Abstract
The linear thermal expansions of åkermanite (Ca2MgSi2O7) and hardystonite (Ca2ZnSi2O7) have been measured across the normal-incommensurate phase transition for both materials. Least-squares fitting of the high temperature (normal phase) data yields expressions linear in T for the coefficients of instantaneous linear thermal expansion,
for åkermanite:
for hardystonite:
Although there is considerable strain for temperatures within 10° C of the phase transition, suggestive of a high-order phase transition, there appears to be a finite ΔV of transition, and the phase transition is classed as “weakly first order”.
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Webb, S.L., Ross, C.R. & Liebertz, J. Thermal expansion and spontaneous strain associated with the normal-incommensurate phase transition in melilites. Phys Chem Minerals 18, 522–525 (1992). https://doi.org/10.1007/BF00205268
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DOI: https://doi.org/10.1007/BF00205268