Crystal Structure and Dielectric Properties of LaYbO3 |
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| Authors: | Antonio Feteira Lisa J Gillie Ralf Elsebrock Derek C Sinclair |
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| Affiliation: | Ceramics and Composites Laboratory, Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Sheffield, S1 3JD, U.K.; Department of Chemical &Biological Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, U.K.; Institute of Electroceramic Materials, Research Centre Jülich, 52425 Jülich, Germany |
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| Abstract: | The crystal structure and dielectric properties of LaYbO3 ceramics prepared by the mixed-oxide route have been investigated. Rietveld refinements performed on X-ray and neutron diffraction data show the room-temperature structure to be best described by the orthorhombic Pnma space group a =6.02628(9) Å, b =8.39857(11) Å, and c =5.82717(7) Å; Z =4, and theoretical density, D x =8.1 g/cm3] in agreement with electron diffraction experiments. LaYbO3 ceramics fired at 1600°C for 4 h attain ～97% of D x and their microstructures consist of randomly distributed equiaxed grains with an average size of ～8 μm. Conventional transmission electron microscopy shows densification to occur in the absence of a liquid phase and reveals domain-free grains. The relative permittivity, ?r, of LaYbO3 ceramics at radio frequencies is ～26 in the range ～10–300 K; however, a small dielectric anomaly is detected at ～15 K. At room temperature and microwave frequencies, LaYbO3 ceramics exhibit ?r～26, Q × f r～20 613 GHz (at 7 GHz), and τf～?22 ppm/K. Q × f r show complex subambient behavior, decreasing from a plateau value of ～20 000 GHz between ～300 and 200 K to a second plateau value of ～6000 GHz at ～90 K before decreasing to <1000 GHz at ～10 K. The large decrease in Q × f r at low temperature may be related to the onset of antiferromagnetism at ～2.7 K. 1 |
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