Environmentally　friendly　potassium　sodium　niobate　(KNN)-based　ceramics　are　potential　electronic　functional　materials　due　to　multiphase　coexistence.　Aliovalent　doping　on　the　A-site　with　different　ions　plays　a　key　role　in　phase　boundary　engineering.　However,　the　difference　of　contribution　to　the　phase　boundary　from　various　A-site　dopants　is　not　clear　in　multielement　high　performance　KNN-based　ceramics.　Herein,　the　individual　contribution　to　phase　structure　and　comparison　of　typical　aliovalent　ions　(Bi3+　and　Ca2+)　on　the　A-site,　are　considered　in　terms　of　influence　on　electrical　properties.　Within　a　maintained　rhombohedral-orthorhombic-tetragonal　(R-O-T)　phase　boundary　at　room　temperature,　both　phase　transition　temperatures　for　rhombohedral-orthorhombic　(TR-O)　and　orthorhombic-tetragonal　(TO-T)　gradually　enhance　with　increasing　Ca2+　and　decreasing　Bi3+,　resulting　in　elevating　R　phase　and　reducing　T　phase.　This　phenomenon　indicates　that　the　contribution　of　Ca2+　to　increase　TR-O　is　stronger　than　that　from　Bi3+,　while　the　effect　on　decreasing　TO-T　from　Ca2+　is　weaker　with　respect　to　Bi3+　during　phase　boundary　formation.　The　enhancement　of　TR-O　and　TO-T　is　due　to　the　lower　electronegativity　of　Ca2+　than　Bi3+　which　benefits　an　R　phase　with　high　ionicity.　There　is　only　a　small　change　in　TC　and　diffusion　degree　when　Bi3+　is　replaced　by　Ca2+,　because　of　the　similar　substitution　of　Bi3+　and　Ca2+　on　the　A-site.　Meanwhile,　enhanced　O　vacancies　are　due　to　the　lower　valence　of　Ca2+　than　that　of　Bi3+.　Then,　electrical　properties　including　ferroelectricity,　piezoelectricity　and　strain,　retain　high　values　originating　from　the　maintained　R-O-T　phase　boundary.　Moreover,　improved　stability　of　piezoelectricity　and　strain　under　changing　temperature,　are　achieved　based　on　enhanced　TO-T.　Thus,　this　work　provides　an　effective　method　to　further　optimize　multiphase　structures　via　appropriate　doping　in　KNN-based　ceramics.　©　2022　The　Royal　Society　of　Chemistry.