Dielectric properties and relaxation phenomena in the diffuse ferroelectric phase transition in K _3Li _2Nb _5O _(15) cerami

摘要

Structural and dielectric properties of Potassium Lithium Niobate polycrystalline ceramic K3Li2Nb5O15 (KLN), having the tetragonal tungsten bronze (TTB) -type structure are studied in the temperature interval 50-550 °C. Special emphasis is given to the diffuse phase transition occurring around 440 °C. Space charge polarization, relaxation phenomena and free charge conductivity have been elucidated using impedance spectroscopy technique. Argand plots have revealed a non Debye and polydispersive type relaxation. In paraelectric phase the Arrhenius activation energy E = 0.533 eV was determined. The structural and dielectric results are compared with two others TTB compounds derived from KLN family: Pb _(1.85)K _(1.15)Li _(0.15)Nb _5O _(15) (PKLN) and GdK _5Nb _5O _5 (GKN).