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SrBi2-xErxNb2O9 (x = 0.00, 0.02, 0.04, 0.06, abbreviated as SBN-xEr) multifunctional ceramics were prepared by solid-phase reaction method. Thermal annealing behavior shows that SBN-xEr ceramics have stable piezoelectric properties. For sample with x = 0.06, the piezoelectric constant d33 at 400 °C close to its Curie temperature retains 80% of its room temperature d33 value. Considering the luminescence characteristic of Er3+ ions, samples possess bright up-conversion photoluminescence performance with the strong green emission band at 550 nm and the weak red emission band at 670 nm under 980 nm laser source. Moreover, the electronic band structure of SBN-xEr ceramics was calculated using first principles. It is found that Er3+ doping causes the conduction band of samples to pass through the Fermi level and the valence band to be away from the Fermi level. The results suggest that SBN-xEr ceramics have good prospects in future luminescence and piezoelectric properties integrated devices.

In this study, a novel pre-synthesized Bi–Sb–O phase was produced and doped into the ZnO– Bi2O3– Co2O3– MnO2 (ZBCM)- based varistor to make an improvement in nonlinear coefficient (α) and a decrease in breakdown voltage (E1mA). Results showed that the ZBCM- Bi–Sb–O ceramics can be well sintered with high sintering density above 0.98 of the ZnO theoretical density at a low sintering temperature of 900 °C. A large average grain size (d) of 6.89 μm was obtained in the ZBCM – 3 wt% Bi–Sb–O varistor, which leads to a low E1mA of 235.0 V/mm. At the same time, the α increases to 53.0 due to the improved barrier height (ϕb) of 1.85 eV. Furthermore, the lowest dielectric loss (tanδ) at low frequency as well as the increased grain resistance (Rg) made the smallest leakage current density (IL) of 0.005 μA mm−2 in the same Bi–Sb–O doping content. Besides, a considerable low E1mA of 168.91 V/mm with a mildly α of 37.4 was obtained in the ZBCM– 1 wt% Bi–Sb–O varistor. Hopefully, this novel research provided a new strategy to prepare low-voltage ZnO– Bi2O3- based varistors at low sintering temperature.

In this work, a multifunctional lead-free (Bi0.5Na0.5)0.945Ba0.065Ti(1−x)(Fe0.5Sb0.5)xO3-0.005Er (BNBT-Er-xFS) ferroelectric material was prepared through the solid-state method, which has a large reversible field-induced strain of 0.465% (under an moderate electric field of 65 kV/cm) with a high normalized strain d33* (Smax/Emax) of 713 pm/V. Besides the excellent strain properties, this system also exhibits a bright green upconversion emission under excitation of 980 nm due to the luminescence characteristic of Er3+ ion. Moreover, the upconversion luminescence performance of BNBT-Er-xFS is enhanced with the (Fe0.5Sb0.5)4+ doping. At x = 0.0075, sample exhibited the strongest upconversion luminescence. As a multifunctional material, the BNBT-Er-xFS system is expected to be used in multifunctional electronic devices due to its excellent electrical and photoluminescence performance.

Multifunctional ferroelectric materials (1−x) (Bi0.5Na0.5)0.935Ba0.065Ti0.995(Er0.5Sb0.5)0.005O3-xLiNbO3 (BNBT-ES-xLN, x = 0, 0.015, 0.025, 0.030) were prepared through the method of conventional solid-state. The influence of LiNbO3 content on the field-induced stain and photoluminescence behavior was studied. The results showed that LN-doped BNBT-ES materials obtained a large reversible field-induced-strain of 0.35% (under an electric field of 80 kV/cm) with a high normalized strain d*33 (Smax/Emax) of 422 pm/V, at x = 0.025. BNBT-ES-xLN ceramics also exhibited a bright green up-conversion emission under excitation of 980 nm. Through the charge compensation mechanism and the increase of the transition probability between 4f electrons, the up-conversion luminescence performance of Er3+ is enhanced with the LN doping. The BNBT-ES-xLN system is expected to be applied for multifunctional electronic devices such as optical-electro integration and coupling device due to its excellent electrical and photoluminescence performance.

Dielectric properties of CaCu3Ti4O12 (CCTO) ceramics were studied by doping amount of Zr4+ donor on the basis of doping Y3+ donor. Ca0.97Y0.03Cu3Ti4-xZrxO12 (x=0, 0.005, 0.010, 0.015, CYCTZO) ceramics were prepared by reaction sintering method, and the phase structure, microstructure and dielectric properties of the ceramics were studied. The single phase CCTO was detected in all ceramic samples. SEM images of samples showed a high density and uniform-sized microstructure, and the average grain sizes of the ceramics was reduced with increasing content of Zr4+ donor. Interestingly, the dielectric constant (εr) was increased significantly while the dielectric loss tangent (tanδ) was decreased with the suitable doping amount of Zr4+. CYCTZO ceramics with x=0.010 exhibited a relatively high εr value of 1.02×105 at 1kHz. Meanwhile, the improved grain boundaries response and dielectric properties were closely related to the strengthened grain boundaries resistance (Rgb). The present results indicate that the εr was improved and the tanδ was reduced by doping Zr4+ donors in Ca0.97Y0.03Cu3Ti4O12 (CYCTO) ceramics and explained that the electrical properties were closely related to the electrical heterogeneity of ceramic grains and grain boundaries.

Graphene modified nanostructured Al2O3/TiO2 coatings were prepared on 316L stainless steel by plasma spraying. The microstructure of feedstocks and coatings was characterized using X-ray diffraction and scanning electron microscope. The bonding strength of the coatings was studied by dual tensile tests. The Vickers hardness of the coatings was used in this paper. The wear resistance of the coatings was demonstrated by sliding wear tests. The coatings containing 6 wt% graphene shows excellent wear resistance, of which the porosity is 35% lower, the bonding strength is 62% higher, and the wear rate is 20–25% lower than that of the non-graphene coatings. In addition, there is no obvious effect on the hardness of the coatings with the addition of graphene.

Pr3+-modified SrBi4Ti4O15 ceramics were prepared using a conventional solid-state reaction method. The modified ceramics simultaneously exhibited both visible photoluminescence and enhanced electrical properties. In visible light, ceramics exhibited a strong red emission peak at 610 nm corresponding to the inter-4f transition 1D2 → 3H4 due to the absence of inversion symmetry at Pr3+ sites. This red luminescence is greatly potential in various display devices. Meanwhile, samples modified by Pr3+ in x = 0.002 showed a large piezoelectric constant of 20pC/N and a remnant polarization of 22.78 μC/cm2, as well as a high Curie temperature value of 511 °C and excellent piezoelectric temperature stability. Moreover, the Pr3+-modified SrBi4Ti4O15 ceramics show a fatigue-free polarization behavior. All these advantages may expand the application fields of the materials as multifunctional devices by integrating their luminescent and piezoelectric properties.

Ta-doped Bi3.25La0.75Ti3O12 (BLTT) ferroelectric thin films were prepared via rf-magnetron sputtering with subsequent annealing treatments. The crystallization evolution and ferroelectric behavior of BLTT thin films were studied using in situ high temperature X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM) and piezoresponse force microscopy (PFM). With the increase of annealing temperatures, the thin films exhibited a preferred 〈117〉 crystalline orientation first and then weakly crystallizations to c-axis were obtained at high temperatures. SEM analysis reveals that the grain growth might be performed by melting and combining of particles in surface layer of original grains. PFM phase images reveal that less domain switching could be induced for BLTT films with larger grains.

(1-x) (Bi0.5Na0.5)0.935Ba0.065TiO3-xSrSmAlO4 (BNBT6.5-xSrSmAlO4) lead-free ceramics were prepared through the solid reaction sintering method. The phase structure, electrical and photoluminescence properties of the ceramics were systematically studied. Substitution with SrSmAlO4 induced the transition of coexisting ferroelectric rhombohedral-tetragonal phases to the relaxor pseudocubic phase. This transition was accompanied by the drastic disruption of ferroelectric order and the enhancement of electric-field-induced strain. The BNBT6.5-xSrSmAlO4 ceramics prepared with the dopant concentration of x = 0.012 exhibited a large unipolar strain of 0.41% and a correspondingly large signal piezoelectric d33* constant (= Smax/Emax) of 512 pm/V. Moreover, the SrSmAlO4-modified ceramics prepared in this work exhibited strong orange red emission upon excitation with blue light. The emission intensities of the ceramics were dependent on dopant concentration. The ceramic with the dopant concentration of x = 0.012 demonstrated the strongest emission. It also showed a weak green emission peak at 564 nm that corresponded to the 4G5/2→6H5/2 transition and two strong red emission peaks at 599 and 646 nm that corresponded to the 4G5/2→6H7/2 and 4G5/2→6H9/2 transitions, respectively. These results suggested that the BNBT6.5-xSrSmAlO4 system has multifunctional characteristics and considerable potential applications in novel devices with multiple functions given its excellent integrated luminescence and electrical properties.

This work presents the microstructure and electrical properties of MnO-doped SnO2–Zn2SnO4 ceramic composites prepared through conventional ceramic processing. Scanning electron microscopy images reveal that all samples have a compact structure. With increasing MnO content, the grains grow larger and the grain boundaries become unsharp. Energy dispersive spectroscopy results for the sample doped with 0.1 mol% MnO indicate that Mn distributes randomly on the grain surfaces. X-ray diffraction patterns exhibit that all the samples are composed of SnO2 and Zn2SnO4, and the relative intensity of the diffraction peak for Zn2SnO4 increases with increasing MnO content. The relations between the electric field and current density show that all the samples have varistor properties. For the samples doped with 0.2 and 0.3 mol% MnO, the breakdown electric field is so large that it exceeds the measuring range of the instrument, whereas the relative permittivity is as low as about 30 at 100 Hz. In the electric modulus spectra, two sets of relaxation peaks were observed and the corresponding activation energies are enhanced greatly by doping MnO. The effect of MnO on the microstructure and electrical properties indicates that the space charges trapped by oxygen vacancies are the origin of the great permittivity and varistor properties for SnO2–Zn2SnO4 ceramic composites.

This work presents $$\hbox {Bi}_{{2}}\hbox {O}_{\mathrm {3}}\hbox {-doped SnO}_{{2}}$$ ceramic varistors prepared through conventional ceramic processing in the sintering temperature range of 1290–1320°C. The sample sintered at 1300°C exhibits a breakdown electric field as low as 11.6 V $$\hbox {mm}^{\mathrm {-1}}$$ . Scanning electron microscopy images reveal that all the samples have a compact structure, and energy dispersive spectroscopy results for the sample sintered at 1300°C indicate that Bi distributes homogeneously along the grain boundaries and aggregates inhomogeneously on the grain surfaces. With increasing sintering temperature, the grain boundary barrier height remains nearly constant at 0.80 eV. In both the dielectric loss and electric modulus spectra of the sample sintered at 1300°C, obvious relaxations were observed and the activation energies obtained from the respective spectra were 0.33 and 0.15 eV, which are expected to be related to oxygen vacancies and interstitial ions, respectively. Complex impedance spectra are employed to develop a non-typical equivalent circuit model for the $$\hbox {Bi}_{{2}}\hbox {O}_{\mathrm {3}}\hbox {-doped SnO}_{{2}}$$ ceramic varistors at low voltage that yields an excellent fit to the data.

Highly epitaxial 0.755(Bi0.5Na0.5)TiO3-0.065BaTiO3-0.18SrTiO3 (BNT-BT-ST) ferroelectric films with (100), (110) and (111) orientations were fabricated on Nb doped SrTiO3 (N-ST) substrates. Three patterns of microstructure morphologies are observed in the epitaxial thin films. The superior ferroelectric with remanent polarization Pr of 18 µC/cm2 is obtained in (100) oriented thin film. The excellent dielectric properties with highest dielectric constant (1170) and tunability (68%) exhibit in the (111) oriented thin films. Both of the ferroelectric and dielectric properties in the epitaxial BNT-BT-ST films are more remarkable than those of the polycrystalline BNT-BT-ST film. The results should be ascribed to the orientated microstructure and ferroelectric-to-relaxor transition observed in the epitaxial BNT-BT-ST thin films. Strong orientation dependences of microstructure and electric properties are due to the relative alignment of crystallites and anisotropic polarization rotation. This study provides an insight into how to utilize orientation to regulate the structure and properties of epitaxial thin films.

Ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films were deposited on Pt(111)/Ti/SiO2/Si substrates at 400 °C using rf-magnetron sputtering method. The microstructures were studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometer. The as-deposited thin film is amorphous, while transformed to microcrystalline and well crystalline states after annealing at 650 °C and 750 °C, respectively. After annealing at 750 °C, the polycrystalline BLT thin film showed plated-like grains all with (117)-preferred orientation. Analyses of ferroelectric properties indicated that, comparing with the as-deposited thin film, the highly (117)-oriented crystalline thin film exhibited well-saturated hysteresis loops with a superior remnant polarization (2Pr) of 30.7 μC/cm2.

Lead-free perovskite (Bi0.5Na0.5)0.935−xPrxBa0.065Ti1−xSbxO3 (BNBT6.5–xPS) ceramics are prepared by ordinary sintering technique. The compositional dependence of phase structure, electrical and photoluminescence properties of the ceramics was systematically investigated. Results showed that all samples exhibit pure perovskite structure with dense microstructures. With the addition of PS, a strong red emission located at 610 nm and a weak red emission at 660 nm under a light 450 nm excitation was observed. The strong red emission band is ascribed to the inter-4f transition from the excited 1D2 to the ground state 3H4 and the weak red emission located at 660 nm is due to the 3P0 → 3F2 transition. And then the BNBT6.5–0.004PS ceramic exhibited the strongest photoluminescence property. Besides the excellent photoluminescence properties, PS modifications induced an enhanced filed-induced strain. At x = 0.001, a large strain of 0.31% was obtained at a driving field of 70 kV/cm. As a multifunctional material, it has potential application as a multifunctional device such as optical-electro integration and coupling device applications.

The variations of XRD full width at half maximum (FWHM), residual stress and hardness for the surface of GCr15 steel after triple shot peening (TSP) as a function of annealing time and temperature are studied. The results show that with the increase of annealing temperature and time, hardness and FWHM increase gradually while compressive residual stress (CRS) decreases gradually. CRS and micro- structure work together on the hardness values, and the micro-structure is the most important factor for hardness. According to establishing the quantitive relationship of hardness with FWHM and CRS, the value of hardness can be calculated; a new type of noncontact and nondestructive hardness testing can be realized by XRD method.

Piezoelectrics have shown great potential for controlling the piezoelectro-optical process in multifunctional materials. Electric field poling is an effective way of modulating the structure of rare earth doped piezoelectric materials, thus affecting their piezoelectro–optical interplays. Here, the (Ba0.96Ca0.04)(Ti0.90Sn0.10)O3-0.2%Sm (BCST-Sm) lead-free ceramics exhibit high piezoelectric properties (d33 = 450 pC N−1, kp = 52%) as well as strong reddish-orange photoluminescence emission (PLE). The highest piezoelectric coefficient and PLE quenching of the BCST-Sm ceramics are obtained simultaneously at a poling electric field of 20 kV cm−1, which are related to the phase transition and the changes in lattice symmetry and domain structure. The BCST-Sm ceramics transform from the coexisting R–T phases to a single T phase by applying an electric field, where the long-range ordered large domain structure is induced. The decreased asymmetry and relaxor and the increased domain size contributed to the quenching of photoluminescence (PL) performance, while the instability of the polarization state and domain reorientation benefitted the piezoelectric response. This work demonstrates the inherent piezoelectro–optical interplays in association with various structures stimulated by the electric field and provides a physical mechanism for better understanding and designing multifunctional materials.

Lead-free ceramics, SrBi2Nb2O9–xBi2O3 (SBN–xBi), with different Bi contents of which the molar ratio, n(Sr) : n(Bi) : n(Nb), is 1 : 2(1 + x/2) : 2 (x = −0.05, 0.0, 0.05, 0.10), were prepared by conventional solid-state reaction method. The effect of excess bismuth on the crystal structure, microstructure and electrical properties of the ceramics were investigated. A layered perovskite structure without any detectable secondary phase and plate-like morphologies of the grains were clearly observed in all samples. The value of the activation energy suggested that the defects in samples could be related to oxygen vacancies. Excellent electrical properties (e.g., d33 = 18 pC N−1, 2Pr = 17.8 μC cm−2, ρrd = 96.4% and Tc = 420 °C) were simultaneously obtained in the ceramic where x = 0.05. Thermal annealing studies indicated the SBN–xBi ceramics system possessed stable piezoelectric properties, demonstrating that the samples could be promising candidates for high-temperature applications.

Lead-free (Ba1−xCax)(Ti0.95Hf0.05)O3 (x = 0.04–0.14) (BCHT) ceramics with good piezoelectric properties were successfully prepared using solid state reaction method. The structural and electrical properties of the BCHT ceramics were systematically studied. The polymorphic phase transitions (PPT) from orthorhombic phase to tetragonal phase shifts towards low temperature with increasing Ca contents, and the PPT can be obtained at room temperature (RT) in the composition range of 0.08–0.10 for the BCHT ceramics. The tetragonality of the BCHT ceramics at PPT is increased after poling treatment as depicted in the XRD patterns and Raman spectroscopy. The BCHT ceramics at x = 0.08 exhibit good piezoelectric properties (d33 = 380 pC/N, kp = 50% and Smax = 0.19% under the applied electric field of 50 kV/cm) and ferroelectric property (Pr = 13.4 μC/cm2), due to the coexistence of tetragonal phase and orthorhombic phase. The aging rate of d33 values from 20 °C to 90 °C is lower than 20% in this work, indicating that the BCHT ceramics have good temperature stability. The high piezoelectric properties with good temperature stability indicate that the BCHT ceramics are promising candidates as lead-free piezoelectric ceramics.

Ho 3+ -modified SrBi 4 Ti 4 O 15 ceramics with bright green light emission and enhanced electrical properties were fabricated by a conventional solid-state reaction method. Upon visible light irradiation, samples exhibit a strong green emission located at 546 nm and a weak red emission at 653 nm. These two emissions corresponding to the intra f - f transition from the excited state 5 S 2 to the ground state 5 I 8 and the 5 F 5 → 5 I 8 transition of Ho 3+ , respectively. The relative intensity of green and red emissions is related to the Ho 3+ contents closely, due to the concentration quenching effect. Moreover, it is also found that Ho 3+ doping significantly enhanced the electrical properties. At x = 0.008, samples exhibit optimal electrical properties and excellent piezoelectric temperature stability for the SBT- x Ho system. These results reveal that these materials have good application prospect in future optical temperature sensors by integrating its luminescent and piezoelectric properties.

Lead–free piezoelectric ceramics (1−x)(Bi1/2Na1/2)0.935Ba0.065TiO3−xCaYAlO4 (BNBT6.5−xCYAO) were prepared using a conventional solid sintering technique. The addition of CYAO destroyed the ferroelectric long–range order with the shift of the ferroelectric–relaxor transition temperature TF–R down to room temperature and induced the appearance of ergodic relaxor phase. Thus, it leads to a giant field–induced strain with a peak value of 0.44% at x = 0.012.

Lead-free piezoelectric ceramics (Bi0.5Na0.5)0.935Ba0.065Ti1−x (Ni0.5Sb0.5) x O3 (BNBT6.5-xNS) have been fabricated using conventional solid sintering technique. The effect of (Ni, Sb) doping on the phase structure and electrical properties of BNBT6.5 ceramics were systematically investigated. Results show that the addition of (Ni, Sb) destroyed the ferroelectric long-range order of BNBT6.5 and shifted the ferroelectric–relaxor transition temperature (T F–R) down to room temperature. Thus, this process induced an ergodic relaxor phase at zero field in samples with x = 0.005. Under the electric field, the ergodic relaxor phase could reversibly transform to ferroelectric phase, which promotes the strain response with peak value of 0.38% (at 80 kV/cm, corresponding to d 33 * = 479 pm/V) at x = 0.005. Temperature-dependent measurements of both polarization and strain confirmed that the large strain originated from a reversible field-induced ergodic relaxor to ferroelectric phase transformation. The proposed material exhibits potential for nonlinear actuators.

B-site modified Bi 3.25 La 0.75 Ti 3- x Ta x O 12 ceramics were prepared by the conventional solid-state reaction method. The influence of Ta 2 O 5 on microstructure and electric properties of the ceramics was investigated. The results demonstrated that Ta 5+ ions were dissolved into the perovskite lattice and homogeneously distributed in the matrix without forming any minority phase. The conduction mechanism and dielectric response behavior were transformed with Ta substation, which is triggered by varied structural distortion characteristics and defect diploes. The Curie temperature decreased gradually with increasing Ta content and a relaxor-like behavior was observed for x = 0.09 sample. The internal bias field is decreased with Ta doping, because the substitution of Ta 5+ at B-site contributes to release the involved oxygen vacancies in defect diploes. Moreover, further increasing Ta content causes a reduction in the oxygen vacancies located at lattice misfits, resulting in a decrease of coercive fields. An improved ferroelectric properties were obtained for x = 0.09 sample with a relatively lower coercive field and a larger spontaneous polarization.

The ZnO-Bi2O3-MnO2-xSiO2 (ZBMS) varistor was prepared at a low sintering temperature of 880 °C via the conventional solid state method. The phase transformation, microstructure, and electrical properties of the ZBMS varistor were studied as a function of doping amount of SiO2. It is showed that the growth of ZnO grain is restrained by the introducing of SiO2; and the grain size decreases from 4.68 μm to 2.98 μm. The breakdown voltage E1mA exhibits a simultaneous variation from 608.11 V/mm to 1232.88 V/mm. It is also revealed that SiO2 has a significant effect on the Schottky barrier structure. As a result, the highest barrier height φb of 5.34 eV is attained at a composition of x = 2.0 wt%, which contributes to the highest nonlinear coefficient α of 73.68. Moreover, all the samples show low leakage current of IL

0.755Bi0.5Na0.5TiO3–0.065BaTiO3–0.18SrTiO3 (BNT–BT–ST) thin films with various thicknesses were grown by sol-gel process. The effects of thickness on structure and electric properties of the films ...

The Aurivillius phase SrBi4Ti4O15 (SBT) powders were synthesized by a hydrothermal reaction with 20% acetic acid solution as solvent at 200°C for 24 h, then the piezoelectric ceramic was prepared u...

Lead-free luminescent multifunctional (Ba0.99Ca0.01)1−xEux(Ti0.98Zr0.02)O3 (x = 0, 0.002, 0.004 and 0.006) (BCEZT-x) ceramics were successfully synthesized using solid state reaction method. The effects of Eu addition on the phase structure and electrical properties of the BCEZT-x ceramics were systematically studied. Results show that orthorhombic–tetragonal (O–T) phase transitions temperature decreases with increasing Eu content, and coexistence of the O and T phases is observed near room temperature (RT) in the composition range of 0.002–0.004. All the BCEZT-x ceramics exhibit high Curie temperature (T C > 115 °C), especially T C ≈120 °C for the composition of x = 0.002. The BCEZT-x ceramics at x = 0.002 exhibit excellent piezoelectric properties (d 33 = 400 pC/N and k p = 52%), due to the coexistence of the O and T phase at RT. Meanwhile, a large strain S max of ~0.22% is obtained at x = 0.004 for the BCEZT-x ceramics. Moreover, studies on photoluminescence properties of the ceramics shows that luminescence properties are strongly dependent on the doping concentration for the BCEZT-x ceramics. The strongest photoluminescence occurs at x = 0.004 of the BCEZT-x ceramics. Upon the excitation of 465 nm light, all the BCEZT-x ceramics have two intense emission peaks around 593 nm and 616 nm. According to the CIE chromaticity diagram, the ceramics possess a bright yellow light (x = 0.483, y = 0.4991). These results indicate that the BCEZT-x ceramics have significant technological potential as multifunctional devices due to their excellent electric and luminescence properties.

Multifunctional ferroelectric ceramics SrBi4−x Sm x Ti4O15 (SBT–xSm) with reddish orange-emitting and good piezoelectric properties were designed and fabricated using a conventional fabrication process. Results show that samples exhibited strong reddish-orange emissions and their PL spectrum exhibiting a strong red emission at 603 nm attributed to the characteristic f–f transition 4G5/2→6H7/2 under visible blue light excitation. The intensity of emission was strongly dependent on the doping concentration. What is more, it was also found that Sm3+ doping significantly enhanced the electrical properties. At x = 0.006, samples exhibit the optimal ferroelectric (2P r = 22.23 μC/cm2) and piezoelectric (d 33 = 19 pC/N) properties, together with excellent piezoelectric temperature stability. These results reveal that SBT–xSm ceramics may have promising applications in future optical temperature sensors.

Multifunctional ferroelectric ceramics (Bi 0.5 Na 0.5 ) 0.945 Ba 0.065 Ti 1− x (Er 0.5 Sb 0.5 ) x O 3 (BNBT6.5–100 x ES) with bright upconversion emission and field-induced large strain were prepared through conventional solid state sintering method. Results showed that Er/Sb-codoping into BNBT6.5 induced a phase transition from ferroelectric to ergodic relaxor phase. Near the phase boundary ( x = 0.50%), a large fatigue-resistant strain of 0.40% at a driving field of 80 kV/cm was obtained. Besides the excellent strain properties, Er/Sb-codoped BNBT6.5 samples exhibited a strong photoluminescence with a bright green emission at 526 nm and 549 nm assigned to ( 2 H 11/2 , 4 S 3/2 ) → 4 I 15/2 transitions and a relatively weak red emission located at 663 nm assigned to 4 F 9/2 → 4 I 15/2 transition under the 980 nm excitation. As a multifunctional material, it has potential application as a multifunctional device such as “on-off” actuator, optical-electro integration and coupling device applications.

A red-emitting piezoelectric ceramic of SrBi4−xEuxTi4O15 (SBT-xEu, x = 0.000–0.010) with strong photoluminescence and improved piezoelectric properties was prepared. All samples had a bismuth oxide layered structure with a dense microstructure. After Eu3+ doping, a bright red photoluminescence upon blue light excitation of the 400 nm to 500 nm was observed in the modified samples. Upon the excitation of 465 nm light, the emission peaks centered at 537–703 nm were noted, which correspond to a weak green 5D1 → 7F1 transition and the characteristic emission bands (5D0 → 7FJ, J = 1–4). Simultaneously, Eu3+ doping promotes electrical properties. At 0.6 mol.% Eu, samples exhibit the optimal electric properties (d33 = 22 pC/N, 2Pr = 19.86 μC/cm2 and Tc = 534°C), together with excellent temperature stability (25–450°C). As a multifunctional material, Eu-doped SBT ferroelectric oxide showed great potential in sensors and optical-electro integration device applications.

Rare-earth elements Dy3+, Er3+, Eu3+ and Pr3+-doped (K0.5Na0.5)NbO3 ceramics were prepared by traditional solid-state sintering method. The structure, piezoelectric, ferroelectric and photoluminescence properties of the samples were investigated. All ceramics possessed orthorhombic perovsktie structures at room temperature without impurity phases. The ceramics were well sintered and displayed considerably dense microstructure and inhomogeneous grain size distributions. Good ferroelectricity could be realized in the proposed compositions. All KNN-RE ceramics exhibited photoluminescence effects. The KNN-Pr sample showed little degradation in both switchable polarization and the converse piezoelectric coefficients d 33* after 105 switching cycles, meanwhile, it had the highest photoluminescence intensity. The work provides an alternative routine to develop new multifunctional materials.

An electric-field-induced large strain and strong photoluminescence was achieved by introducing trivalent Pr 3+ as the activator into 0.92(Bi 0.5 Na 0.5 )TiO 3 − 0.08(Ba 0.90 Ca 0.10 )(Ti 0.92 Sn 0.08 )O 3 (BNT−8BCST) ceramics. Around a critical composition of 0.4 mol% Pr 3+ , a large strain of ∼0.39% with a relatively small hysteresis compared with existing lead-free Bi-perovskite ceramics was obtained. In particular, the strain is very resistant to field cycling and thermal shock, giving the materials attractive for its exceptionally good fatigue resistance and high temperature stability. Besides the excellent electrical properties, Pr 3+ -modified BNT−8BCST host exhibits a strong photoluminescence with a bright red emission at 610 nm assigned to 1 D 2 → 3 H 4 transitions of the Pr 3+ ions upon a blue light excitation of 400–500 nm. The photoluminescence can be enhanced through poling treatment of the samples. Moreover, samples have a superior water resistance property which almost maintaining the same photoluminescence intensity after 40 h water immersion time. These results suggest the material may have potential application as a multifunctional device such as “on-off” actuator and electric field-controlled photoluminescence devices by integrating its excellent luminescence and electrical properties.

In this paper, the effect of rare earth oxide nano-additives on micro-mechanical properties and erosion behavior of Fe-Cr-C-B hardfacing alloys was studied. Optical microscope was used to observe microstructure of hardfacing alloys. X-ray diffractometer was used to analyze phases of hardfacing alloys. Vickers micro-hardness tester was used to measure micro-hardness of constitutional phases. Fracture toughness (K IC ) of primary carbide was calculated by indentation method. Erosion tests were carried out using JZB sand blaster. The experimental results showed that hardfacing alloys were hypereutectic, which were composed of M 7 C 3 , martensite and retained austenite. Nano-additives increased the hardness and the K IC of primary carbide. The hardness of the primary carbide in the hardfacing alloy with 0.288 wt% nano-additives reached a maximum of 1716.54HV 0.2 . The K IC of the primary carbide in the hardfacing alloy with 0.432 wt% nano-additives was 9.27 MPa√m, which increased by 51.7% than that of the primary carbide in the hardfacing alloy without nano-additives. Erosion test results showed that nano-additives improved the erosion resistance of hardfacing alloys. The erosion rate of the hardfacing alloy with 0.432 wt% nano-additives decreased by 31.8% than that of the hardfacing alloy without nano-additives.

Novel green-emitting piezoelectric ceramics of SrBi4−x Er x Ti4O15 (SBT-xEr) were prepared. Strong up-conversion with bright green (524 and 548 nm) and a relatively weak red (660 nm) emission bands were obtained under 980 nm excitation at room temperature, which is attributed to the intra 4f–4f electronic transition of (2H11/2, 4S3/2)–4I15/2 and the transition from 4F9/2 to 4I15/2 of Er3+ ions, respectively. Simultaneously, Er3+ doping promotes the electrical properties. At 0.8 mol%Er, the optimal electric properties with high Curie temperature of T c ~527 °C, large remanent polarization of 2P r ~14.92 μC/cm2 and piezoelectric constant of d 33 ~17 pC/N was achieved. As a multifunctional material, Er3+ doped SBT showed a great potential to be used in 3D-display, bio-imaging, solid state laser and optical temperature sensor.

ZnO–Bi2O3–TiO2–Co2O3–MnO2-based (ZBTCM) varistors were fabricated via the conventional solid-state method, and the effect of SiO2 content on the phase transformation, microstructure, and electrical properties of the ZBTCM had been investigated. Results showed that this varistor can be sintered at a low temperature of 880°C with a high sintering density above 0.95 of the ZnO theoretical density. In these components, SiO2 acts as a controller in ZnO grain growth, decreasing the grain size of ZnO from 3.67 to 1.92 μm, which in turn results in an increase in breakdown voltage E1mA from 358.11 to 1080 V/mm. On the other hand, SiO2 has a significant influence on the defect structure and component distribution at grain-boundary regions. When SiO2 content increases from 0 to 4 wt%, the value of the interface state density (Ns) increases sharply. At the same time, the electrical properties are improved gradually, and reach an optimized value with the nonlinear coefficient (α) up to 54.18, the barrier height (ϕb) up to 2.90 eV, and the leakage current (IL) down to 0.193 μA/cm2.

Lead-free piezoelectric ceramics (Bi0.5Na0.5)0.935Ba0.065Ti1-x(Al0.5Sb0.5)xO3 (BNBT6.5–xAS) were prepared by a conventional solid sintering technique and their structure and electrical properties were systematically investigated. With increasing AS content, BNBT6.5-xAS ceramics underwent a phase transition from ferroelectric to relaxor phase, accompanied with the significant disruption of ferroelectric order. Accordingly, the ferroelectric–relaxor transition temperature TF-R was shifted down to room temperature, and thus a large unipolar strain of 0.46% (at 80 kV/cm) corresponding to a large signal d33*of 573 pm/V is obtained in 1.5 mol% AS-modified samples.

(Ba 0.99 Ca 0.01 )(Ti 0.98 Zr 0.02 )O 3 (BCZT) and Pr-doped samples (Pr 0.002 Ba 0.988 Ca 0.01 )(Ti 0.98 Zr 0.02 )O 3 (BCZT-A) as well as 0.998(Ba 0.99 Ca 0.01 )(Ti 0.98 Zr 0.02 )O 3 -0.002PrO 1.5 (BCZT-W) lead-free piezoelectric ceramics were prepared by conventional solid state reaction method. The structural, dielectric, piezoelectric, ferroelectric and luminescence properties of the Pr-doped BCZT ceramics were systematically studied. The orthorhombic-tetragonal (O–T) phase transition temperature decreased obviously, while Curie temperature ( T C ) maintained at 118 °C for both of the Pr-doped BCZT ceramics. The BCZT-A ceramics exhibited the best piezoelectric properties ( d 33 = 344 pC/N) and ferroelectric properties ( P r = 13.042 μC/cm 2 ). Meanwhile, desired luminescence properties (bright reddish-orange light, emission peak centered at 649 nm) were obtained under an excitation of 448 nm at room temperature for BCZT-A and BCZT-W ceramics. The luminescence properties of the BCZT-A ceramics were better than those of the BCZT-W ceramics. Asymmetric structure, coexistence of orthorhombic and tetragonal phases at room temperature and less oxygen vacancies exhibited in BCZT-A ceramics could result in the improved piezoelectric properties and luminescence properties simultaneously. These results suggest that the BCZT-A ceramics have potential application as a multifunctional device by integrating its excellent electrical and luminescence properties.

The effects of M 2 O 5 (M = Nb, Ta, Sb) addition on the phase transition and electrical properties of 0.94Bi 0.5 Na 0.5 TiO 3 –0.06BaTiO 3 (BNBT6) lead-free ceramics were studied. Results showed that M substitution into BNBT6 induced a phase transition from coexistence of ferroelectric tetragonal and rhombohedral to a relaxor pseudocubic with a significant disruption of the long-range ferroelectric order. Accordingly, large strain response of 0.42–0.43% with fatigue-free behavior, which is due to a reversible field-induced ergodic relaxor-to-ferroelectric phase transformation, was obtained at 0.5 mol% M content. Furthermore, as the compositions ( x ≥ 0.06) lied deep in the pseudocubic region of the phase diagram, a high, purely electrostrictive effect with large electrostrictive coefficient Q 33 of 0.020–0.024 m 4 /C 2 was achieved. More interestingly, the obtained BNBT6-based electrostrictors showed good resistance to both long-term electric cycling (up to 10 6 cycles) and thermal influence (20–160 °C), rendering them suitable for high-precision positioning devices and other actuators.

High chromium cast iron (HCCI) hardfacing alloys with nano-additives were prepared. The effects of nano-additives on the microstructure of hardfacing alloys were studied by a scanning electron microscope (SEM) and an X-ray diffractometer (XRD). A Rockwell hardness tester was used to measure the hardness represented by Rockwell C-scale hardness (HRC). The friction and wear behavior of the hardfacing alloys with different nano-additives was investigated using ball-on-disc sliding wear tests. The experimental results showed that the volume fraction of primary carbide increased and then decreased with the increase of nano-additives. The volume fraction of primary carbide in the hardfacing alloy with 0.288 wt% nano-additives increased by 27% than that of the hardfacing alloy without nano-additives. The XRD results showed that hardfacing alloys were composed of M7C3 (M mainly represented Fe and Cr), martensite and retained austenite. The hardness of the hardfacing alloy without nano-additives was 61.5HRC. The hardness of the hardfacing alloy with 0.288 wt% nano-additives reached 64.5HRC. The wear rate of the hardfacing alloy with 0.288 wt% nano-additives decreased by 21.2% than that of the hardfacing alloy without nano-additives. The main wear mechanism of the hardfacing alloys with nano-additives was abrasion wear accompanied by severe adhesion wear.

The electrical properties of ZnO-Bi 2 O 3 -MnO 2 -SiO 2 –based (ZBMS) varistors as a function of synthetic multi-phase (SMP) produced by pre-sintering the mixture of 16Bi 2 O 3 ·Co 2 O 3 (Bi-Co-O) were investigated. The Bi-Co-O SMP can modify the transportation of the absorbed oxygen in grain boundary layers and then improves electrical properties. Samples doped with 8 wt% SMP shows the excellent electrical properties: the nonlinear coefficient α increased up to 45.97 corresponding to the high barrier height φ b of 1.23 eV, the leakage current J L decreased to 0.5 μA.