A new family of ferroelectric materials: Me2Nb4O11 (Me = Na and Ag)

Abstract

Ceramic samples of Me₂Nb₄O₁₁ (Me = Na and Ag) show ferroelectricity with a permittivity maximum of ∼150 at T_C ≈ 110 °C and a possible second transition below room temperature. Hysteresis loops of Na₂Nb₄O₁₁ at room temperature show remanent polarisation ∼2 μC cm⁻² at 30 kV cm⁻¹. The existence of spontaneous polarisation is not compatible with the centrosymmetric space group C2/c originally reported. The crystal structures were successfully refined in the non-centrosymmetric space group Cc.