Deposition of orientation-controlled thick (K,Na)NbO₃ films on metal substrates by repeated hydrothermal deposition technique

摘要： (K,Na)NbO3 thick films were grown at 240°C on Ni-based metal substrates by repeated hydrothermal method. The metal substrates were covered with two types of buffer layers; SrRuO3/LaNiO3 and SrRuO3. Film thickness monotonically increased with increasing number of deposition cycles. The 27 μm-thick film was obtained on the metal substrate with SrRuO3/LaNiO3 by four cycles. The obtained films tended to show {100}c orientation and their degree of orientation increased with increasing number of deposition cycles. Films deposited on SrRuO3/LaNiO3-covered metal substrates showed more highly {100}c orientation compared with those on SrRuO3-covered metal substrates. Remnant polarization and coercive field measured at 5 kHz were 12 μC/cm2 and 70 kV/cm, while their effective values of piezoelectric coefficient (d33) was 35–40 pm/V for both films. These properties remained unchanged irrespective of a number of deposition cycles despite the orientation change of films. These results show that repeated hydrothermal deposition technique is one of the effective ways to prepare thick (K,Na)NbO3 films on metal substrates.