High yield preparation of (100)<i>_c</i>-oriented (K,Na)NbO₃ thick films by hydrothermal method using amorphous niobium source

Abstract

NbO 3 thick films were prepared at 240°C on (100) c SrRuO 3 //(100)SrTiO 3 substrates by hydrothermal method. Film thickness increased using an amorphous niobium source instead of conventionally used crystalline one and have the maximum thickness at 0.5 mmol of input mass of niobium source within the range of 0.02 7.5 mmol in case of the 20 h deposition. The yield of (K,Na)NbO 3 films from 0.5 mmol amorphous niobium source becomes 20 times higher than that from conventionally used a 2 mmol crystalline niobium source. In addition, crystal structure, surface morphology, dielectric constant, and ferroelectric and piezoelectric properties of these films were almost independent of the kinds of niobium sources and their input mass within the limitation of the present results.

Effect of film thickness on output power of a piezoelectric vibration energy harvester using hydrothermally synthesized (K,Na)NbO3 film

“…30) The KNN film thickness was varied within the range of 3.5-22.3 μm by changing the number of depositions. 31,32) The deposition temperature was 240 °C, and the other conditions were described previously. 29,35) After the hydrothermal process, the Pt top electrode was deposited on KNN//SRO//STO by electron beam evaporation.…”

“…29,30) Moreover, low-temperature deposition using the hydrothermal process allows the growth of thicker films due to smaller thermal strain. [31][32][33] In general, the thick film needs high voltage to align the direction of polarization by applying an electric field, called the poling process. 15) However, hydrothermally synthesized (K,Na)NbO 3 film has a self-polarized state in which the polarization direction is self-aligned, as discussed previously.…”

“…The controlled orientation by the selected substrate is ascertained to keep up to at least 100 μm in thickness. 31) We report on the film thickness dependence of the output power of an energy harvester using hydrothermally synthesized epitaxial (K 0.8 Na 0.2 )NbO 3 films (KNN) deposited on single-crystal SrTiO 3 (STO) substrates with SrRuO 3 (SRO) bottom electrodes and examined the potential application of orientationcontrolled thick KNN films to energy harvesting devices.…”

Effect of film thickness on piezoelectric vibrator using hydrothermally synthesized epitaxial (K0.88Na0.12)NbO3 film

“…[24][25][26][27][28] Among such materials, we focused on hydrothermally synthesized (K 0.88 Na 0.12 )NbO 3 films, which are reported to reach about 100 μm in thickness without cracking by repeating the deposition process. 29,30) Additionally, hydrothermally synthesized (K 0.88 Na 0.12 )NbO 3 films are reported to show relatively large e 31,f values and a selfpolarized state. [31][32][33] This self-polarization state allows us to avoid poling treatment, which is sometimes difficult for thick films due to the electrical breakdown that occurs when a large voltage is applied to poling treatment.…”

Alkali Niobate Powder Synthesis Using an Emerging Microwave-Assisted Hydrothermal Method

“…Sodium and potassium niobate K x Na 1− x NbO 3 (KNN)-based ceramics seem to be the most interesting piezoceramics to replace textured lead-based ones, the standard thanks to their highest piezoelectric features but causing an environmentally negative impact and human health unsafe behavior in use [ 4 , 5 , 6 , 7 , 8 ]. Ceramics based on KNN are secure from an environment point of view and show a promising combination of electro-mechanical properties and thermal stability [ 9 , 10 , 11 , 12 , 13 , 14 ]. However, the processing and sintering of such high-quality ceramics is still a challenge [ 15 ].…”