Raman spectroscopic investigations of dicalcium silicate polymorphs and high-temperature phase transformations
- and others
Polymorphs and high-temperature phase transformations of dicalcium silicate (Ca{sub 2}SiO{sub 4}) are investigated on powdered samples, using Raman scattering techniques. Raman spectra at room conditions of pure {gamma}- and {beta}-Ca{sub 2}SiO{sub 4} and stabilized {beta}-,{alpha}{prime}{sub L}-, and {alpha}-Ca{sub 2}SiO{sub 4} are presented in the frequency range of 110--1,110 cm{sup {minus}1}. Each polymorph can be identified by its Raman spectrum, even though strong similarities exist between the {beta}, {alpha}{prime}{sub L}, and {alpha} phases. In-situ high-temperature Raman spectroscopic studies in the temperature range of 298--1,433 K on heating and cooling also are reported, starting from {gamma}-Ca{sub 2}SiO{sub 4}. Modifications occurring in the Raman spectra recorded in the wavenumber range of 90--1,000 cm{sup {minus}1} show up during heating, the irreversible {gamma} {r_arrow} {alpha}{prime}{sub L} phase transformation. Coexistence of {gamma} and {alpha}{prime}{sub L} grains is observed in the temperature range of 1,091--1,119 K at least. The differences observed between the {gamma}-Ca{sub 2}SiO{sub 4} and {alpha}{prime}{sub L}-Ca{sub 2}SiO{sub 4} Raman spectra suggest that this phase transformation is a reconstructive first-order transition. The reversible {alpha}{prime}{sub L} {r_equilibrium} {beta} phase transformation also is described. Raman spectra of pure {beta} and {alpha}{prime}{sub L} phases resemble each other. The transition occurs from 949 K, on cooling, to 960--988 K, on heating, with a hysteresis probably dependent on the thermal history of the starting product. From the Raman scattering observations, this phase transformation also is considered as a first-order transformation and is probably of a displacive type.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 483665
- Journal Information:
- Journal of the American Ceramic Society, Vol. 80, Issue 2; Other Information: PBD: Feb 1997
- Country of Publication:
- United States
- Language:
- English
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