化学溶液法によるBa_2NaNb_5O_<15>薄膜の合成と評価(<小特集>化学的方法による機能性酸化物膜の合成)

抄録

Transparent and highly oriented Ba_2NaNb_5O_<15> (BNN) thin films have been prepared by using metal alkoxides. A homogeneous precursor solution was prepared by the controlled reaction between Nb (OC_2H_5)_65, NaOC_2H_5 and barium metal . The BNN precursor included a molecularlevel mixture of NaNb (OC_2H_5)_6 and Ba[Nb (OC_2H_5)_6]_2 in ethanol . The alkoxy derived powder crystallized to a low-temperature phase, and then transformed to orthorhombic BNN (tungsten bronze) at 600'C. BNN precursor films on substrates crystallized to orthorhombic BNN at 800℃ via the low temperature phase. The tungsten bronze phase of BNN thin films was confirmed by Raman spectroscopy. Highly(002) oriented BNN films of tungsten bronze structure were successfully prepared on MgO(100) and Pt(100)/MgO(100) substrates at 700℃ by using BNN underlayer. Transparent BNN thin films on MgO and fused silica substrates showed the absorption edge at 370 nm. The maximum of dielectric constant was observed at around 540'C . The remanent polarization and coercive field of the BNN film (thickness, 1.0μm) crystallized at 700℃ were 12.3μC/cm^2 and 101 kV/cm, respectively, at 123 K. BNN films on fused silica substrates exhibited second harmonic generation upon irradiation with 1064 nm light.