Microwave absorption in single crystals of lanthanum aluminate

Journal Article · Mon Dec 01 04:00:00 EST 1997 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.366433· OSTI ID:552967

Zuccaro, C; Winter, M; Klein, N; Urban, K ^[1]

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1. Forschungszentrum Juelich GmbH, Institut fuer Festkoerperforschung, D-52425 Juelich (Germany)

A very sensitive dielectric resonator technique is employed to measure loss tangent tan{delta} and relative permittivity {epsilon}{sub r} of lanthanum aluminate (LaAlO{sub 3}) single crystals at 4{endash}300 K and 4{endash}12 GHz. A variety of single crystals grown by different techniques and purchased from different suppliers are considered. For T{gt}150K the loss tangent tan{delta} is almost sample independent with linear frequency dependence and monotonous temperature variation from 8{times}10{sup {minus}6} at 300 K to 2.5{times}10{sup {minus}6} at 150 K and 4.1 GHz. In this temperature range the experimental data are explained by a model based on lifetime broadened two-phonon difference processes. The loss tangent below 150 K is characterized by a peak in tan{delta}(T) at about 70 K. The height of this peak is frequency and strongly sample dependent. This leads to a variation of the loss tangent from 10{sup {minus}6} to 1.5{times}10{sup {minus}5} at 77 K and 8.6 GHz, the lowest values are generally achieved with Verneuil grown crystals and approach the intrinsic lower limit predicted by the phonon model. The peak is explained by defect dipole relaxation (local motions of ions). The activation energy of the relaxation process is determined from the measured data to be 31 meV. This low value indicates that the defect dipoles are associated with interstitials, possibly impurities in interstitial positions. Considering absorption due to phonons and due to defect dipole relaxation the loss tangent is calculated for a wide frequency range. {copyright} {ital 1997 American Institute of Physics.}

• OSTI ID: 552967
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 11 Vol. 82; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTRA
AC LOSSES
ALUMINATES
FREQUENCY DEPENDENCE
GHZ RANGE 01-100
INTERSTITIALS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MICROWAVE RADIATION
MONOCRYSTALS
PERMITTIVITY
TEMPERATURE DEPENDENCE