Preparation of BaTi<SUB>2</SUB>O<SUB>5</SUB> Single Crystal by a Floating Zone Method

Abstract

Single crystalline BaTi 2 O 5 was prepared by a floating zone method. The single crystal was transparent having a (001) cleavage plane. The space group was C2, and the lattice parameters were a ¼ 1:6909ð9Þ nm, b ¼ 0:3937ð1Þ nm, c ¼ 0:9419ð4Þ nm and ¼ 103:12ð6Þ. The permittivity perpendicular to a (010) plane showed the maximum value of 20500 at 748 K. The permittivity perpendicular to (100) and (001) planes were about 140 and 70, respectively, independent of temperature.

Effect of Oxygen Partial Pressure on Structure and Dielectric Property of BaTi<SUB>2</SUB>O<SUB>5</SUB> Films Prepared by Laser Ablation

“…For BaTi 2 O 5 crystals, the (020) plane should be one of the most stable planes. 8,9) The (710) plane is slanted from the (020) plane and would have higher energy than the (020) plane. At a too low P O2 (P O2 < 10 Pa), the ablated species would have excess kinetic energy on the substrate surface, forming a less stable plane, i.e., (710) plane.…”

“…Therefore, many researches have been conducted to develop a new lead-free material having a high T c . Recently, a TiO 2 -rich compound in the BaO-TiO 2 system, BaTi 2 O 5 , was found to be ferroelectric by our group 8,9) and Akishige et al 10) Single crystalline BaTi 2 O 5 prepared by floating zone and flux methods exhibited a significant permittivity peak at T c % 750 K along the monoclinic b-direction. However, no research on BaTi 2 O 5 films has been reported in spite of their potential applications as ferroelectric actuators and devices.…”

Dielectric Properties of Ba<SUB>1&minus;<I>x</I></SUB>Ca<I><SUB>x</SUB></I>Ti<SUB>2</SUB>O<SUB>5</SUB> Prepared by Arc Melting

“…4,5) Recently, our research group 6) and Akishige et al 7) have independently synthesized single crystalline BT 2 and detected ferroelectricity in the b-direction. As single crystalline BT 2 has a high permittivity (20500) with a high Curie temperature (750 K), comparable to widely used PZT (Lead zirconium titanate), it is promising as a new lead-free high T c ferroelectric material.…”

A. C. Impedance Analysis on b-axis Oriented Ba1-xSrxTi2O5 Prepared by an Arc-Melting Method

“…21 Recently, our research group and Akishige et al independently discovered ferroelectricity of BT 2 and reported that single crystalline BT 2 has a high e r of 13000 to 30000 at the T c 750 K in the b-direction. 21 -25 We have also revealed that the crystal structure of BT 2 does not belong to a monoclinic C2m space group 26 but to a C2.…”

“…Since BT 2 shows the ferroelectricity only in the b-direction, the effect of foreign element on the dielectric properties of BT 2 should be usually studied on single crystalline specimens. Flux 25 and floating zone 21 melting methods have been employed to prepare single crystalline BT 2 . However it is difficult to prepare BT 2 single crystal in a large size.…”