Low Temperature Phase Transformation Study in the Al sub(2)O3-Y sub(2)O sub(3 )-Nb sub(2)O sub(5) System

The mechanical properties and creep resistance of the Al sub(2)O sub(3) have been improved with the use of other oxide ceramics, among these the Y sub(3)Al sub(5)O sub(12) (YAG - "yttrium aluminum garnet"), to obtain the Al sub(2)O sub(3)-YAG composite. The aim of this work is to study the effect of addition of Nb sub(2)O sub(5) at low sintering temperatures of the composite, starting from the eutectic composition Al sub(2)O sub(3)-Y sub(2) O sub(3). In this work, the compositions were produced by powder mixtures of Al sub(2)O sub(3)-Y sub(2)O sub(3) and Al sub(2)O sub(3)-Y sub(2) O sub(3)-Nb sub(2)O sub(5) using high energy ball milling. The green bodies were pressed at 70 MPa and sintered at 1000, 1100, 1200 and 1300[degrees]C for 2 h. The materials were characterized by shrinkage and X-Ray Diffraction (XRD) using the Rietveld method. The presence of Nb sub(2)O sub(5) does not show any improve neither for the YAG phase formation nor for the shrinkage of the sintered samples in the temperature range studied.