Rhombohedral-tetragonal phase coexistence and piezoelectric properties based on potassium-sodium niobate ternary system

In this work, the rhombohedral-tetragonal (R-T) phase coexistence has been designed using the ternary system consisting of (0.99-x)K0.48Na0.52NbO3-0.01B(0.5)Na(0.5)TiO(3) xBi(0.5)(Na0.7K0.2K0.2Li0.1)(0.5)ZrO3. The R-T phase coexistence zone was identified in the ceramics with 0.03 <= x < 0.05, as confirmed by the phase diagram derived from both temperature-dependent dielectric constant and the X-ray diffraction patterns. The relationship between R and T phase boundary and their electrical properties is investigated. For the compositions near the R-T phase boundary, the ceramics show the enhanced dielectric, ferroelectric, and piezoelectric properties. The ceramic with x = 0.035 has an optimum electrical behavior (e.g., d33 similar to 310 pC/N, kp similar to 0.45, P-r similar to 23.4 mu C/cm(2), E-c similar to 17.4 kV/cm, epsilon(r) similar to 1249, tan delta similar to 0.025, and T-c similar to 338 degrees C). In addition, the good temperature and thermal stability of ferroelectric and piezoelectric properties were shown in the ceramic with x = 0.035. Underlying physical mechanisms for enhanced electrical properties were addressed. As a result, the design of ternary system can effectively promote the piezoelectricity of potassium-sodium niobate materials. (C) 2014 Elsevier B.V. All rights reserved.