Microstructure and properties of Bi 2 O 3 doped 0.8(K 0.52 Na 0.48 ) NbO 3 –0.2KSr 2 Nb 5 O 15 lead‐free ceramics

The 0.8(K 0.52 Na 0.48 )NbO 3 –0.2KSr 2 Nb 5 O 15 ‐yBi 2 O 3 (0.8KNN‐0.2KSN‐yBi 2 O 3 ) lead‐free ferroelectric composite ceramics were synthesised using rod‐like KSr 2 Nb 5 O 15 (KSN) and isometric (K 0.52 Na 0.48 )NbO 3 (KNN) particles as raw material. Effects of Bi 2 O 3 doping content on microstructure, electrical, and optical properties were researched. The results indicated that the addition of Bi 2 O 3 helps to densify 0.8KNN‐0.2KSN‐y Bi 2 O 3 ceramics within limits without changing phase structure and microstructure. The dielectric constant and phase transition dispersion degree increased with the increase of Bi 2 O 3 while the dielectric loss decreased. Besides, the dielectric tunability was maintained in the range of 43.7∼51.8%, and reached its maximum when Bi 2 O 3 content was 1 wt%. In addition, the remnant polarisationPrand coercive fieldEcdecreased with the increase of Bi 2 O 3 , as well as the optical transmittance of 0.8KNN‐0.2KSN, but the transmittance of all samples was above 48%.