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AIOFM Develops A New Method to Uncover the Secrets in LBO Crystal Growth TEXT SIZE: A A A
Date:2017.10.25 Author:ZHANG Shujie; YAO Bo Clicks:

Scientists at Anhui Institute of Optics and Fine Mechanics (AIOFM), Hefei Institutes of Physical Science, Chinese Academy of Sciences managed to develop a new method to uncover the secrets in LiB3O5 (LBO) crystal growth, according to a paper newly published in the journal of CrystEngComm as cover article.

LBO crystal, which was first invented in China, is a world-renowned nonlinear optical material and is excepted to be applied in laser nuclear fusion, high energy physics and other important fields.

From the beginning of this century, many advanced countries in the field of crystal research, such as China, Russia, and the United States, continue to increase the investment in large-size and high-quality LBO crystals in order to realize frequency conversion of high-power lasers.

However, many basic scientific problems of LBO crystal growth remain unresolved.

After years of effort, Prof. WAN Songming’ group at AIOFM, cooperating with Prof. YOU Jinglin’ group at Shanghai University, established a new method, which combines high temperature Raman experimental technique with density functional theory, for analyzing complicated melt structures.

On the basis of this method, the joint team studied the phase transition, melt structure and growth mechanism of the LBO crystal to uncover the scientific essence behind several LBO crystal growth phenomena.

 

 Fig.1 Structural transformations in the LBO solid-liquid phase transition. (Image by WAN Songming)

In these studies, they firstly studied the structure transition of the LBO crystal during the melting process.

Except for the thermodynamic equilibrium product Li3B7O12, they also found a dynamics intermediate product Li2B4O7during this process for the first time.

Upon melting, the three-dimensional B3O3?4 (?-bridged oxygen atom) frame of the LBO crystal first decomposes into B4O5?4 and B2O3, and eventually converts into one-dimensional B3O4?2 chains (see Fig. 1). The structural memory phenomena of the LBO melt are explained successfully. (CrystEngComm 2015, 17, 9357-9362; J. Cryst. Growth 2016, 435, 1-5).

 

 Fig.2 The paper published in CrystEngComm and featured as a cover. (Image by WAN Songming)

Then, the team studied the melt composition-structure relationship in the Li2O-B2O3 pseudo-binary system, and established a complete structural spectrum of lithium borate melts.

The results were used to explain the high viscosity and the viscosity anomaly of the Li2O·4B2O3 melt (with the B2O3 flux to grow the LBO crystal), and to completely understand the micro-process of the LBO crystal growth. (Inorg. Chem. 2016, 55, 7098-7102; CrystEngComm 2017, 19, 5721-5726, cover article, see Fig. 2).

 

 Fig.3 A substitution reaction between a Mo3O102-group and a B3O42-chain. (Image by ZHANG Shujie)

The Raman spectra of Li2Mo2O7 and Li2Mo3O10 melts were also studied in detail.

According to the spectral changes of the Li2Mo3O10 melt (another flux to grow the LBO crystal) during a LBO crystal melting process, the team found a substitution reaction of Mo3O102- groups with the LBO crystal, which produces MoO3·B3O42- intermediate of complex and Mo2O72- groups (see Fig. 3).

The MoO3·B3O42- intermediate of complex is the key to understanding the micro-process of the LBO crystal growth (Inorg. Chem. 2017, 56, 3623-3630).

The above works provide a new method for analyzing complicated melt structures, and reveal the melt structure and growth mechanism of the LBO crystal. Meanwhile, these works also are expected to promote the development of science and technology of crystal growth by the flux method.

These works were supported by the National Natural Science Foundation of China (No. 51372246).

Link to the papers:

1. Structural studies of a Li2O·4B2O3 melt by high-temperature Raman spectroscopy and density functional theory

2. In situ Raman investigation of a LiB3O5 melt toward understanding the structural memory phenomena

3. Reinvestigation on the phase transition of a LiB3O5 crystal near its melting point

4. Raman spectral and density functional theory analyses of the CsB3O5melt structure

5. Investigation on the structure of a LiB3O5–Li2Mo3O10high-temperature solution for understanding the Li2Mo3O10flux behavior

 

 

 
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