3Y-ZrO2/BN　ceramic　composites　with　nano-sized　BN　dispersoids　ranging　from　0　to　30　vol.%　were　successfully　fabricated　by　hot-pressing　turbostratic　BN　(t-BN)　coating　3Y-ZrO2　powders,　which　were　prepared　via　in　situ　reaction　between　boric　acid　and　urea　on　the　surface　of　3Y-ZrO2　particles　in　nitrogen　gas.　XRD　analysis　and　TEM　observations　revealed　that　the　nano-sized　turbostratic　and　hexagonal　BN　(t/h-BN)　particulates　were　dominantly　dispersed　at　ZrO2　grain　boundaries.　Vickers　hardness　of　materials　decreased　directly　with　an　increase　of　BN　content.　The　fracture　strength　and　the　fracture　toughness　were　considerably　improved,　in　comparison　to　corresponding　3Y-ZrO2/BN　microcomposites.　The　nanocomposites　with　BN　content　more　than　20　vol.%　were　ready　for　machining.　The　preliminary　information　on　the　relationship　between　microstructures　and　properties　are　provided.　(c)　2005　Elsevier　B.V.　All　rights　reserved.