Tungsten bronzes framework as a glasslike host for transition cations: the case of Ba6Zr2Ta8O30

Structural, microstructural, and spectroscopic properties of Ba6Zr2Ta8O30 (BZT) and Ba6Zr1.94M0.06Ta8O30 (M = Ni, Co, Fe, Mn, Cr) related doped compounds are reported. The distribution of Zr, Ta, and M dopant ions on the cationic sites and the M valence states are discussed on the basis of the results obtained by the application of the Rietveld method on X-ray powder diffraction (XRPD) patterns and by electron paramagnetic resonance. The micro-Raman spectra of pure and doped BZT, reported and discussed for the first time, confirm the capability of the lattice to host transition cations in a glasslike matrix. The particle size effects of the samples are investigated by analyzing XRPD line broadening and scanning electron microscopy observations. Comparisons with the isostructural pure and doped Ba6Ti2Nb8O30 compounds are also reported.