24.12.2010

Solid State Sciences
Volume 12, Issue 12, December 2010, Pages 1970-1976

Ba₃M^IIITiM^VO₉ (M^III = Fe, Ga, Y, Lu; M^V = Nb, Ta, Sb) perovskite oxides: Synthesis, structure and dielectric properties

Joby E. Joy^a, Eric Atamanik^b, Rohini Mani^a, Abanti Nag^a, R.M. Tiwari^a, V. Thangadurai^b and J. Gopalakrishnan^a^,^,

^a Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India

^b Department of Chemistry, University of Calgary, 2500 University Dr NW, Calgary, Alberta T2N 1N4, Canada

Received 20 August 2009;

revised 2 June 2010;

accepted 9 August 2010.

Available online 17 August 2010.

Abstract

We describe the synthesis, structures and dielectric properties of new perovskite oxides of the formula, Ba₃M^IIITiM^VO₉, for M^III = Fe, Ga, Y, Lu and M^V = Nb, Ta, Sb. While M^V = Nb and Ta oxides adopt disordered/partially ordered 3C perovskite structures where M^III/Ti/M^V metal-oxygen octahedra are corner-connected, the M^V = Sb oxides show a distinct preference for the 6H structure, where Sb^V/Ti^IV metal-oxygen octahedra share a common face forming (Sb,Ti)O₉ dimers that are corner-connected to the M^IIIO₆ octahedra. The preference of antimony oxides (Sb^V:4d¹⁰) for the 6H structure – which arises from a special Sb^V–O chemical bonding that tends to avoid linear Sb–O–Sb linkages unlike Nb^V/Ta^V:d⁰ atoms which prefer not, vert, similar 180° Nb/Ta–O–Nb/Ta linkages – is consistent with the crystal chemistry of M^V–O oxides in general. The dielectric properties reveal a significant difference among M^III members. All the oxides with the 3C structure excepting those with M^III = Fe show a normal low loss dielectric behaviour with ε = 20–60 in the temperature range 50–400 °C; the M^III = Fe members with this structure (M^V = Nb, Ta) display a relaxor-like ferroelectric behaviour with large ε values at frequencies ≤1 MHz (50–500 °C).

Graphical abstract

Investigation of structure and dielectric properties of Ba₃M^IIITiM^VO₉ oxides brings out the role of various M^III and M^V atoms for the formation of 3C and 6H perovskites and their dielectric properties.