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Perturbation of fundamental band edge absorption of NaClO3 crystals at high temperatures
Vol. 8, No. 8 7.
ABSTRACTS OF PAPERS TO APPEAR IN
MAGNETIC SUSCEPTIBILITY OF EUROPIUM TRIFLUORIDE S. Kern, Department of Physics, Colorado State University, Fort Collins, Colorado U.S.A., P.M. Raccah, Lincoln Laboratory, M.I.T., Lexington, Massachusetts U.S.A. and A. Tveten, Department of Physics, Colorado State University, Fort Collins, Colorado U.S.A.
Our previous measurement of the magnetic susceptibility of europium trifluoride from liquid helium to room temperature has been extended to 750°K.With the aid of the recent spectroscopically determined values of the lowflying energy levels of EuF3 a simple crystal field analysis has been used to calculate the expected temperature variation of the susceptibility. When an accurate account is taken of the sample impurities, the calculated and experimental values agree to within approximately one per cent over the entire region of measurement. Received 26 January 1970
J. PHYS. CHEM. SOLIDS
111
above 120°C could be analysed in a similar manner and the activation energy of 1.45 ± 0.05 eV so obtained is in reasonable agreement with that obtained from optical absorption studies. The additional absorption may be attributed to the perturbation of the fundamental absorption band due to defects formed at higher temperatures. Received 30 December 1969
9.
DETERMINATION OF VALENCE AND COORDINATION OF IRON IN OXIDIC COMPOUNDS BY MEANS OF THE X-RAY FLUORESCENCE EMISSION SPECTRUM A.S. Koster and G.D. Rieck, Technical University, Eindhoven, the Netherlands
The dependence of the X-ray fluorescence in the K13 spectrum of oxidic iron compounds on chemical and crystallographic structure was studied. The position of the line K~~ is mainly determined by the valence of the iron, the position of K13 is also influenced by the coordination of the iron ions. The satellites occurring in the K13 spectrum give, in a qualitative way, additional information about structure. ~
8.
PERTURBATION OF FUNDAMENTAL BAND EDGE ABSORPTION OF NaC1O3 CRYSTALS AT HIGH TEMPERATURES S.B.S. Sastry, R.B. Tripathi and C. Ramasastry, Solid State Physics Laboratory, Physics Department, Indian Institute of Technology, Madras 36, India
The fundamental absorption band edge of NaC1O3 crystal showed a shift towards longer wavelengths with increase in temperature. There is also evidence of formation of a new-band at temperature higher than about 120°C. The shift is nearly linear up to about 120°C, but it is much larger than the linear rate as the melting point (~250°C) is approached. The excess absorption is assumed to be due to the thermally produced lattice disorder and analysis yielded 1.40 ±0.05eV for the energy of formation of the defect. The anomalous thermal expansion of the crystal reported by earlier workers at temperatures
Received 24 July 1969 Revised 10 November 1969
10.
PHONON FREQUENCIES OF RARE EARTH TRICHLORIDES WITH UNIT CELLS OF DIFFERENT DIMENSIONS G. Schaack and J.A. Koningstein, Department of Chemistry, Carleton University, Ottawa 1, Ontario, Canada
The phonon Raman spectra of isomorphous single crystals of LaC1 CeC1 NdC13, EuCl3 and GdC13 have been investigated. GdC13, the last in the series of hexagonal rare-earth trichiorides, has a phonon spectrum, which differs markedly from the other spectra. The shift of the phonon frequencies with the decreasing volume of the unit cell for increasing atomic ~,
~,
ABSTRACTS OF PAPERS TO APPEAR IN
MAGNETIC SUSCEPTIBILITY OF EUROPIUM TRIFLUORIDE S. Kern, Department of Physics, Colorado State University, Fort Collins, Colorado U.S.A., P.M. Raccah, Lincoln Laboratory, M.I.T., Lexington, Massachusetts U.S.A. and A. Tveten, Department of Physics, Colorado State University, Fort Collins, Colorado U.S.A.
Our previous measurement of the magnetic susceptibility of europium trifluoride from liquid helium to room temperature has been extended to 750°K.With the aid of the recent spectroscopically determined values of the lowflying energy levels of EuF3 a simple crystal field analysis has been used to calculate the expected temperature variation of the susceptibility. When an accurate account is taken of the sample impurities, the calculated and experimental values agree to within approximately one per cent over the entire region of measurement. Received 26 January 1970
J. PHYS. CHEM. SOLIDS
111
above 120°C could be analysed in a similar manner and the activation energy of 1.45 ± 0.05 eV so obtained is in reasonable agreement with that obtained from optical absorption studies. The additional absorption may be attributed to the perturbation of the fundamental absorption band due to defects formed at higher temperatures. Received 30 December 1969
9.
DETERMINATION OF VALENCE AND COORDINATION OF IRON IN OXIDIC COMPOUNDS BY MEANS OF THE X-RAY FLUORESCENCE EMISSION SPECTRUM A.S. Koster and G.D. Rieck, Technical University, Eindhoven, the Netherlands
The dependence of the X-ray fluorescence in the K13 spectrum of oxidic iron compounds on chemical and crystallographic structure was studied. The position of the line K~~ is mainly determined by the valence of the iron, the position of K13 is also influenced by the coordination of the iron ions. The satellites occurring in the K13 spectrum give, in a qualitative way, additional information about structure. ~
8.
PERTURBATION OF FUNDAMENTAL BAND EDGE ABSORPTION OF NaC1O3 CRYSTALS AT HIGH TEMPERATURES S.B.S. Sastry, R.B. Tripathi and C. Ramasastry, Solid State Physics Laboratory, Physics Department, Indian Institute of Technology, Madras 36, India
The fundamental absorption band edge of NaC1O3 crystal showed a shift towards longer wavelengths with increase in temperature. There is also evidence of formation of a new-band at temperature higher than about 120°C. The shift is nearly linear up to about 120°C, but it is much larger than the linear rate as the melting point (~250°C) is approached. The excess absorption is assumed to be due to the thermally produced lattice disorder and analysis yielded 1.40 ±0.05eV for the energy of formation of the defect. The anomalous thermal expansion of the crystal reported by earlier workers at temperatures
Received 24 July 1969 Revised 10 November 1969
10.
PHONON FREQUENCIES OF RARE EARTH TRICHLORIDES WITH UNIT CELLS OF DIFFERENT DIMENSIONS G. Schaack and J.A. Koningstein, Department of Chemistry, Carleton University, Ottawa 1, Ontario, Canada
The phonon Raman spectra of isomorphous single crystals of LaC1 CeC1 NdC13, EuCl3 and GdC13 have been investigated. GdC13, the last in the series of hexagonal rare-earth trichiorides, has a phonon spectrum, which differs markedly from the other spectra. The shift of the phonon frequencies with the decreasing volume of the unit cell for increasing atomic ~,
~,