Densification of MnSO4 ceramics by Cool-SPS: Evidences for a complex sintering mechanism and magnetoelectric coupling

Thomas Hérisson de Beauvoir (1) , F. Molinari (1) , U-Chan Chung-Seu (1) , Dominique Michau (1) , Dominique Denux (1) , Michaël Josse (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

Dense ceramics of MnSO4 composition have been successfully densified at 400 °C in only 5 min under a uniaxial pressure of 400 MPa, using Spark Plasma Sintering technique. Since the stable form of MnSO4 in ambient atmosphere is its hydrate MnSO4·H2O, crystallizing in a different space group, dehydration is required to reach a purely anhydrous phase. In situ dehydration during Spark Plasma Sintering allows to lower both sintering temperature and time. Applied pressure strongly influences dehydration step and therefore is a key parameter to tune densification, so far as to obtain a dense MnSO4·H2O ceramic. The presence of a reversible phase transition to a β-MnSO4 high temperature form seems to influence the dehydration temperature under pressure, and likely drives the sintering mechanisms. The high densification obtained, beyond 95% of theoretical density, added to the preservation of the structural and physical properties of MnSO4 after sintering allowed to perform reliable and reproducible measurements showing a dielectric anomaly associated to the magnetic transition, and the hysteretic behaviour of capacitance versus magnetic field, which is a clue for an intrinsic magnetoelectric coupling in MnSO4.

Mots clés: Low temperature; Spark Plasma Sintering; Cool-SPS; Magnetoelectric; Ceramics

Domaines: Matériaux

Thomas Hérisson de Beauvoir, F. Molinari, U-Chan Chung-Seu, Dominique Michau, Dominique Denux, et al.. Densification of MnSO4 ceramics by Cool-SPS: Evidences for a complex sintering mechanism and magnetoelectric coupling. Journal of the European Ceramic Society, 2018, 38 (11), pp.3867-3874. ⟨10.1016/j.jeurceramsoc.2018.04.005⟩. ⟨hal-01815090⟩