engleski

Aqueous sol-gel route toward selected quaternary metal oxides with single and double perovskite-type structure containing tellurium

Highly crystalline SrFe2/3Te1/3O3, Ba3Fe2TeO9 and Ba2NiTeO6 have been synthesized by using a specially developed sol-gel route methodology, reducing the time needed using solid-state routes and resulting in high reaction yield up to 75 %. These materials have been studied by X-ray powder diffraction (XRPD), scanning and transmission electron microscopy, Raman spectroscopy, dielectric and magnetic measurements. At room temperature, the crystal structure of SrFe2/3Te1/3O3 is cubic, space group Pm-3m, with a = 3.9373(2) Å, whereas Ba3Fe2TeO9 crystallizes in the hexagonal crystal system, space group P63/mmc, a = 5.7691(4) Å and c = 14.208(1) Å. The third studied perovskite Ba2NiTeO6 crystallizes in trigonal R-3m space group with a = 5.7974(4) Å and c = 28.599(2) Å. Based on structural characterization results, the obtained single and double perovskite crystallites are nearly in nanometer regime, ranging from 45 to 164 nm, building micrometer sized particles with visible well-faceted hexagonal morphology. Magnetic measurements show the onset of ferrimagnetic ordering at relatively high temperature of 667 K for the SrFe2/3Te1/3O3, whereas Ba3Fe2TeO9 and Ba2NiTeO6 show antiferromagnetic ordering below 80 and 8.6 K, respectively. The measured room temperature dielectric constants are in the range between 15 and 77.

perovskites ; tellurates ; structure ; ferrimagnetism

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