Bismuth Aluminate BiAlO_(3): A New Lead-free High-T_(C) Piezo-/ferroelectric

摘要

Ferroelectric materials have applications in non-volatile random access memory devices and micro electromechanical systems. For such applications, the materials must remain ferroelectric up to high temperatures. The best materials that currently exist for these applications are lead-containing compounds like Pb(Zr_(1-x)Ti_(x))O_(3). Owing to the toxicity of lead, there is a demand for lead-free high-temperature ferroelectrics. Bismuth aluminate has been predicted to be one such material [1]. In this work, BiAlO_(3) is synthesized using a high-pressure high-temperature technique at 6 GPa and 1000 deg C. The diffraction experiments show that BiAlO_(3) crystallizes in a rhombohedral unit cell that is elongated along the c-axis (R3c; Z velence 6; a velence 5.37546(5) A and c velence 13.3933(1) A). The characterization of the dielectric, ferroelectric, and piezoelectric properties of the ceramic BiAlO_(3) demonstrate that it is indeed a lead-free ferroelectric with a Curie temperature T_(C) > 520 deg C, a piezoelectric coefficient d_(33) velence 28 pC/N and a room-temperature remnant polarization P_(r) velence 9.5 (mu)C/cm~(2). P_(r) increases with temperature, reaching 26.7 (mu)C/cm~(2) at 225 deg C. The dielectric, ferroelectric and piezoelectric properties of BiAlO_(3) are comparable to those of BiFeO_(3) (BFO) and SrBi_(2)Ta_(2)O_(9) (SBT), making it a promising new high-T_(C) lead-free piezo- and ferroelectric for memory and transducer applications.