High Acoustic Impedance Research Articles

Phase shift migration based plane-wave imaging of cortical bone

Cortical bone, a highly attenuated, anisotropic, and multilayered biological medium with high acoustic impedance, presents significant challenges for high-frequency ultrasound to penetrate its complex structure and acquire high-quality images. The traditional method of using uniform sound velocity in ultrasonic dynamic focusing imaging is limited by emission energy and frame rate, which hinders the accurate and rapid reconstruction of multi-layer structures and clinical applications. In order to meet these challenges, this study proposes a novel method, called the phase shift migration-based plane-wave bone imaging via velocity inversion (PSM-PW-VI), that can accurately and quickly image the multi-layer structure of cortical bone. In the PSM-PW-VI method, two identical linear array probes are arranged in parallel on both sides of the cortical bone for data acquisition. First, the ultrasound velocity distribution in the imaging region is obtained by using ultrasound travel time inversion. Next, two images corresponding to the upper probe and lower probe are acquired in parallel in the frequency domain by employing a phase shift migration-based coherent plane-wave compounding method. Finally, the two images are merged to generate a complete ultrasound image of the cortical bone. Wave propagation in cortical bone is simulated by using the open source toolbox <i>k</i>-wave in MATLAB. <i>Ex-vivo</i> experiments are conducted on 2.5-mm-thick sawbones phantom and 2.45-mm-thick bovine bone plates to evaluate the feasibility of the proposed method, by using the Verasonics platform. Simulation, phantom (Sawbones), and <i>ex-vivo</i> experiments validate the effectiveness of the method. Notably, the average error of the thickness is less than 0.2 mm, and the relative error is less than 7% for both three-layer and five-layer cortical bone. The influence of the number of plane wave compounding angles on imaging quality is investigated, revealing that only 15 angles are sufficient to produce high-quality images. The influence of the velocity model on imaging accuracy is also examined since accurate sound velocity estimation is crucial for obtaining high-quality images of cortical bone. Finally, the performances of PSM-PW-VI and PSM-SA in imaging depth and efficiency are compared. The results demonstrate that the proposed PSM-PW-VI method offers significant improvements in temporal resolution, data storage and processing quantity, emission energy, and imaging depth. The experimental findings validate the effectiveness of the proposed method as an accurate and efficient ultrasound imaging tool for cortical bone, and its substantial role in promoting ultrasound bone imaging technology and clinical applications.

Simulation and Optimization of Ultrasonic Transducer

The ultrasonic transducers have numerous applications in industries, including medical probes for performing ultrasound scans. One of the significant drawbacks of the ultrasonic transducer is the wastage of a large portion of energy, due to high acoustic impedance, while transmitting ultrasonic waves to the target object. The present study is aimed to investigate the material design of the piezo-composite transducer and improve its performance. Different piezo-composite transducers were simulated in the COMSOL environment by varying input parameters, and three key performance indicators (KPI) were calculated. Many constraint-based multivariable optimization algorithms have been used to maximize the KPIs. A set of parameters, such as Sensitivity and Fractional Bandwidth, have been found to increase the performance of piezo-composite transducer model and its overall efficiency. This study is intended to impinge unidirectional property to the transducer which is found to be beneficial in more accurate medical as well as structural reports and cost savings.

Design and Development of a Solar Electric Delivery Pod

The ultrasonic transducers have numerous applications in industries, including medical probes for performing ultrasound scans. One of the significant drawbacks of the ultrasonic transducer is the wastage of a large portion of energy, due to high acoustic impedance, while transmitting ultrasonic waves to the target object. The present study is aimed to investigate the material design of the piezo-composite transducer and improve its performance. Different piezo-composite transducers were simulated in the COMSOL environment by varying input parameters, and three key performance indicators (KPI) were calculated. Many constraint-based multivariable optimization algorithms have been used to maximize the KPIs. A set of parameters, such as Sensitivity and Fractional Bandwidth, have been found to increase the performance of piezo-composite transducer model and its overall efficiency. This study is intended to impinge unidirectional property to the transducer which is found to be beneficial in more accurate medical as well as structural reports and cost savings.

Research on the sensor for detection of carburized case depth based on nonlinear ultrasound

Carburized case depth may be characterized by using nonlinear ultrasound. However, the excitation and receiving sensors are difficult to control in the same conditions in each experiment and the operation process is complicated, therefore, a specialized sensor needs to be developed. In this work, the influence of the backing materials with different constituents and thickness on the characteristics of sensors is investigated. The structure of the specialized sensor is designed, applied, and verified in the detection of carburized case depth based on nonlinear ultrasound. The results show that the backing layer consists of three-dimensional graphene (3DG) 1wt%/tungsten powder 80wt%/epoxy resin has high acoustic impedance and attenuation characteristics, the backing layer with thicknesses of 8 mm has high sensitivity and residual vibration suppression, the specialized senor simplifies the detection procedure, and improves the efficiency and stability of detection.

AZ31B magnesium alloy matching layer for Lens-focused piezoelectric transducer application

Compared with planar transducers, focused transducers have higher ultrasound intensity and better lateral resolution in the focal zone. At present, the matching layer materials for focused transducers are mainly 0–3 composite materials, which have problems such as non-uniformity, difficulty to fabricate at high frequencies, and large sound attenuation. In this paper, finite element analysis is carried out to simulate lens-focused transducers with different matching layer structures and materials. It is found that the focused transducer with magnesium alloy matching layer has the best comprehensive performance. A lens-focused PZT-5H ultrasonic transducer was then fabricated with AZ31B magnesium alloy as the first matching layer. The measured results show that the center frequency of the transducer is 4.38 MHz, the −6-dB bandwidth is 68.35 % and the insertion loss is −13.88 dB. Benefiting from the high uniformity, high acoustic impedance and extremely low acoustic attenuation of magnesium alloy, the transducers in this research exhibit superior performances than other reported transducers with conventional matching layer. The current work suggests that AZ31B magnesium alloy is a promising matching layer material for ultrasonic transducers.

Progress towards wafer-scale fabrication based on gel casting technique for 1–3 randomised piezocomposite μUS linear array

Microultrasound (μUS) linear arrays operating at frequencies over 25 MHz have applications in high resolution biomedical imaging. 1–3 connectively piezoceramic – polymer composite (“piezocomposite”) material is attractive for fabrication of these devices due to its high effective electromechanical coupling coefficient and low acoustic impedance for better acoustic matching between transducer and tissue. However, a major concern with this type of material comes from interference between the fundamental thickness-mode resonance and spurious modes, which is usually generated by wave propagation and reflection within the repetitive and symmetrical structure of classical piezocomposite. In general, a fine spatial scale is required of the material structure to suppress the spurious modes; however, the fabrication process is challenging using standard dice-and-fill methods at the fine scales required for high frequencies. A promising way to overcome this challenge is to manipulate the lateral geometry and spacing of the piezoceramic pillars with a random distribution. In this work, gel casting in association with a micromoulding technique has been developed for manufacturing 1–3 randomised piezocomposite active material for μUS linear arrays. 48 vol% solid loading of piezoceramic powder with 30 wt% Hydantoin resin content was employed to prepare a low viscosity aqueous suspension. Through varying powder size, it was found that the suspension with 1.22 µm powder had the highest viscosity, ~ 0.47 Pa.s, and a short gelation time, ~ 10 mins. However, all suspensions had viscosities less than 1 Pa.s at a shear rate of 100 s−1, indicating that they had good flowability. The green body samples showed mean flexural strength 49.7 ± 2.49 MPa. After piezocomposite fabrication with randomised pillars, surface planarisation was used to obtain reliable edge definition of photolithographically-defined electrodes. 20-element arrays with 50-μm element pitch were configured using a bilayer lift-off process. The 1–3 randomised piezocomposite demonstrated its capability to minimise the effects of spurious modes in the thickness mode frequency range, while the thickness resonances provided k33 = 0.67. Without a matching layer, the array produced a − 6 dB bandwidth of 38.4%- and − 20-dB pulse length of 0.26 μs. These results show that 1–3 randomised piezocomposite fabricated from gel-casting associated with a micromoulding technique is feasible for fabrication of μUS linear arrays and may offer a route to small wafer-scale production.

Couplants in Acoustic Biosensing Systems.

Acoustic biosensors are widely used in physical, chemical, and biosensing applications. One of the major concerns in acoustic biosensing is the delicacy of the medium through which acoustic waves propagate and reach acoustic sensors. Even a small airgap diminishes acoustic signal strengths due to high acoustic impedance mismatch. Therefore, the presence of a coupling medium to create a pathway for an efficient propagation of acoustic waves is essential. Here, we have reviewed the chemical, physical, and acoustic characteristics of various coupling material (liquid, gel-based, semi-dry, and dry) and present a guide to determine a suitable application-specific coupling medium.

Double bottom simulating reflectors and tentative interpretation with implications for the dynamic accumulation of gas hydrates in the northern slope of the Qiongdongnan Basin, South China Sea

The origin of double bottom simulating reflectors (BSRs) and their relationship with gas hydrate systems are of great significance to the exploration of gas hydrate resources in submarine settings. Based on seismic data, this paper presents the first identified double BSRs in the northern slope of the Qiongdongnan Basin (QDNB), northern South China Sea. The imaged double BSRs are located in submarine ridges associated with a canyon system. These two BSRs (BSR1 and BSR2) are characterized by two subparallel high-amplitude reflections that mimic the seafloor’s distribution but have the opposite polarity. Patches of enhanced reflections (ERs) with high acoustic impedance indicate the occurrence of gas hydrate above BSR1 and between BSR1 and BSR2. The ERs indicate that the free gas terminates against BSR2 and is located beneath BSR2. The velocity spectrum of the strata shows that the interval velocity above the BSR1 and between BSR1 and BSR2 reaches as high as ∼2450 m/s, suggesting the presence of gas hydrates. The numerical modelling results of the gas hydrate stability zone (GHSZ) show that the geothermal gradient of the study area is 31.3–48.9 °C/km. Three potential formation mechanisms for these double BSRs are proposed: (1) variations in the P-T conditions in the GHSZ caused by erosion and redeposition associated with the submarine canyon; (2) precipitation of gas hydrates with different structures due to a supply of both thermogenic gas and biogenic gas; and (3) a relic paleo-BSR formed by the upward migration of a geothermal fluid through possible gas chimneys resulting in gas hydrate dissociation. BSR1 is correlated with the BGHSZ of structure I (SI) gas hydrates, and BSR2 may be correlated with the BGHSZ of structure II (SII) gas hydrates. Therefore, SI and SII gas hydrates may coexist in the study area, and SII gas hydrates and free gas may be present between BSR1 and BSR2. The occurrence of double BSRs suggests the dynamic accumulation of gas hydrates and free gas due to the erosion and redeposition of a submarine canyon, which shifted the BGHSZ and resulted in the differential distribution of the gas hydrates. A model illustrating the migration and accumulation of the hydrocarbons and gas hydrates associated with the occurrence of double BSRs is proposed, providing a reference for future gas hydrate exploration in the deepwater QDNB.

Seismic Constraints on the Trompsburg Layered Igneous Intrusion Complex in South Africa Using Two Deep Reflection Seismic Profiles

The discovery and characterization of layered intrusions around the globe have been predicated to a large degree on the imaging capabilities of the reflection seismic method. The ability of this tool to detect mineralization zones and structural controls such as faults and folds has been critical in unlocking the economic potential of igneous complexes, most notably the Bushveld Complex in South Africa. In this study, we present novel seismic constraints on the lesser-known Trompsburg Complex in South Africa. Two yet-unpublished seismic profiles were conducted end-to-end in the early 1990s, with a southwest-to-northeast trend through the centre of the ∼2,400 km2 Trompsberg potential field anomaly in South Africa, attributed to a 1915 ± 6 Ma buried layered intrusion complex. The complex was first detected by magnetic and gravity measurements near the town of Trompsburg in 1939 and was subsequently confirmed as a layered intrusion by borehole cores drilled thereafter. The combined length of the two profiles is 108 km. Both profiles have been reprocessed and interpreted to further constrain the subsurface expanse of the Trompsberg Complex along the seismic traverse. Processing and interpretation of the seismic profiles were aided by a handful of studies found in the literature: stratigraphy and physical property measurements of borehole cores that were drilled into the complex in the 1940s; pre-Karoo (∼317 Ma) lithological maps that were constructed based on boreholes in and around the investigation area; and potential field maps of the intrusion area near the town of Trompsburg. Most of the seismic reflection energy is concentrated within the top 1 km in both profiles, where localized reflectors with strong amplitudes are observed, due likely to the dolerite sills that permeate the Karoo cover. These sills obstruct seismic illumination of underlying structures due to their high acoustic impedance contrast with the surrounding soft rock sediments, rendering underlying reflections challenging to identify and enhance. The base of the Karoo is confidently identified to be at an average depth of 1.5 km and several reflection packages have been identified thereunder. These are linked to Proterozoic supracrustals associated with the Witwatersrand, Ventersdorp, Transvaal/Griqualand West, and Kheis Supergroups, as well as the Trompsburg Complex that intruded into them. The geometry of the Trompsburg Complex along the seismic traverse has been constrained with a moderate degree of confidence. It comprises a series of 30° northeasterly dipping reflectors near its southwestern boundary, flat reflectors near its centre at the town of Trompsburg, and 45° southwesterly dipping reflectors near its northeastern boundary. The lateral sub-Karoo extent of the complex is 60 km and its total thickness is difficult to constrain due to lack of deep reflections, but is likely between 6.6 and 7.5 km. The complex subcrops against the Karoo cover except near the southwestern region, where it is overlaid by Waterberg Group sediments.

Seismic inversion as a reliable technique to anticipating of porosity and facies delineation, a case study on Asmari Formation in Hendijan field, southwest part of Iran

Porosity and facies are two main properties of rock which control the reservoir quality and have significant role in petroleum exploration and production. Well and seismic data are the most prevalent information for reservoir characterization. Well information such as logs prepare adequate vertical resolution but leave a large distance between the wells. In comparison, three-dimensional seismic data can prepare more detailed reservoir characterization in the inter-well space. Generally, seismic data are an efficient tool for identification of reservoir structure; however, such data usable in reservoir characterization. Therefore, these two types of information were incorporated in order to obtain reservoir properties including porosity and facies in the study area. Using Multimin algorithm, petrophysical analysis was carried out for estimation of reservoir porosity. Then, an accurate post-stack inversion was accomplished to obtain the acoustic impedance volume. The results showed that the Ghar sandstone is characterized by a lower acoustic impedance compared to the high acoustic impedance Asmari Formation. Because of a relationship between acoustic impedance and reservoir properties (i.e., porosity), porosity cube calculation was performed by artificial neural network method which is a popular approach for parameter estimation in petroleum exploration. The consequences showed a good agreement between log based and seismic inversion-derived porosity. The inversion results and well logs cross-plots analyses illustrated that the Ghar member considered as a high quality zone with porosity 22 to 32 percent and the Asmari dolomite shows a low quality interval characters with porosity 1 to 6 percent. The findings of this study can help for better understanding of reservoir quality (especially porous Ghar member delineation) by lithology discrimination in the analysis of identification reservoirs and finding productive well location in Hendijan field.

Effect of interface thermal resistance on thermoelectric properties of acoustically mismatched composite

Composite materials can be promising to decouple electron and phonon transport for improved thermoelectric properties. Herein, the synergistic effect of the particle size of the dispersed phase and the interface thermal resistance (Rint) between the phases on the phonon thermal conductivity (κph) of the (1-x)La0.95Sr0.05Co0.95Mn0.05O3/(x)WC thermoelectric composite is demonstrated. The embedded WC, owing to its high electrical conductivity (σ), does improve σ of the composite. A high acoustic impedance mismatch between the phases results in a large Rint and lowers κph. Change in κph is further explained using theoretical analysis of Bruggeman asymmetrical model. The correlation between Rint and Kapitza radius is discussed to analyze the reduced κph. Synergistic effect of improved σ and lowered κph result in improved thermoelectric figure of merit (zT) of 0.20 at 463 K for (1-x)La0.95Sr0.05Co0.95Mn0.05O3/(x)WC composite. This study shows promise to design thermoelectric composites with the desired κph considering the elastic properties between the phases.

Use of heavy dielectric materials in solidly mounted A1 mode resonators based on lithium niobate

This paper discusses the applicability of dielectric materials with high acoustic impedance Z a for use in A1 Lamb mode solidly mounted resonator (SMR) with large electromechanical coupling coefficient k 2 . The study first shows that the use of metal as a reflector creates parasitic capacitance C p, which reduces k 2 significantly. Then, A1 Lamb mode SMRs are designed using HfN, HfO2, WN, WO3 etc., and achievable performances are compared. When either HfN, HfO2, WN, or WO3 is employed, relative large k 2 up to 25% is achievable. For further k 2 enhancement, a hybrid reflector configuration is also examined, wherein HfN is applied only to the top high Z a layer and W is applied to the others. The result indicates that C p caused by the W layers is still significant, and k 2 becomes worse in total.

3Pb1-3 Measurement of Acoustic Properties for Liquid Metal Couplers with Low Melting Point and High Acoustic Impedance

3Pb1-3 Measurement of Acoustic Properties for Liquid Metal Couplers with Low Melting Point and High Acoustic Impedance

Laser Peening with Solid-State Medium Having High Acoustic Impedance as Plasma Confinement Layer

Laser Peening with Solid-State Medium Having High Acoustic Impedance as Plasma Confinement Layer

Numerical and experimental analysis of a hybrid material acoustophoretic device for manipulation of microparticles

Acoustophoretic microfluidic devices have been developed for accurate, label-free, contactless, and non-invasive manipulation of bioparticles in different biofluids. However, their widespread application is limited due to the need for the use of high quality microchannels made of materials with high specific acoustic impedances relative to the fluid (e.g., silicon or glass with small damping coefficient), manufactured by complex and expensive microfabrication processes. Soft polymers with a lower fabrication cost have been introduced to address the challenges of silicon- or glass-based acoustophoretic microfluidic systems. However, due to their small acoustic impedance, their efficacy for particle manipulation is shown to be limited. Here, we developed a new acoustophoretic microfluid system fabricated by a hybrid sound-hard (aluminum) and sound-soft (polydimethylsiloxane polymer) material. The performance of this hybrid device for manipulation of bead particles and cells was compared to the acoustophoretic devices made of acoustically hard materials. The results show that particles and cells in the hybrid material microchannel travel to a nodal plane with a much smaller energy density than conventional acoustic-hard devices but greater than polymeric microfluidic chips. Against conventional acoustic-hard chips, the nodal line in the hybrid microchannel could be easily tuned to be placed in an off-center position by changing the frequency, effective for particle separation from a host fluid in parallel flow stream models. It is also shown that the hybrid acoustophoretic device deals with smaller temperature rise which is safer for the actuation of bioparticles. This new device eliminates the limitations of each sound-soft and sound-hard materials in terms of cost, adjusting the position of nodal plane, temperature rise, fragility, production cost and disposability, making it desirable for developing the next generation of economically viable acoustophoretic products for ultrasound particle manipulation in bioengineering applications.

Shock wave refraction patterns at a slow–fast gas–gas interface at superknock relevant conditions

Shock wave refraction theory and high-resolution numerical simulations were employed to predict the refraction pattern under superknock relevant conditions at slow–fast gas–gas interfaces which are characterized by a higher acoustic impedance in the incident phase than in the transmitted phase. First, our theoretical and computational methodologies were validated against results from the literature for planar shock–straight oblique interface interactions. Second, our framework was applied to planar shock-/cylindrical shock–cylindrical interface interactions. The theoretical regime diagram agrees well with the numerical predictions for the former configuration whereas significant discrepancies were observed for the latter. Numerical results show the formation of temperature and pressure peaks as the refraction structure transits from a free precursor refraction to a twin von Neumann refraction. This change in thermodynamic state can induce a significant reduction in ignition delay time, potentially leading to detonation onset.

Shallow seismic characteristics and distribution of gas in lacustrine sediments at Lake Erçek, Eastern Anatolia, Turkey, from high-resolution seismic data

The high-resolution analysis of single-channel, seismic reflection data from Lake Erçek (Eastern Anatolia) revealed a wide range of shallow gas anomalies consisting of enhanced reflections, seismic chimneys, acoustic blanking/acoustic turbidity, strong reflectors, and pockmarks, including both surface and buried pockmarks. The enhanced reflections are represented by the higher amplitude reflection patterns resulting from high acoustic impedance variations. They are mostly clustered in the NW-corner of the lake. Seismic chimneys are represented by vertical and thinned columnar disturbances of amplitude blanking and mostly occurred in deep basinal and faulted sections in the West and East of the lake. Some seismic chimneys, occurring together with pockmarks, represent vertical vent activations. Acoustic gas masking was represented by chaotic and diffuse seismic reflection patterns, including acoustic blanking and acoustic turbidity. As diffuse acoustic turbidity indicates gas-charged sediments, columnar disturbances showing acoustic blanking indicate degassing of the sediments. These features extend from SE to NW, coinciding with the deep basin morphology of the lake. A very local strong reflector was identified in the W-section of the lake, simulating the lake floor. This reflector is due to extended enhanced reflections, suggesting shallow free gas. Pockmarks observed in the lake are structurally classified into the two distinct types; surface (active) pockmarks found in the SE-part of the lake and buried (passive) pockmarks found in the NW. The former enlarge through deeper gas reservoir feedback, as the layering is impermeable, while the latter have resulted from a cessation of the reservoir feedback mechanism and/or permeable layering. In the lake, shallow gas distribution is controlled by faults, that provide the faulting-driven depositional control and earthquakes, that provide the seismicity-driven overpressure control. The shallow gas is then vertically–horizontally distributed and shaped by asymmetric depositional–stratigraphic factors. This study of Lake Erçek presents complementary information about a possible tectono-thermal origin of observed shallow gas.

Intelligent optimization design of 2–2 piezo-composites for ultrasonic transducer

2–2 piezo-composite material (PCM) with high electromechanical coupling coefficient and low acoustic impedance is a kind of common PCMs for fabricating piezo-composite ultrasonic transducer (PCUT). The performance of PCUT is obviously influenced by the design parameters (DPs) of 2–2 PCM, such as its thickness, kerf, and slice width. Combining the finite element analysis simulation and artificial intelligence methods, an intelligent optimization design method is proposed to optimize the DPs of 2–2 PCM to fabricate high-performance 2–2 PCUT. In the proposed method, the neural network models are trained by the simulation data to build up the relationship between the DPs and the performance of PCUT. Using the optimization criteria established based on the center frequency (CF), bandwidth (BW), and peak-to-peak voltage (PV), the modified particle swarm optimization algorithm is employed to determine the DPs of 2–2 PCM. The desired CF, BW, and PV are 4 MHz, 40% and 3.2 V, and the optimized thickness, kerf and slice width of 2–2 PCM are 376 µm, 69.6 µm, and 34.4 µm, respectively. Finally, the optimized 2–2 PCUT is fabricated based on the optimized DPs, and then characterized systematically. The optimized 2–2 PCUT exhibits a CF of 4.57 MHz, a BW of 41.6%, a PV of 2.89 V, and an electromechanical coupling coefficient of 0.71. The simulation and experiment results are consistent with the designed targets, which verifies the availability of the proposed method.

INVESTIGATION OF EFFECTS OF TUNGSTEN ON ACOUSTIC IMPEDANCE BY CALCULATING SOUND VELOCITIES FROM ELASTIC MODULUS APPROACH

Some metal filler powders, such as tungsten, are available as support materials in the bodies of ultrasonic transducers. The backing materials consist of two types of epoxy material, mainly hardener and adhesive, and filler powders. One of the reasons why these filler powders are incorporated into epoxy materials is the desire to achieve high acoustic impedance in ultrasonic probes. In this context, samples with different epoxy mixing ratios of tungsten added in amounts of 1, 2, 5 and 10 grams were prepared for the measurement, and the sound velocities used in the calculation of acoustic impedance were calculated over elastic modulus and densities measured by mechanical method. Thus, the effects of tungsten used in the support material in the probes of ultrasound devices were investigated. As a result, the increasing effect of tungsten on acoustic impedance was also determined with the calculations made by mechanical method.

Fabrication of a 3.5-GHz Solidly Mounted Resonator by Using an AlScN Piezoelectric Thin Film

In this study, a 3.5-GHz solidly mounted resonator (SMR) was developed by doping scandium in aluminum nitride to form AlScN as the piezoelectric thin film. Molybdenum (Mo) of 449 nm thickness and silicon dioxide (SiO2) of 371 nm thickness were used as the high and low acoustic impedance films, respectively, which were alternately stacked on a silicon substrate to form a Bragg reflector. Then, an alloy target with atomic ratio of 15% Sc was adopted to deposit the piezoelectric AlScN thin film on the Bragg reflector, using a radio frequency magnetron sputtering system. The characteristics of the c-axis orientation of the AlScN thin films were optimized by adjusting sputtering parameters as sputtering power of 250 W, sputtering pressure of 20 mTorr, nitrogen gas ratio of 20%, and substrate temperature of 300 °C. Finally, a metal top electrode was coated to form a resonator. The X-ray diffraction (XRD) analysis showed that the diffraction peak angles of the AlScN film shifted towards lower angles in each crystal phase, compared to those of AlN film. The energy dispersive X-ray spectrometer (EDX) analysis showed that the percentage of scandium atom in the film is about 4.5%, regardless of the sputtering conditions. The fabricated resonator exhibited a resonance frequency of 3.46 GHz, which was a small deviation from the preset resonance frequency of 3.5 GHz. The insertion loss of −10.92 dB and the electromechanical coupling coefficient of 2.24% were obtained. As compared to the AlN-based device, the AlScN-based resonator exhibited an improved electromechanical coupling coefficient by about two times.