluorides in the crystalline solid form generally involve a co-precipitation process and a subsequent solid state reaction at elevated temperatures. This investigation was undertaken to examine the morphological features of both the precipitated and the thermally treated fluoride powders by both transmission and scanning electron microscopy.Rare-earth oxides of stoichiometric composition were dissolved in nitric acid and the mixed rare-earth fluoride was then coprecipitated out as fine granules by the addition of excess hydrofluoric acid. The precipitated rare-earth fluorides were washed with water, separated from the aqueous solution, and oven-dried.


2015 ◽  
Vol 30 (3) ◽  
pp. 267
Author(s):  
HUANG Lin-Yun ◽  
LI Chen-Hui ◽  
KE Wen-Ming ◽  
SHI Yu-Sheng ◽  
HE Zhi-Yong ◽  
...  

2020 ◽  
Vol 05 ◽  
Author(s):  
Silas Santos ◽  
Orlando Rodrigues ◽  
Letícia Campos

Background: Innovation mission in materials science requires new approaches to form functional materials, wherein the concept of its formation begins in nano/micro scale. Rare earth oxides with general form (RE2O3; RE from La to Lu, including Sc and Y) exhibit particular proprieties, being used in a vast field of applications with high technological content since agriculture to astronomy. Despite of their applicability, there is a lack of studies on surface chemistry of rare earth oxides. Zeta potential determination provides key parameters to form smart materials by controlling interparticle forces, as well as their evolution during processing. This paper reports a study on zeta potential with emphasis for rare earth oxide nanoparticles. A brief overview on rare earths, as well as zeta potential, including sample preparation, measurement parameters, and the most common mistakes during this evaluation are reported. Methods: A brief overview on rare earths, including zeta potential, and interparticle forces are presented. A practical study on zeta potential of rare earth oxides - RE2O3 (RE as Y, Dy, Tm, Eu, and Ce) in aqueous media is reported. Moreover, sample preparation, measurement parameters, and common mistakes during this evaluation are discussed. Results: Potential zeta values depend on particle characteristics such as size, shape, density, and surface area. Besides, preparation of samples which involves electrolyte concentration and time for homogenization of suspensions are extremely valuable to get suitable results. Conclusion: Zeta potential evaluation provides key parameters to produce smart materials seeing that interparticle forces can be controlled. Even though zeta potential characterization is mature, investigations on rare earth oxides are very scarce. Therefore, this innovative paper is a valuable contribution on this field.


2014 ◽  
Vol 95 ◽  
pp. 175-180
Author(s):  
Takuya Agou ◽  
Hiroya Imao

It is necessary to formpinning centers in superconductors to allow the flow of large currents throughthe specimens. To clarify the properties of pinning centers, it is preferableto investigate single crystals. In this study, heat treatment was used to dopevarious oxides into Bi2Sr2CaCu2Ox(Bi-2212) single crystals prepared by self-flux methods and the criticalcurrent (Ic) was measured. The oxides used in this study were Al2O3and the rare earth oxides Er2O3and Nd2O3. At 77K, Nd2O3and Er2O3 are magnetic, whereas Al2O3is nonmagnetic. The Ic of the samples were measured as a current per width of 1cm (Ics). The resulting Ics of the Bi-2212 single crystal was 2.8A/cm and thatof the Al2O3 doped Bi-2212 sample was 4.5A/cm. Comparedwith these samples, doping the other rare earth oxides gave Ics values inexcess 10A/cm. The results indicated that the doping oxides were effective inoperating as pinning centers in the samples. We assumed the current path in asingle crystal, and calculated the Ics by superconducting current simulation.The results indicated that the oxides permeated from a crystal surface in aporous shape. The oxides increase the current which flow in the Cu-O2planes that are parallel to the a-b plane.


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