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Using a new composite flux and an improved growth process, large and high-quality ferroelectric SrBi2Ta2O9 (SBT) single crystals (up to 25 × 20 mm2 area) were successfully grown from high-temperature solutions. The effects of chemical, thermodynamic, and kinetic parameters on the growth results were systematically studied. The optimum system for the growth of SBT crystals has been identified. B2O3 additive was shown to play an important role in improving the effectiveness of the Bi2O3 solvent. The grown SBT single crystals exhibit a dominant (001)-orientation and large single-domain areas. The dielectric and ferroelectric properties measured in relation to crystal orientations have confirmed the absence of any polarization component normal to the (Bi2O2)2+ sheets of the structure, indicating a high anisotropy in the properties.

I. INTRODUCTION

In the mid 1980’s, ferroelectric Pb(ZrxTi1−x)O3 (PZT) in the form of thin films fabricated at reasonable temperature was demonstrated to be the primary candidate for nonvolatile random access memory (NVRAM), and it has long been investigated for that purpose since then. However, a few problems arise in the use of PZT, such as aging, retention, imprint, and most importantly fatigue, which is a decrease in switchable polarization as the number of polarization reversals increases.1–3 In the last 10 years, ferroelectric SrBi2Ta2O9 (SBT), which is a member of the Aurivillus family with a layered perovskite structure, has emerged as a new promising candidate.4 The particular interest of SBT for the purposes of NVRAM is mainly due to its ability to demonstrate a relatively high fatigue resistance and a good data retention which lasts up to 10 years.5,6 As a result, numerous studies have been undertaken on the synthesis and characterization of SBT ceramics and thin films. However, the degree of success has been limited because of the variation of quality, orientations, grain boundary, and grain size resulting from the different techniques used for the synthesis of polycrystalline thin films.2,4,7–9 The ferroelectric and related properties of SBT appear as a very complex behavior resulting from the structural and crystal chemistry features. It is known that the polarization switching and hence the ferroelectricity depend very sensitively upon the crystallographic orientations (highly

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II. EXPERIMENTAL A. Preparation of SBT powder

Polycrystalline SBT powder was first synthesized via solid-state reactions using strontium acetate, Sr(OOCCH3)2 ⭈ 1/2H2O (Reagent grade, Alfa Aesar),

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anisotropic) and the nonstoichiometry of composition.10,11 The properties of SBT polycrystalline or oriented thin films also depend closely upon many processing and microstructural variables (such as the temperature of deposition, grain size and orientations, substrates), which results in the difficulties in fully investigating and exploring the properties of SBT. To characterize the intrinsic properties a