Novel Incipient Ferroelectrics Based on Ba4MNbxTa10-xO30 where M = Zn, Mg, Co, Ni

We report on structural, dielectric, magnetic and Raman data of the title compounds. Analysis of the single crystal diffraction data reveals that the ground state of the title compounds can be characterized within the Cm space group. The Ba4MTa10O30 compounds show typical features of incipient ferroelectrics, i.e., their dielectric constant gradually increases on cooling and levels off or slightly decreases below 10 K. Nb solubility limit, x, for Ba4MNbxTa10-xO30 compositions equilibrated at 1450-1600 degrees C was determined by powder XRD and by electron probe microanalysis. Substitution of Nb for Ta leads to the low-temperature dielectric anomaly having a relaxor-type signature. The Co- and Ni-based compounds show paramagnetic behavior in the 2-300 K range with no indication of the magnetic long-range order.