Local thermal conductivity of polycrystalline AlN ceramics measured by scanning thermal microscopy and complementary scanning electron microscopy techniques

Thelocalthermalconductivityofpolycrystallinealuminumnitride(AlN)ceramicsismeasuredandimagedbyusingascanningthermalmicroscope(SThM)andcomplementaryscanningelectronmicroscope(SEM)basedtechniquesatroomtemperature.ThequantitativethermalconductivityfortheAlNsampleisgainedbyusingaSThMwithaspatialresolutionofsub-micrometerscalethroughusingthe3ωmethod.Athermalconductivityof308W/m·Kwithingrainscorrespondingtothatofhigh-puritysinglecrystalAlNisobtained.Theslightdifferencesinthermalconductionbetweentheadjacentgrainsarefoundtoresultfromcrystallographicmisorientations,asdemonstratedintheelectronbackscattereddiffraction.Amuchlowerthermalconductivityatthegrainboundaryisduetoimpuritiesanddefectsenrichedinthesesites,asindicatedbyenergydispersiveX-rayspectroscopy.