Synthesis and Sintering of Cerium(III) Sulfide Powders

Abstract

Cerium(III) sulfide (Ce 2 S 3 ) powder was synthesized via the sulfurization of ceria (CeO 2 ) powder using carbon disulfide gas. Single-phase ␣-Ce 2 S 3 could be formed via sulfurization at 973 K for 28.8 ks. The preparation of ␣-Ce 2 S 3 became feasible at low temperature, in comparison to sulfurization using hydrogen sulfide gas. According to the fact that the formation of ␣-Ce 2 S 3 was accelerated by the addition of carbon black to the CeO 2 powder, carbothermic reduction was considered to become a dominant reaction, as the temperature increased. To obtain the activation energy for the densification of ␤-Ce 2 S 3 powder, which was prepared by vacuum heating ␣-Ce 2 S 3 , the data of densification by hot pressing was analyzed by a kinetic equation that was proposed by other researchers. As a result, the sintering behavior could be best explained by a grain-boundarydiffusion mechanism that had an apparent activation energy of 382 kJ/mol.

Thermal Decomposition of NH<SUB>4</SUB>SCN for Preparation of Ln<SUB>2</SUB>S<SUB>3</SUB> (Ln=La and Gd) by Sulfurization

“…It is well known that sulfurization with CS 2 gas is more efficient than that with H 2 S gas. 10,17,19) Therefore, we believe that Ln 2 S 3 is mainly formed by sulfurization with CS 2 gas.…”

“…Carbon disulfide (CS 2 ) and hydrogen sulfide (H 2 S) gases are commonly used as sulfurizing agents. 4,5,7,[10][11][12][13][14][15][16][17][18][19][20] Gases that evolve during the thermal decomposition of ammonium thiocyanate (NH 4 SCN) can also be used as sulfurizing agents. 21) However, sulfurization with NH 4 SCN has not been investigated thoroughly.…”

Synthesis of LnCuS<SUB>2</SUB> (Ln=Ce, Pr, Nd, Sm, Gd, and Tb) Powder by Polymerized Complex Method and CS<SUB>2</SUB> Gas Sulfurization

“…1. 8) Ln-Cu complex oxide was placed in a quartz boat and inserted into a quartz tube (a reaction vessel). The reaction vessel was vacuumed and then flushed by argon gas.…”

Low-Temperature Formation of Cubic Th3P4-type Gadolinium and Holmium Sesquisulfides

“…The experimental apparatus used for sulfurization in the present study are the same as described in our previous paper 6) . The starting material powders were placed in a silica boat and inserted into a silica glass tube.…”