Processing issues and their influence in the magnetoelectric performance of (K,Na)NbO3/CoFe2O4-based layered composites

Abstract

Low temperature processing of environmentally-friendly (K,Na)NbO 3and CoFe 2 O 4-based layered composites has been accomplished by hot pressing, and their electrical, piezoelectric and magnetoelectric properties have been characterized. High quality composite three-layer CoFe 2 O 4 /K 0.5 Na 0.5 NbO 3 /CoFe 2 O 4 structures with defect-free interfaces have been obtained by hot pressing at only 1000 o C, when highly reactive CoFe 2 O 4 powders obtained by Pechini are used. Negligible chemical reactions at, and interdiffusion across interfaces take place during the low temperature processing, while alkali volatilization is also minimized. Dense, crack-free

Selection and Optimization of a K0.5Na0.5NbO3-Based Material for Environmentally-Friendly Magnetoelectric Composites

“…Note that these two compositions were the only ones for which said temperature was below the onset one for alkali volatilization, and thus, below the temperature used for sintering (1110 • C). Additionally, all ceramic materials showed grains with core-shell structure, which is frequently observed in LKNNT materials [31,34,37,47] when conventional solid state synthesis from alkaline carbonates and Ta and Nb oxides is carried out. It has been associated with compositional inhomogeneities, so that Nb-and K-rich cores are surrounded by Ta-rich shells [31].…”

“…KNN-based materials have already been investigated as piezoelectric components in magnetoelectric layered composites, and ME coefficients close to those of PZT-containing materials have been obtained [36][37][38]. Compositions with high piezoelectric coefficients were selected in these works.…”

Enhanced piezomagnetic coefficient of cobalt ferrite ceramics by Ga and Mn doping for magnetoelectric applications

“…Note that analytical calculations in this work refer to bilayer composites, and it is well known that multilayer configurations (three layers or more) show larger ME responses. 14,52 Besides, ME coupling in 1-3 composite structures is considerably stronger than in laminated ones because response arises from d 33 and q 11 instead of d 31 and q 11 + q 21 ; 15 and, d 33 and q 11 are known to be greater compared than d 31 and q 11 + q 21 , respectively. In fact, the large q 11 value showed by the CFG15 composition suggest it to be an excellent candidate for magnetostrictive phase in 1-3 ME composites.…”

“…Magnetic metallic alloys or spinel oxides are used for the former component, while ferroelectric polymers or perovskite phases are preferred for the latter one. 2,[4][5][6][7][8] Interest in cofired ceramic composites has grown due to their low cost, easy manufacturing, possibility of co-sintering the magnetostrictive and piezoelectric oxide phases, and high electrical resistivity when compared to metallic alloys as Metglas or Terfenol-D. [9][10][11][12][13][14] Among magnetostrictive phases, CoF e 2 O 4 (CFO) stands out because of its very high magnetostriction (λ). 15 However, studies in ME composites formed by CFO-based compositions mostly resulted in ME coefficients lower than those using N iF e 2 O 4 -based magnetostrictive phases.…”

Environmentally-friendly magnetoelectric ceramic multilayer composites by water-based tape casting

“…Note that substitution of N iF e 2 O 4 by a nickel-free alternative magnetostrictive oxide should also be carried out, if an utter environmentally-friendly material technology is targeted [29].…”