High temperature stable dielectric properties of (K 0.5 Na 0.5 ) 0.985 Bi 0.015 Nb 0.99 Cu 0.01 O 3 ceramics with core–shell microstructures

New high temperature ceramic capacitors (K 0.5 Na 0.5 ) (1−x) Bi x Nb (1−2x/3) Cu 2x/3 O 3 ( x = 0–0.03) with Bi substitution for A site and Cu substitution for B site were synthesized using a solid state reaction process.