CM03.03.07 : First Synthesis of Dravite by High Pressure Solid-State Reaction

5:00 PM–7:00 PM Apr 3, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E

Zhao Changchun1 Kairen Chen1 Xinghui Gai1 You Shan1 Munan Hao1

1, China University of Geosciences, Beijing, , China

Tourmaline is an important function material due to its excellent physical properties such as spontaneous polarization, pyroelectricity, infrared radiations, and can serve as a petrogenetic monitor of the origin and evolution [1]. Because of the diverse composition and crystal defect from different origins, natural tourmaline is difficult to explore its potential in applications. Till now, many scientists have synthesized tourmaline containing many elements (K, Li, and NH4) through hydrothermal method with high pressure and temperature [2-4]. However, extreme reaction condition and minor sizes of the synthetic crystal (only several microns) are required in such methods. To solve these issues, a new high pressure solid-state method was present and dravite has been firstly synthesized in the present work. It provides an creative synthetic method for the synthesis of tourmaline and shed light upon the large-scale applications of tourmaline.
In this paper, polycrystalline dravite was prepared by using a solid-state reaction method under high pressure and temperature. Synthesis involved a solid-state method at 770-900K and a pressure of 5-7 GPa in mixture of powered Na2O2, Mg(OH)2, MgO, Al2O3, SiO2 and B2O3 with high purity. The growing crystal size is up to Æ0.1mm. Based on XRD and EMPA, it can conclude that dravite was successfully synthesized with a small quantity of SiO2 and Al2O3. The mole ratio of chemical composition are emerged as n(Na): n(Mg) : n(Al): n(Si): n(B) : n(H)=1.032: 2.987: 6.017: 5.982: 3: 4, consistent with the mole ratio of the general formula. Pyroelectricity of the synthetic dravite and natural dravite were measured by TF3000 ferroelectric analyzer. According to the comparison of their pyroelectric coefficient, the pyroelectricity of synthetic dravite are found to be enormously enhanced than natural dravite. These findings provide important insight into the synthesis of bulky tourmaline with different chemical compositions and serve as the role of extending the wide application of tourmaline.

[1] Encarnación roda-robles, William simmons, et al. AM MINERAL 100, 95-109(2015).
[2] Eleanor J. Berryman, Bernd Wunder, et al. Contrib Mineral Petrol 169, 539-542(2015).
[3] Martin Kutzschbach, Bernd Wunder, et al. Phys Chem Minerals 44, 353-363(2017).
[4] Bernd Wunder, Eleanor Berryman, et al. AM MINERAL 100, 250-256(2015).