Konstitutionsuntersuchungen im System Nd-Si-Al-O-N

In connection with the development of silicon nitride ceramics with Nd2O3/Al2O3 sintering additives the subsolidus phase relationships in parts of the the Si3N4-SiO2-AlN-Al2O3-NdN-Nd2O3 system have been studied. At subsolidus temperatures the Nd2O3-Al2O3-SiO2 system can be subdivided into 7 three- phase triangles. The measured solidus temperature is 1368 degrees C. In the Nd2O3-SiO2 system a phase with an defective apatite-type structure are formed. The experimental results show a solubility limit for alumina in the apatite structure of 5 mol-%. With increasing Al2O3 content a linear increase in the a and c lattice constants is observed. Besides the experimental studies thermodynamic calculations are performed using the computer program ThermoCalc.