Synthesis and Physical Properties of Single Crystals and Ceramics of New Ferroelectric BaTi2O5

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Single crystals of ferroelectric BaTi2O5 were grown by a floating zone method, and the dielectric constant and specific heat were measured in a temperature range of 300–800 K. The dielectric constant and dielectric loss along the $b$-axis show a large dielectric dispersion at $T_{\text{C}}=730$ K, similar to the ferroelectric phase transition of the order-disorder type. Transition enthalpy and transition entropy were estimated to be $\Delta H=98.6$ J/mol and $\Delta S=0.136$ J/molK, respectively. The optical absorption edge of the crystals exists near 365 nm. Single-phase BaTi2O5 powder was successfully synthesized through a sol-gel route, using barium diethoxide and titanium tetraisopropoxide, and the porous ceramics sintered at 1375 K show a broad maximum in the electrical capacitance vs $T$ curve at approximately 600 K.
2005-09-15