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.