Microstructure, electrical properties, and electric field-induced phase transitions in NaNbO₃-LiTaO₃lead-free ceramics

Lead-free ceramics (1-x)NaNbO3-xLiTaO3were synthesized by an ordinary solid-state reaction method. Rietveld analysis reveals that the crystal structure changes from one orthorhombic phase with Pbcm space group to another orthorhombic phase with P2221space group when increasing x. The morphotropic phase boundary between two different orthorhombic symmetries is formed at 0.14 < x < 0.18. Excess LiTaO3causes an abnormal grain growth behavior. The pure NaNbO3presents four current peaks in the I-E loop, indicating electric-field-induced transitions. A low LiTaO3doping induces ferroelectricity in the initially antiferroelectric (AFE) NaNbO3. Enhanced ferroelectricity is obtained at x = 0.02-0.12. The addition of LiTaO3makes the ceramics undergo a transition from an antiferroelectricity dominant to a ferroelectricity dominant phase state. The optimum d33, kp, Qm, and Prvalues of 46 pC/N, 18.3%, 1333, and 27.1 μC cm-2are obtained when x equals 0.12, and the ceramic exhibits good temperature stability because of its high TC. KGaA, Weinheim.