Piezoelectric Charge Research Articles

Comparative study of the Bi(Ni0.5Zr0.5)O3-PbTiO3 and Bi(Mg0.5Zr0.5)O3-PbTiO3 piezoelectric materials for energy harvesters

ABSTRACT In this study, piezoelectric properties of 0.4Bi(Ni0.5Zr0.5)O3–0.6PbTiO3 (BNZ-PT) and 0.4Bi(Mg0.5Zr0.5)O3–0.6PbTiO3 (BMZ-PT) ceramics were investigated and compared with those of Pb(Zr,Ti)O3 in energy harvester applications. Their piezoelectric properties are comparable with those of Pb(Zr,Ti)O3 based materials, although they have lower lead contents. By optimizing the sintering temperature, the piezoelectric charge coefficients (d33) were improved to 438 and 351 pC/N for 0.4BNZ-0.6PT and 0.4BMZ-0.6PT, respectively, whereas the piezoelectric voltage coefficients (g33) were improved to 25.02 × 10−3∙V∙m/N and 28.37 × 10−3∙V∙m/N for 0.4BNZ-0.6PT and 0.4BMZ-0.6PT, respectively. The generated energies were estimated by measuring the generated output voltages. Generated energy densities of 1.67 and 1.01 mJ/cm3 were obtained from 0.4BNZ-0.6PT and 0.4BMZ-0.6PT, respectively. The optimum sintering conditions were found by observing the changes in the piezoelectric constant, dielectric constant, and density as a function of the sintering temperature.

Improved strain and transduction values of low-temperature sintered CuO-doped PZT-PZNN soft piezoelectric materials for energy harvester applications

In this study the low-temperature sintering effects and improved piezoelectric properties of CuO-doped 0.69 Pb(Zr0.47Ti0.53)O3-0.31[Pb(Zn0.4Ni0.6)1/3Nb2/3]O3 ceramics were investigated. At high temperatures, a sintered Pb(Zr,Ti)O3–Pb(Zn,Ni)NbO3 material has excellent piezoelectric properties such as a high piezoelectric charge coefficient (d33), high electromechanical coupling coefficient (kp), and high relative dielectric permittivity (εr). However, low-temperature sintering of functional ceramics is important for industrial device applications. For sensor applications, sintering or fabrication temperature is important because processing temperatures can interfere with process and material compatibility. Therefore, in this study, low-temperature sintering effects were investigated by employing low-temperature sintering aids while maintaining the piezoelectric properties. CuO was selected as the sintering aid for these applications. We will investigate and discuss the effects of the low-temperature sintering aid of CuO on the Pb(Zr,Ti)O3–P(Zn,Ni)NbO3 material in device applications. By employing the CuO dopant to Pb(Zr,Ti)O3–P(Zn,Ni)NbO3 material, the strain and transduction values were increased while reducing the sintering temperature.

Enhanced piezoelectricity and electromechanical efficiency in semiconducting GaN due to nanoscale porosity

Electrical polarization phenomena in GaN are important as they have significant impact on the operation of modern day energy efficient lighting and are fundamental to GaN-based high power and high frequency electronics. Controlling polarization is beneficial for the optimization of these applications. GaN is also piezoelectric, and therefore mechanical stress and strain are possible handles to control its polarization. Nonetheless, polar semiconductors in general, and GaN in particular, are weak piezoelectric materials when compared to ceramics, and are therefore not considered for characteristic electromechanical applications such as sensing, actuation and mechanical energy harvesting. Here, we examine the effect of nanoscale porosity on the piezoelectricity of initially conductive GaN. We find that for 40% porosity, the previously conductive GaN layer becomes depleted, and exhibits enhanced piezoelectricity as measured using piezoresponse force microscopy, as well as by using a mechanical energy harvesting setup. The effective piezoelectric charge coefficient of the porous GaN, d33,eff, is found to be about 8 pm/V which is 2-3 times larger than bulk GaN. A macroscale device comprising a porous GaN layer delivered 100 nW/cm2 across a resistive load under a 150 kPa mechanical excitation. We performed finite element simulations to analyze the evolution of the piezoelectric properties with porosity. The simulations suggest that increased mechanical compliance due to porosity gives rise to the observed enhanced piezoelectricity in GaN. Furthermore, the simulations show that for stress-based excitations, the porous GaN electromechanical figure of merit is increased by an order of magnitude and becomes comparable to that of barium titanate piezoceramics. In addition, considering the central role played by GaN in modern electronics and optoelectronics, our study validates a very promising research direction when considering stress-based electromechanical applications which combine GaN's semiconducting and piezoelectric properties.

Physical and mechanical properties of PVDF/KNN composite produced via hot compression molding

One of the most important lead-free piezoelectric compounds that has been studied extensively belongs to alkali niobate family, the sodium-potassium niobium (KNN) compound. In this study, KNN/PVDF composite was fabricated through hot compression molding of the components and its mechanical, thermal and electrical properties were studied. For this purpose, KNN was first synthesized by solid-state reaction during two-step calcination and its structural evolution was studied using XRD. Composite samples were prepared at different KNN to PVDF weight ratios. The powder mixture was then formed into disks by hot compression molding. The microstructure of the composite samples was investigated by SEM. The prepared samples were perfectly dense with a density in the range of 97.44% to 99.11% of the theoretical density. The thermal properties of the prepared composites were evaluated by thermogravimetric analysis and it was observed that final weight loss due to material degradation was reduced with increasing KNN weight percent. In addition, samples with higher KNN contents showed increased Young's modulus and yield strength values in compression. In order to investigate the electrical properties, the dielectric constant, dielectric loss factor, piezoelectric charge and voltage coefficients and electric polarization were studied. The results showed that the dielectric constant increased with KNN content. The same trend was observed in the piezoelectric charge coefficient and the dielectric loss factor of the PVDF/KNN composites. At 80 wt% KNN, the composite showed a distinct ferroelectric behavior with a remanent polarization of 0.255 μC/cm2 and 20.5 kV/cm coercivity. According to the results of the present study, hot compression molding is an effective method for producing KNN/PVDF composites with improved mechanical and thermal properties compared to its constituents.

Triboelectric and Piezoelectric Nanogenerators for Future Soft Robots and Machines.

SummaryThe triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) are two recently developed technologies for effective harvesting of ambient mechanical energy for the creation of self-powered systems. The advantages of TENGs and PENGs which include large open-circuit output voltage, low cost, ease of fabrication, and high conversion efficiency enable their application as new flexible sensors, wearable devices, soft robotics, and machines. This perspective provides an overview of the current state of the art in triboelectric and piezoelectric devices that are used as self-powered sensors and energy harvesters for soft robots and machines; hybrid approaches that combine the advantages of both mechanisms are also discussed. To improve system performance and efficiency, the potential of providing self-powered soft systems with a degree of multifunctionality is investigated. This includes optical sensing, transparency, self-healing, water resistance, photo-luminescence, or an ability to operate in hostile environments such as low temperature, high humidity, or high strain/stretch. Finally, areas for future research directions are identified.

Automatic Sorting System for Rigid Piezoelectric Transducer Wafers Used in Displacement Adjustment.

Piezoelectric transducer wafers are usually used in pairs to adjust the resonant cavity length of the ring laser gyro. In practice, the paired wafers are required to have similar piezoelectric charge coefficient d31. To handle the pairing operation in-batch, an automatic sorting system was developed on the basis of deformation measurement, which adopted a frame of a Cartesian-coordinate robot. The wafers were self-aligned in the vertical direction, and a vacuum holder was used to pick up, transfer, and then place them on thee testing desk one by one. The excitation voltage was loaded on the wafer by a specifically designed electrode, and the resulting micro deformation was measured by dual opposite inductive micrometers using the relative measurement principle. This particular electrode has the function of attitude self-adjustment and vacuum adsorption, which is conducive to loading the voltage reliably and protecting the wafer from undesired damage. Finally, the wafers were transported to different stock bins based on the measuring results. This system is suited to handle a mass of wafers by continuous processing on site for its high reliability and measurement consistency. The measurement accuracy, validated by laser interferometry, was better than 0.5 μm and the repeatability was superior to 0.1 μm.

Structural, linear and non linear optical, electrical, piezoelectric and thermal investigation on new semi-organic single crystal for microelectronics and high power laser applications: A brucinium di-hydrogen borate hydrate

Abstract The fine quality of brucinium di-hydrogen borate hydrate (BDHBH) single crystal was harvested from the saturation solution by slow evaporation technique. Crystal structure was solved by SHELEX program and which confirms that the title crystal belongs to monoclinic crystal system with non-centro symmetric space group P21. Linear optical parameters such as transparency range, cut-off wavelength, optical band gap, electro-negativity and refractive index of the title crystal were computed by UV–Visible study. The high surface laser threshold damage (SLDT) value shows its suitability in laser application coupled with high power output. Second order non-linear behavior was confirmed by Kurtz-Perry powder technique. The lesser value of FWHM shows the better quality of the grown crystal. Title compound is a utensil candidate for blue emission applications in field of optical device fabrications which is demonstrated by fluorescence optical study. The grown crystal exhibits RISE which is analyzed by Viker's micro hardness measurements. Dielectric study shows, the dielectric constant decreases exponentially by increasing frequency which confirms the normal dielectric performance and low dielectric loss indicates that, the lower concentration of defects in the title compound. Piezoelectric charge coefficient and piezo-voltage of BDHBH crystal were found to be 2 p C/N and 0.0175 p V m N−1 respectively. The multiple decomposition stages of the title compound were discussed in detail by various thermal analyses such as TGA, DTA and DSC.

Significantly improved dielectric and piezoelectric properties of BiAlO3 modified potassium bismuth titanate lead-free ceramics

The effects of BiAlO3 content on the crystal structure, microstructure, dielectric, and piezoelectric properties of (1-x)(K0.5Bi0.5)TiO3-xBiAlO3 (abbreviated as KBT-BA) (x = 0–0.05) ceramics were systematically studied. Rietveld refinement of XRD data revealed a decrease in tetragonality and an increase in weight fraction of the cubic phase with the increase in BiAlO3 incorporation. The frequency-dependent temperature of dielectric maximum (Tm) was found to increase from 351 °C for pure KBT to 372 °C (at 1 MHz) for 1% BA doped unpoled sample. An increasingly diffuse dielectric anomaly and strengthening of relaxor behavior were noticed in KBT-BA solid-solution with the increase in BA content. Temperature dependence of DC conductivity followed Arrhenius behavior, and the activation energies were found to be in 0.98 ± 0.03 eV to 1.18 ± 0.02 eV range for all compositions. The piezoelectric charge coefficient (d33) was found to be 109 pC/N for 5% BiAlO3 doped sample, which is ~ 80% higher than that of pure KBT.

Three-Dimensional MOF-Assisted Self-Polarized Ferroelectret: An Effective Autopowered Remote Healthcare Monitoring Approach.

In recent years, flexible and sensitive pressure sensors are of extensive interest in healthcare monitoring, artificial intelligence, and national security. In this context, we report the synthetic procedure of a three-dimensional (3D) metal-organic framework (MOF) comprising cadmium (Cd) metals as nodes and isoniazid (INH) moieties as organic linkers (CdI2-INH═CMe2) for designing self-polarized ferroelectret-based highly mechano-sensitive skin sensors. The as-synthesized MOF preferentially nucleates the stable piezoelectric β-phase in poly(vinylidene fluoride) (PVDF) and also gives rise to a porous ferroelectret composite film. Benefiting from the porous structure of 3D MOFs, composite ferroelectret film-based ultrasensitive pressure sensor (mechano-sensitivity of 8.52 V/kPa within 1 kPa pressure range) as well as high-throughput ( power density of 32 μW/cm2) mechanical energy harvester (MEH) has been designed. Simulation-based finite element method (FEM) analysis indicates that the geometrical stress confinement effect within the interpore region of the ferroelectret structure synergistically influences the mechano-electrical property of the MEH. In addition, 143 pC/N (∼4.5 times higher than commercial piezoelectric PVDF films) piezoelectric charge coefficient (d33) magnitude and superior response time (tr ∼ 8 ms) of this composite ferroelectret film enable the detection of different physiological signals such as coughing, pronunciation, and gulping behavior, making it a promising candidate for early intervention of healthcare, which may play a significant role in accurate alert of influenza and chronic obstructive pulmonary disease (COPD)-related symptoms. In addition, MEH enables the tracking of the subtle pressure change in the wrist pulse, indicating its usefulness in effective mechano-sensitivity. Since the cardiovascular signal is one of the vital parameters that can determine the on-going physiological conditions, the wireless transmission of the detected wrist pulse signal has been demonstrated. All of these features coupled with wireless data transmission indicate the promising application of MOF-assisted composite ferroelectret films in noninvasive real-time remote healthcare monitoring.

Effect of growth and residual stress in AlN (0002) thin films on MEMS accelerometer design

This paper discusses the growth and evolution of residual stresses in (0002) preferentially oriented aluminum nitride (AlN) layers on Si (111) wafers by sputtering technique for the development of micro-electro-mechanical system (MEMS) accelerometer. The microstructure of the deposited films exhibited vertical columnar structures. Residual stresses in the sputtered AlN films are − 1.2 GPa, − 0.8 GPa, and − 0.25 GPa for the film thickness of 600 nm, 750 nm, and 900 nm respectively. The effect of the residual stress on the piezoelectric MEMS acceleration sensor structure is analyzed. The presence of residual stress reduced the resonant frequency (up to 14.72%) and bandwidth (up to 27.3%) of the accelerometer. The locations of the von-Mises stress maxima are shifted from the beam edges (adjoining to the proof-mass) to the whole proof-mass area. The normalized stress sensitivity (which defines the piezoelectric charge sensitivity) is reduced by two orders due to the residual stress in the AlN layers.

A novel facile preparation method of self-polarized Poly(vinylidene fluorides) nanofiber for high-performance piezoelectric nanogenerator

A new facile preparation technique for self-polarization and alignment without external poling on poly(vinylidene fluorides) (PVDF) nanofiber was demonstrated. The nanofibers were prepared using a fast-centrifugal spinning technique. Formation of high-yield long, smoothed and beads-free fibers with enhanced piezoelectric β-phase was found to be a function of the ratio between solvents (N,N-Dimethylformamide (DMF) and acetone) and rotational speeds. Highest β-phase content and piezoelectric charge coefficient, d33 (95% and 152 pC.N−1 respectively) were achieved when DMF:acetone volume ratio and rotational speed were 3:7 and 8000 rpm, respectively. Under 17.8 kPa vertical stress, pure PVDF fibers-based flexible piezoelectric nanogenerator (PNG) displayed the highest output performances to date with open-circuit voltage, short-circuit current and power density of 22 V, 2.2 μA and 12.6 μW cm−2 respectively. Unique self-polarization characteristics of the fiber achieved via centrifugal spinning technique is the plausible explanation for the current highly durable and outstanding performance of the PNG.

Single-Layer MoS2 Mechanical Resonant Piezo-Sensors with High Mass Sensitivity.

Thin-film resonators and scanning probe microscopies (SPM) are usually used on low-frequency mechanical systems at the nanoscale or larger. Generally, off-chip approaches are applied to detect mechanical vibrations in these systems, but these methods are not much appropriate for atomic-thin-layer devices with ultrahigh characteristic frequencies and ultrathin thickness. Primarily, those mechanical devices based on atomic-layers provide highly improved properties, which are inapproachable with conventional nanoelectromechanical systems (NEMS). In this report, the assembly and manipulation of single-atomic-layer piezo-resonators as mass sensors with eigen mechanical resonances up to gigahertz are described. The resonators utilize electronic vibration transducers based on piezo-electric polarization charges, allowing direct and optimal atomic-layer sensor exports. This direct detection affords practical applications with the previously inapproachable Q-factor and sensitivity rather than photoelectric conversion. Exploration of a 2406.26 MHz membrane vibration is indicated with a thermo-noise-limited mass resolution of ∼3.0 zg (10-21 g) in room temperature. The fabricated mass sensors are contactless and fast and can afford a method for precision measurements of the ultrasmall mass with two-dimentional materials.

Piezotronic effect on Rashba spin–orbit coupling based on MAPbI3/ZnO heterostructures

Rashba spin–orbit coupling (SOC) is a core issue in semiconductor spintronics, which allows the manipulation of electron spin through an electric field rather than an external magnetic field, revealing a bright prospect for advanced electronic devices with ultra-high speed and integration. Conversely, the emerging piezotronic effect is the born characteristic for many semiconductors that have a non-central symmetric structure, such as ZnO and GaN. Here, we design three heterostructure devices, based on piezoelectric p-type (CH3NH3)PbI3 single crystals and n-type wurtzite-structured ZnO thin films, to theoretically study how the piezotronic effect can effectively work on the Rashba spin–orbit coupling. Benefiting from large piezoelectric charges at the interface when a vertical strain is applied, a high concentration of two-dimensional electron gas is induced in the plane of the heterostructure, which can tune the built-in electric field at the interface and further manipulate the Rashba SOC. With the increase in pressure, both the Rashba parameter and spin splitting are found to first vanish and then increase linearly for ZnO with doping densities of 1015 and 1016 cm−3. This work provides insight for manipulating electron spins via the introduction of piezocharges, showing great application potential of the piezotronic effect in tuning spintronic devices.

Crystal growth, structural, optical and piezoelectric investigations on novel B4AAT (bis-4-acetylanilinium tartrate): A phase matchable second and third-order NLO single crystal for optoelectronic and nonlinear optical device applications

Abstract A novel organic nonlinear optical crystal, bis (4-acetylanilinium) tartrate (B4AAT) has been synthesized and successfully grown by a slow evaporation method using acetone as a solvent at ambient temperature. The single-crystal X-ray diffraction study reveals that B4AAT crystallized into a triclinic system with the noncentrosymmetric space group (P1). The crystalline perfection of the grown crystal was affirmed by the High-resolution XRD study. The characteristic functional groups with vibrational assignments and molecular structure of B4AAT were confirmed through Infrared, Raman and NMR spectroscopic analyses. UV–Vis–NIR spectral analysis of the crystal shows 69% of transmittance with a lower cut-off wavelength at 334 nm. The grown crystal was thermally stable up to 143.39 °C. The laser-induced damage threshold of the B4AAT compound was found to be 15.78 GW/cm2 for 1064 nm Nd: YAG laser radiation. The grown B4AAT possesses the low value of dielectric constant and piezoelectric charge coefficient (d33 = 5.86 pC/N) for the supercapacitor and microelectronics industry. The size-dependent of second harmonic generation efficiency of the crystal was found to be 4.6 times higher than that of KDP. The photoluminescence and lifetime measurements of the molecules in the crystal were studied by Fluorescence spectral analysis. The third-order nonlinear optical activity estimated utilizing the Z-scan method reveals that the B4AAT possesses saturable absorption, negative nonlinearity with self-defocusing and optical limiting effect. The aforesaid results confirm that B4AAT crystal is a potential candidate for optoelectronic and nonlinear optical device applications.

Electrical properties, EPR analyses and defect chemistry of Mn-doped 0.675PMN-0.325PT piezoceramics

The morphotropic phase boundary solid solution of 0.675Pb(Mg1/3Nb2/3)O3-0.325PbTiO3 (0.675PMN-0.325PT) were studied. Manganese (Mn) was used as a dopant element in 0.4 mol% and 0.7 mol% ratios because of its multiple oxidation states. Sintering was done either in the air or under an oxygen-rich atmosphere. Both the effect of doping and sintering atmosphere on the electrical properties were reported. The ceramic with 0.4 mol% were exhibited higher properties such as piezoelectric charge coefficient (d33), dielectric constant, polarization values compared to undoped and 0.7 mol% Mn-doped ceramics. Electron paramagnetic resonance (EPR) spectroscopy was used to resolve the oxidation state of Mn in the 0.675PMN-0.325PT structure. The electrical properties were discussed and explained using defect chemistry.

All-in-one hybrid tribo/piezoelectric nanogenerator with the point contact and its adjustable charge transfer by ferroelectric polarization

The hybridization of tribo/piezoelectric nanogenerators (TPENG) has been verified as an efficient energy harvesting technique that utilizes both piezoelectric and triboelectric effects. Herein, we demonstrated a hybrid nanogenerator with a novel design of point contact that combined a BaTiO3(BTO)-based piezoelectric nanogenerator and a two-terminal triboelectric nanogenerator to make both piezoelectric and triboelectric effects appear during one successive cycle. In TPENG, BTO ceramic sheet and commercial PTFE film were selected as the piezoelectric and triboelectric layer, respectively. A small hole was created through the PTFE film, which acted as a conductive channel to transport piezoelectric charges. The unique structure facilitates the study of the interaction between triboelectric and piezoelectric charges by adjusting the direction of ferroelectric polarization of the BTO. The TPENG can generate a maximum voltage of 45 V and a current density of 10.4 μA/cm2 under an operating frequency of 2 Hz. The V-Q plot is employed to investigate triboelectric and piezoelectric effects from the perspective of output electrical energy, signifying that there is merely superposition of triboelectric and piezoelectric effect and no coupling between the triboelectric and piezoelectric charges for the TPENG with the point contact. The numerical analysis conducted by finite element simulation is consistent with the experimental results, demonstrating the rationality of the current experimental design. This work not only renders new insights into the understanding of piezoelectric and triboelectric effects in TPENG but also broadens the application prospects of Lead-free piezoelectric ceramics in energy conversion.

Measuring Piezoelectric Output-Fact or Friction?

Piezoelectric polymers are emerging as exceptionally promising materials for energy harvesting. While the theoretical figures of merit for piezoelectric polymers are comparable to ceramics, the measurement techniques need to be retrofitted to account for the different mechanical properties of the softer polymeric materials. Here, how contact electrification, including friction and contact separation, is often mistaken for piezoelectric charge is examined, and a perspective for how to separate these effects is provided. The state of the literature is assessed, and recommendations are made for clear and simple guidelines in reporting, for both sample geometry and testing methods, to enable accurate determination of piezoelectric figures of merit in polymers. Such improvements will allow an understanding of what types of material manipulation are required in order to enhance the piezoelectric output from polymers and enable the next generation of polymer energy harvester design.

High-performance piezo-phototronic multijunction solar cells based on single-type two-dimensional materials

Abstract Piezotronics and piezo-phototronics based on the third-generation semiconductor (such as ZnO, GaN, CdS, and monolayer chalcogenides) and two-dimensional materials, have attracted increasing attention due to the coupling characteristic of piezoelectric, photon excitation, and semiconductor properties. Strain can not only induce piezoelectric charges but also modulate bandgap of piezotronic materials. In this paper, we propose a structure of piezo-phototronic multijunction solar cell based on single-type two-dimensional piezoelectric semiconductor materials. By using the theory of detailed balance limit, the open circuit voltage and short circuit current of this piezo-phototronic multijunction solar cell are calculated. The results indicate that power conversion efficiency of the piezo-phototronic multijunction solar cell can theoretically reach to 33%, under the blackbody of temperature 6000 K, which is higher than the well-known theoretical Shockley-Queisser limit. This work provides guidance to design the next generation ultra-high performance piezo-phototronic solar cells.

Lead-free Na0.4K0.1Bi0.5TiO3 ceramic: Poling effect and enhancement in electromechanical and piezoelectric voltage coefficient

The effect of electric poling on the piezoelectric properties of the sintered Na0.4K0.1Bi0.5TiO3 is studied with varying poling field and temperature. An optimized poling condition (EP =50 kVcm, TP =110 °C) exhibited a high piezoelectric voltage (g33∼ 85 mV m/N) and charge coefficients (d33∼193pC/N). A combination of electric field induced irreversible transformation from polar nano regions embedded in a non-polar relaxor state to a long-range ordered ferroelectric state and increase in the structural ordering are responsible for the observed high piezoelectric properties. A mechanism is discussed to reveal the origin of high voltage coefficient due to poling, where the decrease of dielectric permittivity can facilitate high g33. This investigation provides an approach for designing the high performance Na0.4K0.1Bi0.5TiO3based materials suitable for sensors and energy harvesting applications.

Synthesis, Characterization, Photoluminescence and Piezoelectric Study of Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7

Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7 with the cubic pyrochlore structure were prepared at 1050 °C and 1400 °C using solid state reaction method. The crystal structure and unit cell parameters of powder samples were determined by X-ray diffraction method (XRD). Using TG/DTA thermal analysis, we determined the thermal behaviours of starting materials and Curie temperature of fine samples. Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7 have high Curie temperature at 770 °C and 765 °C, respectively. To determine morphological structure, elemental composition, photoluminescence properties, dielectric constant, loss tangent, and piezoelectric charge constant of Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7, scanning electron microscope (SEM), photoluminescence spectrophotometer (PL), LCR-meter and d33-meter were used. The results show that Dy1.98Yb0.02Ti2O7 and Lu1.98Er0.02Ti2O7 are multifunctional materials which show both photoluminescence properties and piezoelectric properties.