Pressure-less joining of alumina ceramics by the reaction-bonded aluminum oxide (RBAO) method

•Alumina ceramics were joined by pressure-less technique with the use of RBAO method.•Joining was performed in ambient air at 1650 ℃ for 2 h without application of pressure.•Fine-grain sized Al/Al2O3 powder mixture was used as interlayer.•Joints possess almost 100 % strength when compared with parent alumina ceramics.