Piezoceramic Materials Research Articles

About anomalous properties of porous piezoceramic materials with metalized or rigid surfaces of pores

The electromechanical properties of piezoelectric materials can be modified for some specific applications, e.g., hydrophone sensing applications, by incorporating a controlled porosity into them. This work investigates the effective moduli of a newly developed piezoelectric composite, fabricated using a novel approach, in which micro-and nanoparticles of specific metals or stiffer polymers were added to pore-forming agents and transported into ceramic matrices. This technique results in a porous piezocomposite with a metalized pore boundary. According to Newnham’s classification, it is a three-phase piezocomposite with connectivity 3–0–0. We considered a simple unit cell model composing of a cube of the piezoceramic material with a compound spherical pore at its center. The compound pore consists of a spherical vacuum pore and a spherical layer on its boundary. The spherical layer models the material deposited at the interface between the piezoceramic matrix and the pore. Based on the characteristics of this spherical layer, we studied porous piezocomposite with mechanically weak electrically conductive, mechanically hard dielectric, and mechanically hard electrically conductive pore surface. We assumed that this spherical layer is filled with a piezoelectric material. Very high dielectric permittivity moduli simulate the electrical conductivity, very high elastic stiffness moduli modulate the mechanical rigidity, while the piezoelectric moduli are negligible. We developed specific algorithms in ANSYS APDL to calculate the effective moduli of different composites understudy using the finite element method and the theory of effective moduli, considering the Hill–Mandel principle for energy conservation, under certain essential boundary conditions. Our simple unit cell model used for the main calculations was analogous to the model of the corresponding periodic composite. The findings of this basic model were also compared to a more complicated 3–0 random porosity composite model. We confirmed that the effective moduli versus porosity trends in both models are similar. We verified the numerical expectations by studying analytically the homogenization problem of an isotropic dielectric composite. The findings of this work confirm that the effective moduli of the developed piezocomposites significantly depend on the characteristics of material deposited between the piezoceramic and pore phases. The results of this study suggest that there may be several functional applications for these new piezocomposites.

LCD-SLA 3D printing of BaTiO3 piezoelectric ceramics

Stereolithography-based 3D printing is a promising method to produce complex shapes from piezoceramic materials. In this study, LCD-SLA 3D printing was used to create lead-free piezoceramics based on barium titanate (BaTiO3, BT). Three types of BT powders (micron, submicron and nanoscale) were tested in LCD-SLA 3D printing, and a technique for the preparation of a ceramic slurry suitable for LCD-SLA printing has been developed. Using TGA-DSC analysis, the thermal debinding parameters to obtain crack-free samples were determined, followed by further sintering and the study of the piezoelectric properties (εr = 1965, d33 = 200 pC/N, tan = 1,7 %). The results of the study demonstrate high potential for the production of complex piezoceramic elements that can be used in aviation, in particular, aviation radio equipment; in the marine industry for transceiver modules of hydroacoustic antennas; and in the nuclear industry for pressure control sensors in the steam–water path.

Design of wideband tonpilz transducers for underwater SONAR applications with finite element model

This paper describes the designing and optimization of tonpilz type transducers based on number of layers, width and thicknesses and type of active materials, dimensions of head and tail mass by exploiting finite element models for their effective and optimized usage in underwater SONAR applications. Geometry parameters of tonpilz transducers have been studied in terms of active piezoelectric stack and associated components comprised of head and tail masses and optimized structure is explored. Piezoelectric stack including piezoceramic material (PZT-4) and single crystal (PMNPT), is utilized for underwater acoustic generation, while Aluminum is taken as head mass and highly attenuated material stainless steel is used for tail mass. Performance of tonpilz transducer has been investigated and evaluated in terms of total radiating power (TRP), transmitting voltage response (TVR), directivity index and specific acoustic impedance for all designed structures. Comparison is carried out for the optimized structure that provides high sensitive frequency region in form of constant TVR and maximum sound directivity used for accurate under water detection applications. TVR in the sensitive region using PMNPT as the stack material shows enhanced results as compared to PZT-4. Sound intensity level in terms of TRP peaks also rises with a greater number of layers for both PMNPT and PZT-4 driving stack materials. Furthermore, it has been observed that Driving stack material is more effective than the other components of Tonpilz transducer because it effects the flat response and also enhances the TVR response. Secondly, head mass of the Tonpilz transducer is more effective than the remaining because resonance and flexural frequency depend on it.

Limits and Opportunities for Miniaturizing Ultrasonic Surgical Devices Based on a Langevin Transducer.

Minimally invasive surgery offers opportunities for reduced morbidities, faster postoperative recovery, and reduced costs, and is a major focus of surgical device innovation. For ultrasonic surgical devices, which offer benefits of high precision, low force, and tissue selectivity in surgical procedures, there exist laparoscopic ultrasonic shears for minimally invasive surgeries that combine tissue cutting with vessel hemostasis and sealing functions. Another approach to laparoscopy that could enable new procedures, and increase the sites of surgeries that could be reached by an ultrasonic device, involves integrating a miniature ultrasonic tool with a flexible surgical robot. However, miniaturization presents challenges in delivering the ultrasonic vibrational energy required to cut hard and soft tissues, partly due to the concomitant small volume of piezoelectric material. This article aims to provide insights into the trade-offs between transducer size, volume of piezoceramic material, resonance frequency, and the achievable displacement amplitude of devices that, consistent with current ultrasonic surgical tools, are based on a bolted Langevin transducer (BLT) and tip. Different configurations of BLTs are studied, including a cascaded version, simple bar versions, and BLTs with different front mass geometries. Results show that a BLT with a larger number of piezoceramic rings exhibits a higher coupling coefficient [Formula: see text] but with the compromise of a lower mechanical Q and stronger nonlinear response at increasing excitation levels. Displacement amplitude is reduced considerably when a BLT is excited at a higher harmonic, where the PZT rings are maintained at a nodal plane, and the resonance frequency shift at increasing excitation levels increases significantly. The electromechanical and dynamic characteristics of a cascaded transducer excited in its third longitudinal mode (L3) are almost equivalent to a much shorter version of a BLT driven at the same frequency but in its first longitudinal mode (L1), showing that a cascaded BLT can be a realistic proxy for studying the dynamics of small BLT devices. A new figure of merit is proposed that is the product of Q , [Formula: see text], and gain, which [Formula: see text] accounts for the gain of cylindrical BLTs which is shown not to be unity. It also proves effective as it incorporates the key factors affecting the achievable displacement amplitude of a BLT, including for BLTs with gain profiles in the front mass. The order of highest to lowest amplitude of a series of six gain-profile BLTs matches the order estimated by the figure of merit. It is shown that a BLT with a stepped profile front mass can achieve displacement that has the potential to cut hard or soft tissue and exhibits the smallest shifts in resonance frequency at increasing excitation levels.

Finite element model updating of piezoceramic thin-walled tube transducers

Despite routine usages of finite element (FE) analysis on designing piezoceramic transducers, building FE models for these transducers unfortunately might involve significant errors because the required piezoceramic material values provided by the manufacturers are often inaccurate. Using only a few characteristic quantities extracted from a measured impedance function of the transducer, this study develops a novel methodology for updating sensitive material parameters of a piezoceramic thin-walled tube transducer; both short- and open-circuit models are utilized. The effectiveness of the proposed methodology is demonstrated through two numerical examples, including both computer simulation and lab experiment.

Partial electrode method for loss and physical parameter determination of piezoceramics: Simplification, error investigation and applicability

The IEEE standard to determine physical parameters of piezoceramics has been utilized for decades by many researchers, yet it omits presence of important loss factors and possesses serious deficits that restrict accurate parameter determination. To resolve these issues, the partial electrode (PE) method was previously proposed, though the focus has been merely made on development of the method itself. In this study, we provide method simplification and more detailed analysis. The omission of unnecessary samples greatly boosts experiment and analysis process. To prove that the PE method is reliable, possible causes of errors were investigated; it is shown that they were either negligibly small or can be resolved with proper calibration. Furthermore, Applicability of PE method to various types of piezoceramic materials and compatibility with impedance analyzers are shown. Finally, PE method is proved to be reliable and can be alternative to IEEE Standard on Piezoelectricity.

МОДИФІКАЦІЯ ТА ПРАКТИЧНЕ ЗАСТОСУВАННЯ П’ЄЗОЕЛЕКТРИЧНИХ ПЕРЕТВОРЮВАЧІВ З РОЗДІЛЕНИМИ ЕЛЕКТРОДАМИ

В роботі наводяться результати удосконалення технології формування струмопровідних електродів п’єзоелектричних елементів та розробка пристроїв з п’єзоелектричної кераміки з розділеними електродами методом, що базується на технології комбінованої електронно-променевої модифікації. Показано перспективу використання методу термовакуумного напилення при отриманні покриттів електродів на виробах з п’єзоелектричної кераміки сорту ЦТС. Особливістю такого комбінованого методу є здійснення його в одному технологічному циклі «термовакуумне осадження – електронно-променева модифікація покриття» за незмінних умов робочого середовища, що виключає утворення хімічних сполук в осаджуваному покритті на проміжному етапі формування наноструктурних утворень. Встановлено, що утворені за запропонованою технологією срібні покриття на п’єзоелектричних елементах є більш рівномірними та однорідними порівняно з покриттями, отриманими у традиційний (промисловий) спосіб. Як практичний результат реалізації запропонованої в статті технології розроблено конструкції пристроїв п’єзоелектроніки на основі елементів із п’єзоелектричної кераміки зі сформованими на їх поверхні розділеними електродами, зокрема багатосекційного п’єзоелектричного перетворювача. Найбільш цікавим у цьому випадку є те, що п’єзоелемент (пружне монолітне тверде тіло) може одночасно мати різні властивості внаслідок технологічних можливостей методу термовакуумного напилення. Зміна розмірів електродів, їх взаємне розташування дають змогу впливати на параметри вихідних сигналів і відкривають широкі можливості для створення п’єзоелектричних перетворювачів для комп’ютерних систем критичного застосування. Основна перевага використання перетворювачів з п’єзокерамічних матеріалів у комп’ютерних системах пов’язана з їх особливою конструкцією, що дає можливість реалізувати принципово різні схеми в одному такому елементі.

Out-of-plane dynamic instability of nonlocal shear deformable nanoplates made of polyvinylidene fluoride materials subjected to electromechanical forces

Nowadays, piezoelectric materials are used as smart nanostructures in many engineering applications. Polyvinylidene fluoride (PVDF) is one of the piezoelectric polymeric materials which has fascinated the attention of the scientific community due to its remarkable properties. In the present study, dynamic stability and the parametric resonance of a Mindlin PVDF nanoplate lying on an elastic medium under electromechanical loadings and a moving nanoparticle are investigated. First, Hamilton's principle is used to obtain the partial equations governing the transverse oscillations of the PVDF nanoplate. By utilizing the theory of nonlocal piezoelasticity, the small-scale effects are applied to the equations. Navier’s approach is employed to procure the solution for the simply supported nanoplate. Then, the boundaries of instability in the plane of parameters are obtained by applying the energy-rate method to the governing time-varying ODEs. The results demonstrate that the increase in the nonlocal parameter and reduction of the nanoparticle movement path decrease the dynamic stability of the PVDF nanoplate. Also, the nanoplate made of PVDF materials is dynamically more stable than the nanoplate made of PZT-4 piezoceramic materials. Moreover, the piezoelectric voltage can be used to control the parametric resonance conditions of nanostructures. The results of this study have the potential to be utilized in the accurate design of nanoscale piezoelectric mass sensors in nanoelectromechanical systems.

Multifunctional sub-100 µm thickness flexible piezo/triboelectric hybrid water energy harvester based on biocompatible AlN and soft parylene C-PDMS-Ecoflex™

Nanogenerators have emerged recently as a new technology for harvesting energy from renewable and clean energy sources. Water in nature carries high amounts of kinetic and electrostatic energy; it is ubiquitous and widely accessible in different forms: i.e. as droplets, flows or waves. Either piezoelectric or triboelectric nanogenerators (PENGs, TENGs) have been shown to be effective for harvesting energy from liquids and ocean but the integration of both transduction mechanisms in a single hybrid device allows to exploit several operating conditions and to optimize performances, overcoming the limits of single components. Current piezo-tribo hybrid devices are mostly based on scarcely durable polymers or thick lead-based ceramic materials. Additionally, they are often limited to a specific application or environment due to their architecture and employed materials. In this work, a multifunctional, flexible and conformal hybrid nanogenerator (HNG) has been developed with a sub-100 µm thickness and with a novel combination of biocompatible thin-film piezo-ceramic and soft polymeric materials, for harvesting energy of different water sources, i.e. impacts, raindrops and buoying waves. The PENG component is based on a double-sided metallized AlN thin film, sputtered on polyimide. The TENG component is made of a metallized porous patch made of a mixture of PDMS and platinum-catalyzed silicone (Ecoflex™), encapsulated by a friction film of Parylene C surface-treated with UV/ozone. As a result, the HNG exhibits non-algebraic enhanced performances: the resulting power densities under tapping are ~ 6.5 mW/m 2 for PENG, 65 mW/m 2 for TENG, ~ 230 mW/m 2 for HNG. Multifunctionality is demonstrated by harvesting energy from different water-conveyed sources (i.e. impacts/breakwaters, raindrops, buoying waves). In particular, the device shows optimal and reliable energy harvesting performance under strong impulsive impacts (~ 0.8 W/m 2 ) and raindrops impacts (~ 9 mW/m 2 ). A custom buoyant device, called piezo-JellyFish (pJF), is proposed to exploit the HNGs for harvesting wave energy, based on a connection of three HNGs acting as oral arms: this system yields ~ 3.2 mW/m 2 , with 3 cm-amplitude standing waves. Finally, the HNG exhibits optimal adhesion on the skin and can be also used for monitoring human motions, revealing its multifunctionality also as a wearable conformal sensor. • The hybridization of piezoelectric and triboelectric nanogenerators is effective and allows to enhance performances. • A multifunctional, sub-100 µm thickness, flexible and conformal hybrid nanogenerator is developed for water energy harvesting. • The HNG is based on a novel combination of biocompatible thin-film AlN and soft parylene–PDMS–Ecoflex. • The HNG exhibits enhanced performances for tapping, impacts, raindrops and water waves, through a piezo-JellyFish system. • The HNG exhibits optimal skin-adhesion, revealing its multifunctionality as a wearable conformal sensor.

STRESSING ISSUE OF A PIEZOCERAMIC CANTILEVER WITH LONGITUDINAL POLARISATION AND ELECTRODE COATINGS

The main subject of this study is the investigation of the free vibration of a rectangular prismatic piezoceramic cantilever with longitudinal polarization and electrode coatings. Based on the general solution of coupled equations for piezoceramic material, applying the equations of electro-elasticity and satisfying electrical and mechanical conditions for the stress of a cantilever made from PZT4 piezoceramic material, componential displacements, electric potential, specific strain, electric field, and piezoelectric displacement, are determined and numerically obtained with Matlab software package. Based on the obtained equations and simulation results, it is possible to optimize the dimensions of the cantilever and determine the type of piezoceramic.

Effect of the Type of Sintering on the Dielectric Hysteresis of a Hard Piezoceramic Material based on Lead Zirconate Titanate

An experimental study is performed of the sintering technology effect of hard piezoceramic material PCR-8 has on its dielectric hysteresis. It is established that hot pressing and modifications of it allow the ferroelectric hardness of a piezoceramic material with a fixed composition to be varied, and the cost of the resulting piezoceramic products to be lowered by reducing energy expenses.

Development and characterization of novel piezoceramic material based stack actuator

The present research investigated the performance characteristics of multilayer stack actuator fabricated using the novel lead-free BaZr0.05Ti0.95O3 (BZT) piezoceramic material in the high field amplitude and low frequency dynamic regime. A systematic approach was undertaken, firstly, to experimentally study the electromechanical strain and degree of hysteresis of a single layer, and evaluate the dependency on the field amplitude and frequency. Based on the obtained characteristics of the single layer, a careful choice of the combination of field amplitude and frequency was implemented to study the free stroke of a multilayer stack actuator. The novel material based stack actuator fabricated at the laboratory scale yielded encouraging results for high precision actuatoric applications.

Homogenization of Porous Piezocomposites with Extreme Properties at Pore Boundaries by Effective Moduli Method

The article deals with problems on determining the effective moduli of porous piezoceramic materials with substances that have extreme properties and are deposited on the pore boundaries. The argumentation for the method of effective moduli is given. The reciprocity relation, from which the properties of effective moduli that are similar to known ones for moduli of piezoelectric materials can be obtained, is proved. It is noted that for homogenization of porous piezoelectric composites with rigid or electrode pore boundaries, it is necessary to use models for materials having extremely large moduli that are located on the pore boundaries. Using numerical calculations, anomalous properties of various effective piezoelectric moduli that are promising for practical applications of the investigated piezocomposites have been revealed.

Forced Axisymmetric Vibrations of an Electrically Excited Hollow Sphere Made of a Continuously Inhomogeneous Piezoceramic Material*

The forced axisymmetric vibrations of a hollow sphere made of a functionally graded radially polarized piezocelectric material are studied using the spatial theory of electroelasticity. The properties of the material vary continuously as a power function along the radial coordinate. The vibrations are excited by applying a varying electrostatic potential to the sphere surface. Solid and split electrodes are considered. After separation of variables and expression of the components of displacement and electric-flux density, electrostatic potential, and the stress tensor in terms of spherical functions, the original three-dimensional problem is reduced to a boundary-value problem for ordinary differential equations. The problem is solved by the effective method of discrete orthogonalization. The numerical solution is analyzed. Particularly, the distributions of the mechanical and electric parameters in the first modes of forced electroelastic vibrations of the sphere made of homogeneous and inhomogeneous piezoceramic materials are compared and analyzed. The effect of the loading caused by applying a variable electrostatic potential to the sphere surface on the distribution of forced vibration characteristics is studied.

Recent advances in flexible PVDF based piezoelectric polymer devices for energy harvesting applications

Energy harvesting is one of the most promising research areas to produce sustainable power sources from the ambient environment. Which found applications to attain the extensive lifetime self-powered operations of various devices such as MEMS wireless sensors, medical implants and wearable electronic devices. Piezoelectric nanogenerators can efficiently convert the vastly available mechanical energy into electrical energy to meet the requirements of low-powered electronic devices. Among the piezoelectric materials, poly (vinylidene fluoride) (PVDF) and its copolymers are extensively studied for the development of energy harvesting devices. Due to the outstanding properties such as high flexibility, ease of processing, long-term stability, biocompatibility makes them a promising candidate for piezoelectric generators. Nevertheless, compared to piezoceramic materials, PVDF based generators produce lower piezoresponse. Over the last decades, tremendous research activities have been reported to endorse the performance of PVDF based energy harvesters. This review article mainly focused on the recent progress in the performance improvement with processing methods, piezoelectric materials, different filler loading. The new developments and design structures will lead to an increase in piezoelectricity, alignment of dipoles, dielectric properties and subsequently enhance the output performance of the device. Electronic circuits play a vital role in energy harvesting to efficiently collect the developed charge from the device. Here, we have proposed a detailed description of the electronic circuits. Also, in the application part deals with the recent progress in flexible, biomedical and hybrid generators based on PVDF polymers.

ПЕРСПЕКТИВЫ МЕТОДОВ ИНТЕНСИВНОГО СПЕКАНИЯ ПЬЕЗОКЕРАМИЧЕСКИХ МАТЕРИАЛОВ

The paper investigates the possibility of changing the properties of piezoelectric ceramics for various purposes.The aim of the study is to correct properties by changing technological factors in the manufacture ofpiezoceramics without modifying their chemical composition. At the most important technological stage – sintering– the density, hardness and strength of piezoceramics are formed, which directly affect its electrophysicalparameters, since the piezoelectric effect is an Electromechanical transformation. Of particular interest are sinteringmethods that combine the process of compaction of particles with heating - hot pressing and spark plasmasintering. Such methods, due to the created uniaxial pressure, activate the diffusion processes of mass transferduring sintering, contributing to the production of high-density piezoceramics while lowering the sintering temperatures. However, unlike hot pressing, spark plasma sintering generates spark discharges between the powderparticles, which, in combination with ultra-fast heating (up to 1000 ° C/min), forms a fine-grained monophasestructure of ceramics. This microstructure increases the mechanical and electrophysical parameters of the resultingceramics. The aim of the study was to test the proposed sintering methods on piezoelectric materials of differentcompositions in order to control their properties. The objects of research were piezoceramic materials basedon the zirconate-titanate-lead system and their modifications, including multicomponent materials with high applicationpotential, as well as lead-free ferroelectric material Ba0.55Sr0.45TiO3 (BST). The dependences of theformed ceramic structure on the sintering method and temperature were determined using scanning electronmicroscopy. The regularities of "sintering method – microstructure – properties" are established. The effectivenessof hot pressing and spark plasma sintering methods for correcting the properties of piezoceramics of varioustypes of applications has been confirmed, which together with a decrease in sintering temperatures, as well as areduction in the duration of the process (by 36 times!) relevant for energy saving purposes.

Effective properties of a porous inhomogeneously polarized by direction piezoceramic material with full metalized pore boundaries: Finite element analysis

This paper concerns the homogenization problems for porous piezocomposites with infinitely thin metalized pore surfaces. To determine the effective properties, we used the effective moduli method and the finite element approaches, realized in the ANSYS package. As a simple model of the representative volume, we applied a unit cell of porous piezoceramic material in the form of a cube with one spherical pore. We modeled metallization by introducing an additional layer of material with very large permittivity coefficients along the pore boundary. Then we simulated the nonuniform polarization field around the pore. For taking this effect into account, we previously solved the electrostatic problem for a porous dielectric material with the same geometric structure. From this problem, we obtained the polarization field in the porous piezomaterial; after that, we modified the material properties of the finite elements from dielectric to piezoelectric with element coordinate systems whose corresponding axes rotated along the polarization vectors. As a result, we obtained the porous unit cell of an inhomogeneously polarized piezoceramic matrix. From the solutions of these homogenization problems, we observed that the examined porous piezoceramics composite with metalized pore boundaries has more extensive effective transverse and shear piezomoduli, and effective dielectric constants compared to the conventional porous piezoceramics. The analysis also showed that the effect of the polarization field inhomogeneity is insignificant on the ordinary porous piezoceramics; however, it is more significant on the porous piezoceramics with metalized pore surfaces.

Multifunctional flexible sensor array-based damage monitoring for switch rail using passive and active sensing

A passive monitoring technique for switch rails will be very attractive because it does not require extra excitations and can realize large area monitoring. However, complex wheel-rail interactions and sparse sensors will affect the accuracy of local damage identification. In contrast, an active monitoring technique has high local damage quantification ability but has low efficiency for large area monitoring. This study firstly presents a combination of piezoceramic material Lead zirconate titanate (PZT) wafers with accelerometers to configure a multifunctional sensor array that brings together active and passive monitoring mechanisms. The multifunctional sensor arrays are produced in a flexible form, which are adapted to complex geometry and are easy to install. In complementary passive monitoring, each sub area’s health state between 2 accelerometers is represented by reconstructing transfer functions, which are calculated from rail vibrations. The reconstructed transfer function in conjunction with principal component analysis (PCA)-based feature extraction is utilized for estimating the damaged sub area. Then accurate local damage identification can be realized through the active guided waves technique and correlation-based diagnostic imaging in conjunction with singular value decomposition (SVD). Simulation and experimental studies show the proposed mechanisms can identify the damaged sub area and basically extract damage locations with different lengths correctly with the sparse sensor array. Finally, based on a controlled experiment, the causes of the errors are evaluated and analyzed. The proposed mechanism can simplify data analysis, save monitoring time, and decrease the final cost.

New Efficient Technique for Finite Element Modeling of Macro Fiber Composite Piezoelectric Materials

A lot of interest to simulate piezocomposite actuators with finite element method has been increased recently. However, there are still open questions regarding the modeling methodology, accuracy, and computational time cost. In this work, a new technique for modeling macro fiber composite piezoelectric actuator by finite element analysis is proposed. The presented technique models the piezocomposite actuator as a simple monolithic piezoceramic material with just two electrodes along its longitudinal extremes instead of using the actual large number of electrodes which results in very fine finite element mesh with high computational time cost. The proposed technique is validated successfully by comparing its results with those of the actual detailed model as well as with the published experimental results and manufacturer’s data.

Experimental research on the acoustic transmission characteristics of refractory materials

The damage acoustic emission (AE) signal of refractories can be used to evaluate the classification and degree of the phase damage, which is different from the traditional damage location study in AE. In the analysis of AE signal, considering the nonuniformity of refractory inner structure, results of damage source inspection are usually affected by the signal transmission path. Therefore, the influence of transmitting path should be studied first. Piezoceramic material, capable of actuation and sensing, is commonly used to build AE probes. In this paper, two kinds of industrial refractories were selected as research objects and AE probes were chosen to generate emission acoustic signals. The relative amplitude attenuation coefficient and the relative energy attenuation coefficient were consequently designed as discriminant indicators to study the propagation characteristics of stress wave under different transmission paths and thicknesses. Results indicate that energy attenuation is higher than amplitude attenuation. Meanwhile, signal attenuation is principally proportional to transmission distance without directional selectivity. The above conclusions provide strong support to arrange AE sensors for nondestructive testing in refractory industry.