Mechanical　characterization　of　dielectric　ceramics,　which　have　drawn　extensive　attention　in　wireless　communication,　remains　challenging.　The　micromechanical　properties　with　the　microstructures　of　dielectric　ceramic　BaO–Sm2O3–5TiO2　(BST)　were　assessed　by　nanoindentation,　microhardness,　and　microscratch　tests　under　different　indenters,　along　with　the　X-ray　diffraction　(XRD),　scanning　electron　microscopy　(SEM),　and　Raman　spectroscopy.　Accurate　determination　of　elastic　modulus　(EIT)　(i.e.,　260　GPa)　and　indentation　hardness　(HIT)　(i.e.,　16.2　GPa)　of　brittle　BST　ceramic　by　the　instrumented　indentation　technique　requires　low　loads　with　little　indentation-induced　damage.　The　elastic　modulus　and　indentation　hardness　were　analyzed　by　different　methodologies　such　as　energy-based　approach,　displacement-based　approach,　and　elastic　recovery　of　Knoop　imprint.　Consistent　values　(about　3.1　MPa·m1/2)　of　fracture　toughness　(KC)　of　BST　ceramic　were　obtained　by　different　methods　such　as　the　Vickers　indenter-induced　cracking　method,　energy-based　nanoindentation　approaches,　and　linear　elastic　fracture　mechanics　(LEFM)-based　scratch　approach　with　a　spherical　indenter,　demonstrating　successful　applications　of　indentation　and　scratch　methods　in　characterizing　fracture　properties　of　brittle　solids.　The　deterioration　of　elastic　modulus　or　indentation　hardness　with　the　increase　in　indentation　load　(F)　is　caused　by　indentation-induced　damage　and　can　be　used　to　determine　the　fracture　toughness　of　material　by　energy-based　nanoindentation　approaches,　and　the　critical　void　volume　fraction　(f*)　is　0.27　(or　0.18)　if　elastic　modulus　(or　indentation　hardness)　of　the　brittle　BST　ceramic　is　used.　The　fracture　work　at　the　critical　load　corresponding　to　the　initial　decrease　in　elastic　modulus　or　indentation　hardness　can　also　be　used　to　assess　the　fracture　toughness　of　brittle　solids,　opening　new　venues　of　the　application　of　nanoindentation　test　as　a　means　to　characterize　the　fracture　toughness　of　brittle　ceramics.　©　The　Author(s)　2023.