Zr and Mo doped YMnO3: The role of dopants on the structural, microstructural, chemical state, and dielectric properties

The effect of Zr and Mo doping on the structural, microstructural, oxidation state, and dielectric properties of YMnO3 were investigated. The XRD studies show a low Zr and Mo solubility (-4 and 8%) in the YMnO3 matrix. In addition, it is found that the Mo doping induces a phase transition at room temperature from noncentrosymmetric (P6(3)cm space group) to centrosymmetric (P63/mmc space group) hexagonal structure; such a phase transition stabilizes above 10% of Mo doping. The transition from P63cm to P6(3)/mmc involves an increase of the volume cell. SEM analysis shows that while Zr doping does not produce significant changes in morphology and grain size, notable changes are observed in morphology and grain size with Mo doping. The chemical oxidation state, analyzed by XPS, identified two types of manganese species in the YMnO3 structure, Mn+3 and Mn+4. The presence of Zr+4 is confirmed in YMn1-xZrxO3 samples. Contrary to that, the Mo+6 is identified in YMn1-xMoxO(3) samples. In addition, it is found that the Mo doping decreases the Mn+4 oxidation state in the crystal structure. The dielectric spectra show a relaxor behavior occurring between 375 and 550 K, which is discussed regarding the interstitial oxygen absorption mechanism.