The low-temperature thermal expansion and vibrational properties of alkaline earth fluorides

Bailey, A. C.; Yates, B.

doi:10.1088/0370-1328/91/2/317

Cited by 85 publications

(20 citation statements)

References 39 publications

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“…Low-temperature measurements have been reported by Bailey and Yates [1] from 273 K down to about 30 K and by White [2] between 6 and 90 K and between 273 and 293 K. The results of these authors agree and have been reviewed by Barron et al [3]. A linear thermal expansion coefficient of = 1.85 x 10 5K 1at 3 0 0 K h a s been derived on the basis of these measurements.…”

mentioning

confidence: 56%

“…Contrary to this result, the X-ray measurements of Sirdeshmukh and Deshpande [5] in the range 301 to 527 K gave a strongly temperature-dependent expansion coefficient which increases from 2.05 x 10 5 K at 300K to 2.74 x 10-SK -~ at 527K. It has already been pointed out by Bailey and Yates [1] that these resuts do not appear as a smooth continuation of the low-temperature data. On the other hand, although the expansion coefficient given by Kikoin [4] is in excellent agreement with the value at 300 K determined from the low-temperature experiments, it is somewhat surprising that ~ remains constant with increasing temperature.…”

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confidence: 69%

“…On the other hand, although the expansion coefficient given by Kikoin [4] is in excellent agreement with the value at 300 K determined from the low-temperature experiments, it is somewhat surprising that ~ remains constant with increasing temperature. Indeed, if we consider the ~(T) curves measured at T < 300K [1,3] it seems to be more likely that ~ continues to increase with temperature above 300 K, as in found in CaF2 ( [6] and references therein) and SrF2 [7]. Thus, it is obvious that a renewed experimental determination of the thermal expansion coefficients up to a sufficiently high temperature is necessary in order to clarify the thermal expansion behaviour of BaF2 at elevated temperatures.…”

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confidence: 99%

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Thermal expansion of BaF2 from 296 to 1173 K

et al. 1986

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Thermal expansion of BaF2 from 296 to 1173 K

et al. 1986

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“…From our results we obtain for s a value of 1.2 X 10 -3 K -1 , which differs markedly from that reported for nominally pure BaF2, viz. s = 5.37 X 10 -5 K -1 [52]. These interpretations of TS results therefore seem questionable.…”

Section: Broad Absorption Lossesmentioning

confidence: 96%

Low-temperature ionic conductivity and dielectric relaxation phenomena in fluorite-type solid solutions

Wapenaar

Koekkoek

1982

Solid State Ionics

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Low-temperature ionic conductivity and dielectric relaxation phenomena in Ba 1 _xLaxF2+x crystals (1.19 X 10 -3 < x < 0.492) have been studied by ionic thermal current (ITC) and ac dielectric loss (DL) techniques. The conductivity results agree with those of an earlier ~tudy of the same crystals at higher temperatures. At low LaF 3 concentrations, i.e. 1.19 X 10 -3 ~ x ~ 2.37 X 10 -2 , the dielectric spectra show three relaxation peaks, two of which are ascribed to simple associates of interstitial F-ions (Fi) nearest-neighbour (nm) and next-nearest-neighbour (nnn) to substitutional La 3÷ ions (LaBa). They are denoted as type I and II dipoles, respectively. We attribute the third peak to angled ("L-shaped") (LaBa2~'i}' complexes. Relaxation parat~etors for the relaxations are presented. We have calculated effective dipole moments for type I . eli eli .and II dipole8 PI and/Zli , taking rote account the displacements and polarizabilities of the defects. Several combinations of host lattice cations and dQpant ions have been co~idered for the fluorites M l -xRExF2+x, i.e. M = Ca, S~Ba, and RE = La, Eu, Lu. For nearly all combinations the ratio ~[f/~ff is found to have a value of 2.4 ± 0.1. With the tt eII values thus obtained, the dipole concentrations of type I and II dipoles can be calculated. Their dependence on solute content is discussed. In the calculations, Debye-Hiickel-Lidiard interactions between defects and the charge clouds surrounding them have been taken into account. At high concentrations, i.e. 0.133 < x < 0.492, broad structureless absorption losses dominate the dielectric relaxation spectra. These losses are analysed by the fractional polarization (FP) technique, and by a special analysis of the DL data. The feasibility of these techniques is discussed. The analysis reveals that two localized relaxation processes occur in concentrated solid solutions. One is characterized by reorientation activation enthalpies (AH R) which are ghe same as the corresponding conductivity activation enthalpies (AH), and is ascr~ed to F-interstitial motion in crystal areas around defect clusters. The second process is characterized by AH R values which are much lower than AH. We propose that this process is related to F-interstitial reorientation within clusters. The results presented indicate that no typical polarizable cluster is preferred in concentrated Ba I _xLaxF2+x solid solutions.

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“…Bailey and Yates [9] have given the sources of the specific heat and elastic constant data which were used in association with their thermal expansion data in calculating vD(n) as a function of n for -3 5 n 5 6. Their values of vD (n) have been used without modification in calculating OM( T, V ) as described below.…”

Section: The Debye-walk Frequency Integralsmentioning

confidence: 99%

Thermodynamic Calculations of the Debye‐Waller Frequency Integrals of Alkaline Earth Fluorides

Brade

Yates

1969

Physica Status Solidi (b)

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The maximum frequencies of the Debye distributions having the same n-th moments as the vibrational frequency spectra in CaF,, SrF,, and BaF,, calculated from specific heat, thermal expansion, and elastic constant data, have been applied in the quasi-harmonic approximation t o calculate the Debye-Waller frequency integrals of these solids. Highand low-temperature series expansions and Pad6 approximants have been employed to calculate these parameters as functions of temperature between 0 and 300 OK. Good agreement is observed between the values calculated for CaF, and BaF, a t room temperature and those based upon neutron diffraction studies.

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The low-temperature thermal expansion and vibrational properties of alkaline earth fluorides

Cited by 85 publications

References 39 publications

Thermal expansion of BaF2 from 296 to 1173 K

Thermal expansion of BaF2 from 296 to 1173 K

Low-temperature ionic conductivity and dielectric relaxation phenomena in fluorite-type solid solutions

Thermodynamic Calculations of the Debye‐Waller Frequency Integrals of Alkaline Earth Fluorides

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