A study of the microstructure and thermo-electrical properties of Bi2O3 ceramics co-doped with rare earth oxides

Bi2O3-based solid solutions containing rare earth oxides (Er2O3, Eu2O3, Gd2O3, and Ho2O3) have been produced through solid state reactions under atmospheric conditions. To study the impact of dopant concentration on phase structure and conductivity, the total dopant percentage is increased from 20 to 80%. According to the XRD patterns, only samples A2 (10%Er: 10%Eu: 10%Gd: 05%Ho) and B1 (05%Er: 05%Eu: 05%Gd: 10%Ho) are stabilized by the cubic delta-phase, indicating a homogeneous phase. During heating, the DTA curve of sample A1 (05%Er: 05%Eu: 05%Gd: 05%Ho) displays an endothermic peak at around 729 degrees C, indicating the phase transition from alpha-phase to delta-phase. The temperature dependent conductivity graph of the same sample confirm the phase transition due to a sudden increase in conductivity at that temperature value. At 750 degrees C, sample A2 has the highest conductivity and the lowest activation energy, with values of 0.0144 S.cm-1 and 0.48 eV, respectively. FE-SEM images indicate that the grain sizes are not uniform and decreases as the dopant concentration increases.

Automated summary

Bi2O3-based solid solutions doped with rare earth oxides (Er2O3, Eu2O3, Gd2O3, and Ho2O3) were synthesized through solid state reactions at atmospheric conditions. Increasing the dopant concentration from 20% to 80%, the impact on phase structure and conductivity was studied. XRD patterns revealed that only samples A2 (10%Er: 10%Eu: 10%Gd: 05%Ho) and B1 (05%Er: 05%Eu: 05%Gd: 10%Ho) exhibited stabilized cubic delta-phase, indicating homogeneity. Heating analysis showed that sample A1 (05%Er: 05%Eu: 05%Gd: 05%Ho) underwent a phase transition from alpha-phase to delta-phase at approximately 729 degrees C, as evidenced by an endothermic peak in DTA curve. The conductivity graph of the same sample displayed a sudden increase in conductivity at that temperature value, confirming the phase transition. At 750 degrees C, sample A2 exhibited the highest conductivity (0.0144 S.cm-1) and the lowest activation energy (0.48 eV), while the grain sizes became increasingly non-uniform as dopant concentration increased based on FE-SEM images.