3. Results and discussion
3.1. X-ray diffraction studies and microstructure analysis
The XRD patterns of representative samples from all the three sets of compositions are given in Fig. 1. It is obvious from the XRD patterns that all the compositions maintain the cubic spinel structure even after doping with various metal ions. No secondary phase is observed. This observation is also complimented by the SEM images of sintered discs as shown in Fig. 2. All the compositions have a uniform microstructure with densely packed grains. No porosity or formation of secondary phase is noticed. The homogeneous microstructure of the sintered body is a well desired property for NTC thermistors.