Role of BiScO3 in phase structure and electrical properties of potassium sodium niobate ternary materials

In this work, we mainly studied the effects of BiScO3 contents on the phase structure and electrical properties of lead-free (K,Na)NbO3-based ternary ceramics, and the material system of (0.97-x)K0.40Na0.60NbO3-xBiScO3 -0.03Bi0.5(Na0.6K0.3Li0.1)0.5HfO3 was prepared by the normal sintering method. The rhombohedral-tetragonal (R-T) phase boundary could be tuned in the ceramics by controlling BiScO3 contents. When the compositions approach the R-T phase boundary, the ceramics possess the enhancement of dielectric, ferroelectric and piezoelectric properties. The ceramics with x = 1.2% exhibited an excellent electrical behavior of d33 = 362 pC/N, kp∼0.42, Pr∼19.9 μC/cm2, εr∼1671, and tan δ∼0.02, which is assigned to the involvement of R-T phase boundary. Moreover, a high Curie temperature (TC) of ∼315 °C can be maintained even if the BiScO3 contents increase because of the addition of both BiScO3 and Li. As a result, the ceramics with x = 1.2% had both a large d33 and a high TC, showing that such a lead-free piezoelectric ternary system is suitable to the high-temperature applications.