MATÉRIAUXCRYSTAL CHEMISTRY OF PEROVSKITE-LIKE LAYER-TYPE FERROELECTRICSReport as inadecuate




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Abstract : The number of monooctahedral layers in the perovskite-like package m depends on the value of tolerance factor t. The lower and upper criteria of layer structure formation are t1 ≈ 0.87 and tu ≈ 0.99. In Bi2O22+ layers only one of the Bi3+ ions may be replaced, and only by trivalent cation ; that leads to increasing of Tc. Depending upon the polarizability of A and O2-ions increasing of m causes both raising and lowering of Tc. Bi2WO6 is the first one-layer ferroelectric with Tc ≈ 950 °C. Crystals Bi2NbO5F and Bi2TaO5F are also one-layer ferroelectrics with Tc ≈ 30 °C and 10 °C.





Author: I. Ismailzade

Source: https://hal.archives-ouvertes.fr/



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