Lead-free piezoelectric ceramics in the (1 − x)Sr2NaNb5O15–xCa2NaNb5O15 (0.05 ≤ x ≤ 0.35) system

Abstract

The study investigating the electrical properties of dense lead-free piezoelectric ceramics in the (1 − x)Sr₂NaNb₅O₁₅–xCa₂NaNb₅O₁₅ (SCNN) system with x ranging from 0.05 to 0.35 is reported here. X-Ray diffraction patterns all showed a single tetragonal tungsten bronze phase, peak broadening being seen on increasing the Ca content. The lattice constant calculation indicated distortion and shrinkage of the crystal structure with Ca substitution. Dielectric spectra of each composition displayed two dielectric anomalies and diffusive phase transitions. The Curie temperature, T_c, shifted upward whereas the relative permittivity at T_c declined monotonically as the Ca content increased. Ferroelectric and piezoelectric properties of SCNN greatly depended on the Ca content. The composition with x = 0.15 exhibited the greatest polarization with P_r = 3.0 μC cm⁻² and piezoelectric constant of d₃₃ = 96 pC N⁻¹, whereas the compositions with x = 0.30 and 0.35 almost lost their ferroelectricity and piezoelectricity. This study apparently indicates that lead-free SCNN piezoelectric ceramics have potential for electromechanical applications.