Temperature-Dependent Phase Transitions in the Lead-Free Piezoceramics (1 – – y)(Bi1/2Na1/2)TiO3–xBaTiO3y(K0.5Na0.5)NbO3 Observed by in situ Transmission Electron Microscopy and Dielectric Measurements


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Lead-free piezoelectric (1 – – y)(Bi1/2Na1/2)TiO3xBaTiO3y(K0.5Na0.5)NbO3 (BNT–BT–KNN) ceramics were examined in situ under increasing temperature in the transmission electron microscope. Changing superstructure reflections indicate a transition from rhombohedral to tetragonal to cubic phase with broad coexistence regions. The additional evolution of the microstructure in combination with dielectric measurements leads to a model of two relaxor-type phase evolutions with temperature.