Characterization of the Elastic, Piezoelectric, and Dielectric Properties of Lithium Niobate from 25 °C to 900 °C Using Electrochemical Impedance Spectroscopy Resonance Method

Abstract

Lithium niobate (LiNbO3) is known for its high Curie temperature, making it an attractive candidate for high-temperature piezoelectric applications (>200 °C); however, the literature suffers from a paucity of reliable material properties data at high temperatures. This paper therefore provides a complete set of elastic and piezoelectric coefficients, as well as complex dielectric constants and the electrical conductivity, for congruent monocrystalline LiNbO3 from 25 °C to 900 °C at atmospheric pressure. An inverse approach using the electrochemical impedance spectroscopy (EIS) resonance method was used to determine the materials’ coefficients and constants. Single crystal Y-cut and Z-cut samples were used to estimate the twelve coefficients defining the electromechanical coupling of LiNbO3. We employed an analytical model inversion to calculate the coefficients based on a linear superposition of nine different bulk acoustic waves (three longitudinal waves and six shear waves), in addition to considering the thermal expansion of the crystal. The results are reported and compared with those of other studies for which the literature has available values. The dominant piezoelectric stress constant was found to be e15, which remained virtually constant between 25 °C and 600 °C; thereafter, it decreased by approximately 10% between 600 °C and 900 °C. The elastic stiffness coefficients c11E, c12E, and c33E all decreased as the temperature increased. The two dielectric constants ϵ11S and ϵ33S increased exponentially as a function of temperature.

Vibrational Spectra and Electro‐Optic Effect of Ferroelectric LiNbO3Crystal

“…The directly measured dielectric constants usually show strong frequency and temperature dependences in radio frequencies. [ 59,60 ] Alternatively, they can also be estimated from Raman spectrum by using the Lyddane–Sachs–Teller relations and [ 61 ] and correctly assigned observed phonon frequencies of LO and TO modes. One obtains and , which show much better agreement with our calculated results.…”

Ultrasonic Transducers for In-Service Inspection and Continuous Monitoring in High-Temperature Environments

“…However, it was shown that it may be overcome by operating at a high frequency (>MHz) and choosing a monocrystal or a stoichiometric element [ 16 ]. The complete set of elastic, piezoelectric and dielectric coefficients has been evaluated from room temperature to 900 C [ 17 , 18 ]. The selected material, 36 Y-cut LiNbO (from MTI Corporation), was chosen because its thickness vibration mode is quasi-extensional, with the geometry selected to ensure maximum resonance at the desired mode and minimal at other modes.…”

“…From a review of different electrodes for high-temperature sensors [ 21 ], platinum was selected and the supplier (INRS) offered to add a layer of titanium to ensure better adhesion of the platinum. The range of thickness for electrodes is around 100 nm, so 100-nm-thick platinum electrodes were deposited with a 20 nm titanium adhesion layer onto the piezoelectric element by physical vapor deposition and were usable up to 900 C [ 18 ]. The type of deposition selected was thermal and electron beam deposition.…”

Phononic crystals for Love waves based on thin-film lithium niobate

“…To verify the existence of SAWs on the LN-on-SiC composite substrate and to determine the operating frequencies of the designed device and phononic crystal, we investigated the mechanical wave distribution on the surface of the 0.3 µm thick LN film deposited on the SiC substrate. Material parameters (LN [50] and SiC [51]) are shown in supplemental information. The LN single crystal film is x-cut, with the direction of SAW propagation being in the y-direction of the crystal.…”