Guenther, A.; Hochleitner, R.; Schmidbauer, E.; SchoettlerHimmel, A.; Volk, M.
(2019):
Influence of JahnTeller active Mn3+ ions on electrical and dielectric properties, thermopower and Mossbauer spectra of rutiletype Fe1xMnxNbTiO6 (0 <= x <= 0.9).
In: Journal of Physics and Chemistry of Solids, Vol. 124: pp. 343351

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Abstract
Various electrical and dielectric properties were measured on rutiletype compositions Fe1xMnxNbTiO6 (0 <= x <= 0.9) between approximate to 100 K and 750 K using impedance spectroscopy. DC conductivity sigma(DC) shows Arrhenius behavior for the bulk above room temperature (RT) for all x values. Starting from x = 0, there is a considerable change in activation energy EA and sigma(DC)(300 K) between x = 0.1 and 0.2 with increase from EA approximate to 0.30.6 eV, accompanied by a fall in sigma(DC) (300 K) from approximate to 10(4) to 10(8)ohm(l) cm(1);for x > 0.2 no considerable further variation with rising x is established. For x <= 0.1, below RT Mott's variable range hopping T1/4 law is obeyed for up sigma(DC). The known relaxortype behavior of the dielectric constant epsilon' for x = 0 with very high peaks at 500600 K for low frequencies (163 Hz6 kHz) changes with rising x to consecutively lower values in epsilon' with disappearance of the peaks and with the largest values at the highest applied temperatures;the relaxortype behavior can originate from a combination of bulk, grain boundary and sampleelectrode effects. Below RT, a dramatic decrease in epsilon' is noted for low x values, resulting finally at approximate to 100 K for compositions of x in the bulk value of epsilon' < 15. The thermopower above RT is negative, hence ntype conduction occurs and charge transport is attributed to small polaron hopping. Fe57 Mossbauer parameters exhibit some irregularities between x = 0.05 and 0.2, ascribed predominantly to the influence of local distortions by JahnTeller active Mn3+ ions.