Sintering and Dielectric Study of Na_0.90K_0.10(Nb_0.90Mg_0.10)O_2.70F_0.30 Ferroelectric Ceramics

Abstract

Cold-pressed pellets were prepared from a powder mixture of 90 mol. % of NaNbO ₃ and 10 mol. % of KMgF ₃ . The pellets were then sintered in platinum sealed tubes at various temperatures (900°C ≤ t _sint ≤ 1100°C) during different holding times (2h ≤ θ _sint ≤ 15 h). Dielectric measurements were carried out on Na _0.90 K _0.10 (Nb _0.90 Mg _0.10 )O _2.70 F _0.30 ceramics between 100 and 800 K in a wide frequency range 20 Hz–1 GHz. At low frequencies, Na _0.90 K _0.10 (Nb _0.90 Mg _0.10 )O _2.70 F _0.30 ceramics showed a unique second order phase transition at the ferroelectric Curie temperature T _C = 540 K with a permittivity maximum of 6410. This one was confirmed by XRD analyses. In the gigahertz region the curves ε _r ′ − log f and ε _r ^″ − log f displayed a resonance phenomenon around 8× 10 ⁸ Hz. The oxyfluoride Na _0.90 K _0.10 (Nb _0.90 Mg _0.10 )O _2.70 F _0.30 could be of interest to manufacture electronic components for various devices.

Keywords:

• Na_0.90K_0.10(Nb_0.90Mg_0.10)O_2.70F_0.30
• Ferroelectric ceramics
• Dielectric properties