Thermal expansion anisotropy and individual bond expansion coefficients in ternary chalcopyrite compounds

Neumann, H.

doi:10.1002/crat.2170220519

Cited by 18 publications

(10 citation statements)

References 29 publications

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“…The temperature dependent behaviour of the degrees of freedom of the chalcopyrite type structure, the tetragonal disortion and the tetragonal deformation were also revealed. The first shows a rather weak temperature dependence α u~0 in the range from room temperature up to the critical region (T trans -10K) as expected from theory [8]. Within the critical region the anion displacement parameter u increases strongly.…”

Section: Discussionmentioning

confidence: 71%

“…Beyond this, the temperature dependence of the anion parameter u is rather weak up to within 10 K of T trans . This behaviour, namely α u =0, has been previously reported in terms of the individual bond expansion coefficients α AC and α BC of A I B III C 2 VI chalcopyrite compounds, calculated from the principal linear thermal expansion coefficients of the lattice parameters using two different models, the B-C regular tetrahedron model and a model with a temperature independent free parameter (namely the anion parameter u) of the lattice [8]. It was shown, that the bond expansion coefficients derived from the latter model are in better agreement with those trends found for the interatomic forces in chalcopyrite compounds.…”

Section: Resultsmentioning

confidence: 78%

“…Then the anion parameter increases strongly with increasing temperature to u=0.2436(25) at T trans . Thus the experimental evidence for the assumtion α u = 0 is given at least in the temperature region discussed in [8].…”

Section: Resultsmentioning

confidence: 97%

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In-situ investigation of the temperature dependent structural phase transition in CuInSe2 by synchrotron radiation

Schorr¹,

Géandier²

2006

Cryst. Res. Technol.

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The temperature dependent structural phase transition from the tetragonal chalcopyrite like structure to the cubic sphalerite like structure in CuInSe 2 was investigated by in-situ high temperature synchrotron radiation X-ray diffraction. The data were collected in 1K steps during heating and cooling cycles (rate 38 K/h). The Rietveld analysis of the diffractograms led us to determine the temperature dependence of the lattice parameters, including the tetragonal deformation, I1-ηI, and distortion Iu-¼I (η=c/2a, a and c are the tetragonal lattice constant; u is the anion x-coordinate). The thermal expansion coefficients α a and α c of the tetragonal lattice constant which are related to the linear thermal expansion coefficient α L were obtained, as were α a of the cubic lattice constant, also α u and α η . The transition temperature is clearly identified via a strong anomaly in α L . The temperature dependence of the anion position parameter was found to be rather weak, nearly α u~0 , whereas α η increases slightly. However, both increase strongly when approaching to within 10 K of the transition temperature (the critical region) and I1-ηI as well as Iu-¼I go to zero with IT-T trans I 0.2 approaching the phase transition. The cation occupancy values, derived from the Rietveld analysis, remain constant below the critical region. Close to the transition temperature, the number of electrons at the Cu site increases with a dercrease in the number of electrons at the In site with increasing temperature, indicating a Cu-In anti site occupancy, which is assumed to be the driving force of the phase transition. At the transition temperature 67% of Cu + were found to occupy the Me1 site with a corresponding 67% of In 3+ at the Me2 site. Although full disorder is reached with 50%, this level seems to be high enough that the phase transition takes place. The order parameter of the phase transition, goes with IT-T trans I β to zero with the critical exponent β=0.35(7) which is in good agreement to the critical exponent β=0.332 calculated for order-disorder transitions according to the Ising model.

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Section: Discussionmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 78%

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In-situ investigation of the temperature dependent structural phase transition in CuInSe2 by synchrotron radiation

Schorr¹,

Géandier²

2006

Cryst. Res. Technol.

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“…It is worth to notice that the anion position parameter u remains nearly constant up to the critical region. This behaviour, namely du/dT = α u = 0, has been predicted theoretically [14], but never proved experimentally due to the an absence of experimental data. The first experimental evidence is now given in this study.…”

mentioning

confidence: 85%

Some are different from others: high temperature structural phase transitions in ternary chalcopyrites

Schorr

Géandier

Корзун

2006

Phys. Status Solidi (c)

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The high temperature behaviour of A I B III X 2 VI chalcopyrites (A=Cu; B=Al, Ga und In; X=S, Se, Te) was studied by in-situ high temperature synchrotron radiation X-ray diffraction. Structural phase transitions from the α phase with chalcopyrite structure to the β phase with sphalerite structure were obtained in the compounds CuInX 2 and CuGaTe 2 . The driving force of this order-disorder transition is a Cu-In anti site occupancy starting in the critcal temperature region, nearly 10 K before the transition temperature. The order parameter of the phase transition, expressed ase e e n n n = − , goes within the critical region to zero according to IT -T trans I β with the critical exponent β = 0.35(7). Structural transitions were also obtained in CuAlTe 2 and CuGaSe 2 , but they show a different character. In the first compound it goes with the occurrence of a small two phases region, in the second with the formation of an other, unknown phase. Furthermore neither critical behaviour nor an anti site occupancy of the cations is observed.

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“…(i) In the Cu-type compounds, the linear thermal expansion coefficients α a and α c are always positive at room temperature with α a < α c while in the Ag-type compound, α c is negative [2,3]. (ii) In the Cu compounds, the isothermal compressibility is χ a > χ c , while in AgGaSe 2 the c parameter is more compressible than the a parameter [4,5].…”

mentioning

confidence: 96%

Anomalous pressure dependence of acoustic phonons of AgGaSe₂ investigated by inelastic neutron scattering to 4.3 GPa

Klotz¹,

Derollez²,

Fouret

et al. 2003

Physica Status Solidi (b)

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The pressure dependence of the transverse acoustic (TA) phonons along [100] and [001] and the lowfrequency optical Λ 3 modes of AgGaSe 2 has been measured at pressures to 4.3 GPa by inelastic neutron scattering. We find an exceptionally strong frequency decrease of the TA modes with Grüneisen parameters as low as -10 for wave vectors close to the zone centre. The associated elastic coefficient C 44 decreases by ~50% between 0 and 2.6 GPa. The softening also affects the optical modes to a less extent. These lattice dynamical anomalies seem to be related to a continuous structural phase transition located at ~2.6 GPa. Single crystal X-ray diffraction results are consistent with a monoclinic lattice of the high pressure phase which can be regarded as a slightly distorted chalcopyrite structure, similar to AgGaS 2 .

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Thermal expansion anisotropy and individual bond expansion coefficients in ternary chalcopyrite compounds

Cited by 18 publications

References 29 publications

In-situ investigation of the temperature dependent structural phase transition in CuInSe2 by synchrotron radiation

In-situ investigation of the temperature dependent structural phase transition in CuInSe2 by synchrotron radiation

Some are different from others: high temperature structural phase transitions in ternary chalcopyrites

Anomalous pressure dependence of acoustic phonons of AgGaSe₂ investigated by inelastic neutron scattering to 4.3 GPa

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Thermal expansion anisotropy and individual bond expansion coefficients in ternary chalcopyrite compounds

Cited by 18 publications

References 29 publications

In-situ investigation of the temperature dependent structural phase transition in CuInSe2 by synchrotron radiation

In-situ investigation of the temperature dependent structural phase transition in CuInSe2 by synchrotron radiation

Some are different from others: high temperature structural phase transitions in ternary chalcopyrites

Anomalous pressure dependence of acoustic phonons of AgGaSe2 investigated by inelastic neutron scattering to 4.3 GPa

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Anomalous pressure dependence of acoustic phonons of AgGaSe₂ investigated by inelastic neutron scattering to 4.3 GPa