X-ray analysis of phase coexistence and electric poling processing in alkaline niobate-based compositions

The phase diagram of K0.5Na0.5NbO3–Bi1/2Na1/2TiO3

“…Good piezoelectric properties are observed for solid solutions within a transition region of the phase diagrams known as the morphotropic phase boundary (MPB; Jaffe et al, 1971), where the crystal structure changes suddenly with composition. However, KNN often exhibits a diffuse polymorphic phase transition between orthorhombic and tetragonal phases when the temperature is lowered to near room temperature (Fu et al, 2010;Liu et al, 2012), which results in a polymorphic phase boundary (PPB). Unlike an MPB located in a narrow composition region and almost temperature independent, as in the PZT system, the position of the PPB in most KNN solid solutions shifts gradually and continuously to lower temperatures (Zhang et al, 2007;Dai et al, 2007).…”

Structure and electrical properties of K0.5Na0.5Nb0.94−Sb0.06Sn O3 lead-free piezoelectric ceramics

“…Recently, the studies of alkali metal niobate-based piezoelectric ceramics are mainly concentrated in the potassium sodium niobate, which because that (K 0.5 Na 0.5 )NbO 3 (KNN) piezoelectric ceramics possess low theoretical density, high Curie temperature, at the same time with good piezoelectric properties and mechanical properties [12][13][14][15][16][17]. However, pure KNN piezoelectric ceramic sintered by the traditional ceramic preparation process is difficult to obtain dense ceramic body [16][17][18][19][20].…”

“…However, pure KNN piezoelectric ceramic sintered by the traditional ceramic preparation process is difficult to obtain dense ceramic body [16][17][18][19][20]. These difficulties are concerned with a narrow temperature range of sintering, the volatilization of K and Na, a poling barrier result from high loss tangent and the evolution of secondary phases [21][22][23].…”

Evaluating the polymorphic phase transition in calcium-doped Ba(Zr0.05Ti0.95)O3: a lead-free piezoelectric ceramic

“…Near the MPB, the energy barriers of the two phases are close to each other, making it easy for polarization to jump from one state to another when an external field is applied. It has been realized (Chang et al, 2009;Fu et al, 2010) that coexistence of ferroelectric phases can also be achieved near room temperature in systems having a polymorphic phase transition (PPT). It is known that pure BaTiO 3 undergoes polymorphic phase transitions in the temperature range 200-405 K (Jaffe et al, 1971;Lines & Glass, 1977;Clarke, 1976).…”