Experimental study on microstructure development of binary system Zn-O-Nb2O5 sintered at 1100 deg C-1400 deg C

In order to find effective (simple) varistor, in this work effect of Nb2O5 addition on microstructure development and it's mechanism was studied experimentally. The study was conducted by sintering Zn-O added with 0-1% mole Nb2O5 at 1100oC-1400oC in air for 1 hour and analyzing the sintered pellets using optical and electromicroscope (SEM) and x-ray diffractometer. The x-ray diffraction analysis showed that in Nb2O5 added -ZnO (Zn-O-Nb2O5) pellets sintered at 1100oC-1400oC, second phase of Zn3Nb2O8 existed. On the other hand, the metallographic analysis showed that at sintering temperature of 1100oC-1400oC, grain size of Zn-O-Nb2O5 pellets increased with increasing of Nb2O5, however, the grain size decreased again after the concentration of Nb2O5 exceeding certain value. From this data it was know also, that there was solid solution area in Zn-O-Nb2O5 phase diagram. At sintering temperature ≥ 1300oC, there was liquid phase sintering that make grains become rounded