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Bismuth borates: two new polymorphs of BiB3O6
Linyan Li1, Guobao Li, Yingxia Wang
1State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, PR China.
Inorganic Chemistry
|November 8, 2005
Summary
Two new bismuth borate (BiB3O6) polymorphs, beta-BiB3O6 (I) and gamma-BiB3O6 (II), were discovered at low temperatures. These centrosymmetric structures differ from the nonlinear optical alpha-BiB3O6, suggesting they are low-temperature or high-pressure forms.
Area of Science:
- Materials Science
- Crystallography
- Solid State Chemistry
Background:
- Bismuth borate (BiB3O6) exhibits unique nonlinear optical (NLO) properties attributed to its noncentrosymmetric alpha-polymorph.
- Understanding polymorphism is crucial for tailoring material properties.
Purpose of the Study:
- To identify and characterize new polymorphs of BiB3O6.
- To investigate the structural relationships between different BiB3O6 polymorphs.
- To determine the conditions under which these new polymorphs form.
Main Methods:
- Low-temperature synthesis using boric acid flux.
- X-ray diffraction for crystal structure determination.
- Calculation of lattice parameters and density.
Main Results:
- Discovery of two new BiB3O6 polymorphs: beta-BiB3O6 (I) and gamma-BiB3O6 (II).
- Both new polymorphs crystallize in the centrosymmetric space group P2(1)/n.
- Detailed lattice parameters for both beta-BiB3O6 (I) and gamma-BiB3O6 (II) were determined.
- Structural analysis revealed close relationships between the alpha, beta, and gamma polymorphs, with beta and gamma structures described as additive products of alpha and beta, respectively.
- Calculated densities support the proposal of I and II as low-temperature (high-pressure) polymorphs.
Conclusions:
- Beta-BiB3O6 (I) and gamma-BiB3O6 (II) represent new low-temperature/high-pressure polymorphs of BiB3O6.
- The structural evolution among BiB3O6 polymorphs involves layered and framework structures.
- These findings contribute to the understanding of bismuth borate polymorphism and phase transitions.