Development　of　miniaturized　magnet-associated　devices　operated　at　elevated　temperatures　requires　that　the　2:17-type　Sm(Co,　M)(z)　(M　=　Fe,　Cu,　Zr)　permanent　magnets　have　large　magnetic　energy　product　and　high　coercivity.　Raising　iron　content　is　essential　to　enlarge　the　energy　product,　however　it　leads　to　serious　deterioration　in　coercivity　(H-cj)　and　squareness　factor　(SF).　In　order　to　uncover　the　underlying　microstructural　origins,　here　we　performed　a　comparative　study　between　two　nanocell　structured　Sm(Co0.68Fe0.22Cu0.07Zr0.03)(7.5)　magnets　with　different　magnetic　properties.　We　found　that　the　nanoscale　interfacial　defects,　including　the　retained　phase　at　the　grain　edges　and　the　intermediate　rhombohedral　phase　(2:17R＇)　at　the　cell　edges,　act　as　extra　defects　that　are　detrimental　to　the　coercivity　as　well　as　the　squareness,　besides　the　formerly-reported　incomplete　cell　walls　and　discontinuous　platelets.　These　microstructural　defects　build　up　inhomogeneous　pinning　sites,　at　the　interfaces　between　the　cell　walls　and　the　cell　interiors,　and　at　the　intersections　of　the　cell　walls　and　the　Zr-rich　platelets.　The　comparative　results　show　that　the　magnet　with　H-cj　=　34.39　kOe　and　SF=　62.08%　contains　much　less　microstructural　defects　than　the　one　with　H-cj　=　24.42　kOe　and　SF　=　47.08%.　Our　work　highlights　the　importance　of　reducing　microstructural　defects　for　achieving　high　coercivity　and　large　squareness　in　the　iron-rich　Sm(Co,　M)(z)　permanent　magnets.　(C)　2019　Elsevier　B.V.　All　rights　reserved.