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Microscopy analysis of the morphology and phase transformation of metastable β-HgI2

XU GANG1,* , CHEN JING1, GU ZHI2, HOU YANNAN1, LI JUNYING1, YANG CONGXIAO1

Affiliation

  1. School of Materials and Chemical Engineering, Xi’an Technological University, Xi’an, 710032, Shaan Xi Province, P. R. China
  2. State Key Laboratory of Solidification Processing, North western Polytechnical University, Xi’an, 710072 , Shaan Xi Province, P. R. China

Abstract

Rhombus-shaped metastable β-HgI2 crystals were grown in a mixture of dimethylsulfoxide and H2O at constant temperature. Crystal growth and phase transformation (β-HgI2→α-HgI2) were investigated in situ using polarizing microscopy. The attachment energy of the main faces of β-HgI2 crystals was calculated to investigate crystal morphology. The results showed that the newly-grown crystal belong to Cmc21 space group, and the included angle of (110) and (1 10 ) planes during crystal growth remains approximately 65.24°, in accordance with that in unit cell of β-HgI2(65.16°). The morphological importance decreases differently as {001} >{110} >{111} >{112} >{010}, indicating a rhombus layer shape under the employed condition. For the β-HgI2→α-HgI2 phase transformation, we fitted the relation between the transformed volume fraction f, and time t, and obtained a growth exponent of n = 1.5, suggesting the growth mode is between one-dimensional and two-dimensional growth. Comparison of the parent and product structures indicates that the metastable β-HgI2→α-HgI2 phase transformation follows a first-order structural reconstruction..

Keywords

Mercuric iodide, Crystal structure, Growth Morphology, Phase transformation.

Citation

XU GANG, CHEN JING, GU ZHI, HOU YANNAN, LI JUNYING, YANG CONGXIAO, Microscopy analysis of the morphology and phase transformation of metastable β-HgI2, Optoelectronics and Advanced Materials - Rapid Communications, 13, 3-4, March-April 2019, pp.267-272 (2019).

Submitted at: June 27, 2018

Accepted at: April 8, 2019