The formation of intergrowth compounds

Most compounds have been found in the Ba0-Nb0-Nb02 system and the corresponding compositional diagram is shown in Fig. 16. Not all the K, Sr, and Eu analogs have been prepared (Table 3). The difficulties in preparation are probably because of the smaller size difference between NbO and BaNbOs compared with ANbOs A = K, Sr, and Eu, see Table 4. 

The syntheses of these compounds often have been far from straightforward in the Ba-Nb-0 system. At moderate temperatures (1050-1250 K) disordered crystallites with a Ba/Nb ratio of approximately 1 4 exist as a single phase in the shaded region on the right hand side of the BaNb03-NbO line, in Fig. 17. 

To obtain the ordered compounds higher temperatures and prolonged annealing are needed. V.G. Zubkov et have studied in detail the formation of these 

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