Tantalate alkoxides

For more than 30 years at Lomonosov Moscow State University, later at Karpov Institute of Physical Chemistry, and recently at the Swedish University of Agricultural Sciences, Uppsala (V. G. Kessler), the authors of this book have systematically studyiedthe synthesis and properties of homometallic alkoxides of Groups I-Vm of the Periodic Table, the bimetallic derivatives (alkox-oaluminates, -titanates, -zirconates, -niobates, -tantalates, -molybdates, -tung-... 

Some examples of application of metal alkoxides for synthesis of ferroe-lectrics such as BaTi03-based materials, complex niobates and tantalates, PZT andPLZT-materials, and high-temperature superconductors are discussed below. 10.1. Barium titanate and BaTiOj-based solid solutions... 

All alkoxide routes appear to be limited to obtaining PNM [88a] and lithium or potassium niobate or tantalate [102a]. For the latter, the formulation of the mixed-metal alkoxide MM (OR)6, M = Nb, Ta, is in agreement with that of the material. Epitaxial thin films of LiNbOa on sapphire could be obtained [103]. The use of a mixed-metal MgNb2(OR)i2 species (R = Et [105], C2H40Me [104]) has been shown to promote the formation of the perovskite phase for PNM. 

As emphasized in the opening paragraph of this section, heteroalkoxoniobates and -tantalates are less stable than those of aluminates and zirconates this aspect is also reflected in the chemistry of their homo-alkoxides. The chemistry of hetero-metal alkoxides of those two metals is dominated in most cases (particularly with primary alcohols) by their tendencies for disproportionation as well as formation of oxo-derivatives. Two review articles on these heterometal alkoxides reflect these aspects prominently, even questioning the validity of some earlier findings. 

Figure 27.10 Ferroelectric strontium bismuth the larger grain size of the surface microstruc-tantalate (Sro BBi2.2Ta209) thin films prepared tures of the films prepared from the tantalum from the sols of Figure 27.9 (a) tantalum pen- pentaglycolate sols and the larger values of taethoxide sols and (b) tantalum pentaglyco- the remanent polarization (5Pr) obtained in late sols. SEM images of the top surfaces of these films compared with the films prepared the films are shown, as well as the ferroelectric from the tantalum alkoxide-based sol [47]. hysteresis loops measured in these films. Note...

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