Interdependence of piezoelectric coefficient and film thickness in LiTaO₃ cantilevers

Abstract

Electromechanical energy demands homogenous thick films of piezoceramics with sufficiently large piezoelectric constant and reproducible performance. Single-phase LiTaO 3 films deposited by sol-gel processing have been fabricated as cantilevers to investigate the interdependence of dielectric and piezoelectric properties as a function of film thickness. Phase pure LiTaO 3 films with varying thickness in the range of 2.07-4.37 µm on stainless steel substrates were obtained after calcination of samples at Accepted Article This article is protected by copyright. All rights reserved 650 °C. The relative permittivity of optimized spin-coated films peaked at 479.73 (1 kHz), whereas the piezoelectric coefficient (d 33 mode) determined by piezo force microscopy was in the range of 21-24 pm/V. The effect of poling was studied through the butterfly and phase curves. A figure of merit up to 3.29 (10-18 m 2 /V 2) was determined for cantilever devices, which were able to generate a peak-to-peak voltage of 0.046-0.15 V using a 1 MΩ resistor as an impedance load at a fixed acceleration of 1.5 m/s 2. While the power density was in the range of ~ 4-20x10-9 W/m 3 , increased with the increasing film thickness. The leakage current density decreased in the range of 4x10-5-6x10-7 A/m 2 in the same direction. As both ferroelectric and piezoelectric properties of LiTaO 3 films are dependent on film thickness, an optimal energy conversion efficiency was obtained for a thickness of ~3 µm. Furthermore, these devices were tested up to a temperature of 150 °C for voltage generation. Given the need for lead-free piezoelectric materials for environmental applications, these LiTaO 3 cantilevers are very promising for vibrational energy harvester applications especially due to their cost effectiveness, small size, stability at higher temperatures, and repeatable properties which makes them suitable for MEMS devices for industrial applications.

Material strategies to enhance the performance of piezoelectric energy harvesters based on lead-free materials

“…The literature reports LiNbO 3 /LiTaO 3 films on the bottom electrodes containing heterostructures or metal substrates are rare. Recently, 2-4 µm thick LiTaO 3 films on stainless steel substrates were fabricated by means of sol-gel method and post thermal treatment for the vibrational EH applications and the reported generated PD by this heterostructure was 4-20 nW m −3 at acceleration of 1.5 g [163]. The c-axis textured films can be grown on the (111) Pt film electrodes.…”

Electron/hole piezocatalysis in chemical reactions

“…Other lead-free piezoceramics worthy of mention are Ba 0.7 Sr 0.3 TiO 3 , 43 molybdenum disulfide (MoS 2 ), 44 molybdenum diselenide (MoSe 2 ), 45 and lithium tantalate (LiTaO 3 ). 46…”

Expedient secondary functions of flexible piezoelectrics for biomedical energy harvesting

“…So far, flexible piezoelectric energy harvesters have been extensively reported to be fabricated from: (i) inorganic piezoelectric materials, including semiconducting nanowires (e.g., ZnO [ 3 , 20 ], GaN [ 21 , 22 ], CdS [ 23 ], InN [ 24 ], and ZnS [ 25 ]), lead-based (e.g., lead zirconate titanate (PZT) [ 26 ], PbZrO 3 [ 27 ], and PbTiO3 [ 28 ]) and lead-free ceramics thin films (e.g., BaTiO3 [ 29 ], LiNbO3 [ 30 ], (K,Na)NbO 3 (KNN) [ 31 ], and LiTaO 3 [ 32 ]); (ii) organic piezoelectric materials including synthetic polymers (e.g., poly(vinylidene fluoride) (PVDF) [ 33 , 34 ], poly(vinylidene fluoride-co-tri-fluoroethylene) (PVDF–TrFE) [ 35 ], nylon-11 (PA-11) [ 36 ], polylactic acid (PLA) [ 37 ], poly( l -lactide) (PLLA) [ 38 ], and poly( d -lactide) (PDLA) [ 39 ]), natural organics (e.g., amino acid [ 40 ], peptide [ 41 ], protein [ 42 ], and virus [ 43 , 44 ]), and molecular ferroelectrics [ 45 ]; and (iii) piezoelectric composites composing of conductive fillers (e.g., graphene [ 46 ], carbon nanotubes [ 47 ], and silver [ 48 ]), or non-conductive fillers (e.g., PZT [ 49 ], BaTiO 3 [ 50 ], KNN [ 51 ], ZnO [ 52 ], MgO [ 47 ], and TiO 2 [ 47 ]), and matrix (e.g., PVDF [ 49 ], P(VDF-TrFE) [ 47 ], hydroxyapatite [ 53 ], PDMS [ 51 ], and polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) [ 46 ]). Numerous studies have been dedicated to significantly improve the output power of flexible piezoelectric devices via materials engineering (e.g., texture/crystallinity enhancement [ [54] , [55] , [56] , [57] ], dipole/polarisation alignment [ 41 , 58 ], doping engineering [ [59] …”