Temperature Evolution of Physical Properties of BaTi0.9(Nb0.5Yb0.5)0.1O3 Lead-Free Ceramic

BaTi0.9(Nb0.5Yb0.5)(0.1)O-3 lead-free ceramic was prepared by a solid-state reaction method. The structure of BaTi0.9(Nb0.5Yb0.5)(0.1)O-3 has been characterized by means of x-ray diffraction, showing the coexistence of cubic (31.1%) and tetragonal (68.9%) phases at room temperature. Dielectric spectroscopy shows that BaTi0.9(Nb0.5Yb0.5)(0.1)O-3 composition sintered at 1380A degrees C exhibits a relaxor behavior with a weak diffuse phase transition obeying a Lorentz-type quadratic relationship. The ferroelectric-paraelectric phase transition T (C) decreased from 420 K for BaTiO3 to 284 K for BaTi0.9(Nb0.5Yb0.5)(0.1)O-3. The dielectric loss of this ceramic was < 0.09 over a wide temperature range (< 400 K). The temperature behavior of the main piezoelectric parameters, such as the piezoelectric coefficient d (31) and the electromechanical coupling factor k (p), was investigated. d (31) sets a maximum about 32.5 pC/N at temperature of 220 K. Nevertheless, k (p) undergoes more or less important changes between 120 K and 200 K. Over 200 K, k (p) degrades very rapidly due to the depoling effect deduced from the hysterisis measurements. Dielectric and structural properties of BaTi0.9(Nb0.5Yb0.5)(0.1)O-3 were confirmed by Raman spectroscopy.