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For decades researchers work in the field of lead-freepiezoelectric ceramics to find a material that could replacelead–zirconate–titanate in piezoelectric devices. Excellentreviews on that topic are given by Rödel et al.1 or Takenakaet al.2Bi0.5Na0.5TiO3 (BNT) is one of the most promising leadfree materials for actuator applications, which was first reportedby Smolenskii et al.3 It has a perovskite type structure withrhombohedral symmetry at room temperature. The depolarizationtemperature (Td) is at 186◦C and the temperature at themaximum of the permittivity (Tm) at 335◦C.3,4 Both temperaturescan be shifted by doping. It exhibits a morphotropic phaseboundary with tetragonal compounds, such as barium titanate5and bismuth–potassium–titanate.6,7 Zhang et al.8 found a largestrain in the system Bi0.5Na0.5TiO3–BaTiO3–K0.5Na0.5NbO3(BNT–BT–KNN) which is due to a field-induced nonpolar/ferroelectric phase transition. In literature the nonpolar phaseis sometimes termed as antiferroelectric which is supported bythe shape of the polarization curves. Structural changes at Td,which were suggested by Hiruma et al.7 were not confirmed by∗ Corresponding author. Tel.: +43 316 873 8285; fax: +43 316 873 8272.E-mail address: k.reichmann@tugraz.at (K. Reichmann).Jones et al.,9 who performed Rietveld neutron powder profileanalysis of the compound Na0.5Bi0.5TiO3 over the temperatureช่วงตั้งแต่ 5 ถึงคุณ 873
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