Data di Pubblicazione:
2008
Citazione:
Defect chemistry and dielectric properties of Yb3+:CaTiO3 perovskite / M. BASSOLI, M.T. BUSCAGLIA, C. BOTTINO, V. BUSCAGLIA, M. MOLINARI, F. MAGLIA, G. PARRAVICINI, M. DAPIAGGI. - In: JOURNAL OF APPLIED PHYSICS. - ISSN 0021-8979. - 103:1(2008), pp. 014104.014104.1-014104.014104.10. [10.1063/1.2828149]
Abstract:
The defect chemistry of Yb3+ :CaTiO3 solid solutions has been investigated both theoretically and
experimentally. Three different incorporation mechanisms with similar solution energy were
predicted for Yb3+ by atomistic simulation: i Ca site substitution with Ca vacancy compensation;
ii Ti site substitution with O vacancy compensation; iii simultaneous substitution at both Ca and
Ti sites with self-compensation. X-ray diffraction and scanning electron microscopy results strongly
support the possibility to realize the above defect chemistries in CaTiO3 by changing the Ca/Ti ratio
to force Yb3+ on the Ca site Ca/Ti 1 , on Ti site Ca/Ti 1 , or on both sites Ca/Ti=1
according to the calculations. The temperature dependence of the relative dielectric constant
102–105 Hz of ceramics corresponding to predominant Yb substitution either at the Ca site or the
Ti site is qualitatively similar to that of undoped CaTiO3. The Curie-Weiss temperature is shifted to
more negative values in comparison to CaTiO3, suggesting that the compositions Ca1−3/2xYbxTiO3
and CaYbxTi1−xO3 are further driven away from the ferroelectric instability. In contrast, the
dielectric properties 102–105 Hz of ceramics corresponding to Ca1−x/2YbxTi1−x/2O3 are radically
different. The relative dielectric constant is increased of about one order of magnitude 2200 at
30 K , is almost independent of temperature, with a maximum variation of 20% in range of
20–300 K, and shows frequency dispersion above 150 K. The loss tangent at 20–300 K is 5% for
frequencies 1 kHz. The possible mechanism for the observed dielectric behavior is discussed.
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
M. Bassoli, M.T. Buscaglia, C. Bottino, V. Buscaglia, M. Molinari, F. Maglia, G. Parravicini, M. Dapiaggi
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