Rapid synthesis of thermoelectric YB<sub>22</sub>C<sub>2</sub>N via spark plasma sintering with gas/solid reaction technology - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of the Ceramic Society of Japan Année : 2020

Rapid synthesis of thermoelectric YB22C2N via spark plasma sintering with gas/solid reaction technology

Hyoung-Won Son
  • Fonction : Auteur
Philipp Sauerschnig
  • Fonction : Auteur
Takao Mori

Résumé

Dense YB 22 C 2 N samples were directly synthesized from powder mixtures via reactive spark plasma sintering. The gas/solid reaction step was applied to introduce nitrogen into the mixture during heating. The sample reactively sintered at 1700°C for 10 min after the gas/solid reaction step at 1200°C for 30 min consisted of YB 22 C 2 N with small amounts of secondary phases. The thermoelectric behavior shifted toward n-type behavior with increasing amount of YB 22 C 2 N phase. This newly developed synthesis technique could facilitate the rapid and cost-effective preparation of complex borocarbonitrides. The rare earth borides are a rich class of materials exhibiting interesting structural and physical properties such as superconductivity, magnetism, and thermoelec-tricity, for example. 1)9) The homologous series of rare earth borocarbonitrides; RB 15.5 CN, RB 22 C 2 N, RB 28.5 C 4 were found to exhibit unexpectedly strong magnetic coupling for dilute magnetic insulators, 10),11) and interesting two-dimensional (2D) spin glass-like behavior. 12)14) This series of compounds were also found to be the long-awaited thermoelectric n-type counterpart to boron carbide. 15)17) Despite the attractive properties, the synthesis of these compounds has always been noted to be difficult, necessitating a complex and time consuming process (²9 steps; ²4 days) involving long-time sintering (²10 h), typically multiple re-sintering, crushing and washing processes. 10),18)20) Densification of the material was also found to be difficult, with initial spark plasma sintering (SPS) experiments only yielding a maximum ³75% density. 16) Several sintering aids were found to lead to highly densified samples, but these additives were found to be detrimental to the thermoelectric properties. 19),20) In this study, we report on the first attempt of direct synthesis of complex borocarbonitrides through reactive SPS with gas/solid reaction. A new synthesis method for YB 22 C 2 N from raw materials (except N) was developed to shorten the synthesis time and to attain dense samples. In order to introduce nitrogen into the mixture and to help the formation of the objective phase, gas/solid reaction technology was used during the heating process. Such in situ nitridation during SPS has already been reported for titanium alloy-based composites, 21) but to our knowledge, this is the first example of direct nitride synthesis of borocarbonitrides through reactive SPS. Commercially available YB 4 (99.9%, Japan New Metals Co., Ltd.), amorphous B (99%, New Metals and Chemicals Co., Ltd.) and graphite (Sigma-Aldrich Co., Ltd.) powders were used as the starting materials. The powders were simply mixed under ethanol using an agate mortar with the initial nominal composition; Y 0.73 B 22 C 2 , which corresponds to the average refined composition in the previous reports. 10),18) After drying, the powder mixtures were reactively sintered using an SPS machine (Dr. Sinter, Fuji Denpa Koki Co., Ltd.), as shown in Fig. 1. For sintering, the mixtures were poured into a 10 mm diameter graphite die and pressed using graphite punches. A graphite paper was used as a release agent for ejecting the sample from the graphite die after sintering, and no BN was used. The sintering was carried out in a two-step process at the temperatures of T1 and T2. The mixtures were heated up to T1 of 11001300°C in vacuum to remove volatile gases and B 2 O 3 from surface oxidation of amorphous B, and then kept for 060 min in reduced N 2 gas atmosphere (¹0.03 MPa) to introduce nitrogen into the mixtures. After that, they were heated up to T2 of 1650 1750°C, and then kept for 010 min under a uniaxial pressure of ³30 MPa.
Fichier principal
Vignette du fichier
128_19216.pdf (2.41 Mo) Télécharger le fichier
Origine : Publication financée par une institution
Loading...

Dates et versions

hal-02991413 , version 1 (09-11-2020)

Licence

Paternité - Pas de modifications

Identifiants

Citer

Hyoung-Won Son, Philipp Sauerschnig, David Berthebaud, Takao Mori. Rapid synthesis of thermoelectric YB22C2N via spark plasma sintering with gas/solid reaction technology. Journal of the Ceramic Society of Japan, 2020, 128 (4), pp.181-185. ⟨10.2109/jcersj2.19216⟩. ⟨hal-02991413⟩

Collections

CNRS INC-CNRS LINK
45 Consultations
28 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More