Electrical and electromechanical studies in ferroelectric Gd3+modified lead potassium niobate ceramics

Abstract

The change in dielectric constant relaxation time over temperature (35–590 °C) and frequency (45 Hz–5 MHz) in ceramics of Pb 0.77 K 0.115 Gd 0.115 Nb 2 O 6 (PKGN, T c = 340 °c) has been studied. Powder X-ray diffraction revealed the single-phase formation with orthorhombic crystal structure. The P-E hysteresis loop parameters are P s = 21.77 μ C/cm 2 , P r = 17.09 μ C/cm 2 , E c = 11.86 kV/cm; the piezoelectric constants, K p = 31.7%, K t = 47%, d 33 = 115 × 10 −12 C/N, d 31 = −41 × 10 −12 C/N, are determined in the material and some transducer applications are discussed. Cole-Cole (Z ll vs. Z l ) plots showed a non-Debye type relaxation. Conductivity obeyed Jonscher’s universal power law, σ = σ 0 + A ω n . The theoretical values of e l and σ are computed using the parameters ‘ A ( T )’ and ‘ n ( T )’ (0 1) and are well fitted with the experimental data. The hopping ion frequency ( ω p ) and charge carrier concentration ( K l ) have been analyzed using Almond-West formalism. The dielectric relaxation processes are associated with localized oxygen vacancies conduction at high frequency region. A long-range conductivity by Gd 3+ ions is found to be predominant at low frequency region. The activation energies from impedance and modulus formalisms revealed the ionic type conduction in PKGN.