Electrical and electromechanical properties of lead–potassium–yttrium–niobate ceramics—piezoelectric applications

Tungsten bronze (TB)-type oxide ceramic Pb0.74K0.13Y0.13Nb2O6 (PKYN) has been synthesized by the standard solid state reaction method. Single phase formation, orthorhombic crystal structure was confirmed by X-ray diffraction (XRD). The substitution of Y3+ in Pb0.74K0.52Nb2O6 (PKN) decreased the unit cell volume and TC=260 °C. PKYN exhibited the remnant polarization, Pr=8.5 μC/cm2, and coercive field, Ec=28.71 kV/cm. Electrical spectroscopy studies were carried out over the temperature (35–595 °C) and frequency (45 Hz–5 MHz) ranges, and the charge carrier phenomenon, grain–grain boundary contribution and non-Debye-type relaxation were analyzed. The relaxation species are immobile charges in low temperature and oxygen vacancies at higher temperature. The theoretical values computed using the relations, ε′=ε∞+sin(n(T)π/2)(a(T)/ε0)(ωn(T)−1); σ(ω)=σdc+Aωn are fitted with the experimental one. The n and A parameters suggested that the charge carrier's couple with the soft mode and become mobile at TC. The activation enthalpy, Hm=0.38 eV, has been estimated from the hopping frequency relation ωp=ωe exp(−Hm/kBT). The piezoelectric constants Kt=35.4%, d33=69×10−12 C/N, d31=−32×10−3 mV/N, S11E=17.8 pm2/N, etc., achieved in PKYN indicate the material is interesting for transducer applications. The activation energies from different formalisms confirmed the ionic-type conduction.