Effects of Ionic Size in the Tetrahedral and Octahedral Sites on the Thermal Expansion of Low‐Temperature Cordierite

Miyake, Akira

doi:10.1111/j.1551-2916.2005.00059.x

Cited by 11 publications

(2 citation statements)

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“…This result can be understood from the dopant size. Previous MD simulation by Miyake suggests that increasing the ionic size of T2 site results in decreasing the c‐axis lattice constant. Similar conclusion has been also obtained from our AIMD simulation: First, the ionic radius of Ti is slightly larger than Ge, and therefore much larger decrease in c‐lattice constant is observed in the Ti dopant systems.…”

Section: Resultsmentioning

confidence: 96%

“…The recent phonon analysis by Li et al 24 shows quite reasonable agreement with experimental CTE within the moderate temperature region, whereas the vibration approach sometimes has difficulty in reproducing the high-temperature region because vibration analysis tends to underestimate the entropy effect. An alternative approach is classical molecular dynamics (MD), and three types of MD simulations have been reported [25][26][27] to investigate the ionic size effect on thermal expansion mechanism. Although these MD simulations can qualitatively reproduce the experimental thermal expansion, the NTE mechanism has not yet been elucidated.…”

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confidence: 99%

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Thermal expansion mechanism of cordierite with titanium or germanium doping based on ab initio molecular dynamics simulation

Bai

Nakata

2019

J Am Ceram Soc

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A unique feature of cordierite is the negative thermal expansion of its c‐axis, while the a‐ and b‐axes show positive thermal expansion behavior. The thermal expansion mechanism of cordierite has been investigated in many theoretical studies, but the effect of Ti or Ge doping has not yet been studied theoretically. Here, we investigate the thermal expansion behavior of Ti‐ and Ge‐doped cordierite by ab initio molecular dynamics (AIMD) simulation. The computational cost of AIMD simulation for cordierite doped with Ti or Ge is challenging due to the many different configurations of crystal models. We overcame this computational difficulty by separating the respective models into groups with identical symmetry, then we performed MD simulation for each different symmetry crystal model. To understand the mechanism of the negative thermal expansion of the c‐axis, we investigated the changes in all the bond lengths and angles. We found that the negative thermal expansion of the c‐axis is coupled with the increase in the O–Al–O angle and the shrinkage of the O–Si–O angle at the T1 site in cordierite, which suggests the rotation of the six‐membered ring. This study provides insight into the mechanism of thermal expansion of cordierite with Ti and Ge doping. Moreover, the approach presented here can be generally applied to investigate the thermal expansion behavior of other ceramic materials within reasonable accuracy and computational cost.

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Section: Resultsmentioning

confidence: 96%

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confidence: 99%