Growing Oriented Layers of Bi4Ti3O12 in Bi2O3/TiO2/SiO2/Nd2O3/Al2O3 Glass-Ceramics by Melt Quenching

Wolfgang Wisniewski,Stanislav Slavov,Yanko Dimitriev,Christian Rüssel

doi:10.1038/s41598-018-26876-6

Wolfgang Wisniewski, Stanislav Slavov + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-26876-6

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Abstract

A glass melt with the composition 24Bi2O3/40TiO2/10SiO2/10Nd2O3/16 Al2O3 was prepared and rapidly quenched between two copper blocks (sample A). A part of this glass was subsequently crystallised at 800 °C for 8 h (sample B). For the preparation of another two samples, the melt was slowly cooled on a cooper plate (sample C) or cast into a graphite mould and subsequently thermally treated at 300 °C for 3 h (sample D). As shown by X-ray diffraction (XRD) and scanning electron microscopy (SEM) including energy dispersive X-ray spectroscopy (EDXS) and electron backscatter diffraction (EBSD) measurements, the rapidly cooled samples contained notable amounts of uncrystallised glassy phase next to the Aurivillius phase Bi4Ti3O12. The latter occurred in higher concentrations in all other samples and formed oriented layers. Minor concentrations of Bi2Al4O9 and Al2O3 were also detected in the microstructure.

Highlights

The excellent ferroelectric properties of crystalline phases in the bismuth titanate family have generated great interest in recent years, mainly due to their high temperature stability and high dielectric constants[1]
In this article we describe the microstructures and phases resulting from four different routes of synthesis which lead to varying degrees of orientation alignment for Bi4Ti3O12
The glass was cooled according to the procedures outlined in Fig. 1: A: quenched to a thickness of 1 mm between two Cu plates, B: part of sample A subsequently heated to 800 °C in an alumina crucible (1 mm wall thickness) with a rate of 7 K/min where it was held for 8 h, C: pouring the melt on a Cu plate so that the final thickness is again 1 mm and letting it cool to room temperature (RT) and D: casting the melt into a graphite mould preheated to 300 °C so that it is filled to a thickness of 8 mm before transferring it to a cooling furnace for 3 h at 300 °C before cooling to RT

Summary

Results and Discussion

A glass of the set composition 30 Bi2O3/50 TiO2/10 SiO2/10 Nd2O3 was melted but the composition determined using energy dispersive X-ray spectroscopy (EDXS) after melting was ≈24 Bi2O3 40 TiO2 10 SiO2 10 Nd2O3 16 Al2O3 in mol%. As this microstructure occupies most of the volume in this sample and the corresponding XRD-pattern B in Fig. 2 only shows orthorhombic Bi4Ti3O12, it is plausible to conclude that these structures are composed of this phase. Textures were not detected in EBSD-scans performed in the bulk, supporting the assumption that the crystals here formed without a reference system comparable to the top and bottom interfaces

Large crystal top

Ti Si Al

Methods

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