Sintered Composite for Low Temperature Coefficient of Piezoelectric Property in KNN Based Lead-Free Ceramics

We propose the design and synthesis of a polycrystalline sintered composite microstructure that leads to improved stability of piezoelectric response as a function of temperature in ( K , Na ) NbO 3 (KNN) based ceramics. The microstructure consists of matrix and island both of which have different composition and surface area. The matrix had much larger surface area and smaller orthorhombic to tetragonal transition temperature (T O-T ) than island. The composition corresponding to 0.99( K 0.48 Na 0.48 Li 0.04)( Nb 0.98 Sb 0.02) O 3-0.01 BaTiO 3 ( KNLNS-BT , T O-T ~ 33° C ) was selected as matrix while ( K 0.5 Na 0.5) NbO 3 ( KNN , T O-T ~ 206° C) was selected as island. The results show the flat electromechanical coupling factor from room temperature until ~ 300°C.