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The phase relations of the R2Fe14B–Ce2Fe14B (R= Nd, Pr) pseudobinary systems have been investigated by using X-ray powder diffraction, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and differential thermal analysis. The X-ray powder diffraction results show that continuous solid solutions were formed in this R2Fe14B–Ce2Fe14B (R= Nd, Pr) pseudobinary systems, and all (R,Ce)2Fe14B solid solutions belong to the tetragonal structure with space group P42/mnm. With the increase in Ce content, the lattice parameters a, c, the peritectic reaction temperatures of the (R, Ce)2Fe14B (R= Nd, Pr) solid solutions decrease linearly, and the cell volume Vvaries in the form of the regression line. Based on the X-ray powder diffraction results and differential thermal analysis data, the quasi-binary phase diagrams of the R2Fe14B–Ce2Fe14B (R= Nd, Pr) systems have been established.

ABSTRACTThe stability of the phase Pr3Pt4in a series of Pr42.9Pt57.1-xFex(x = 0, 1, 2, 3) alloys was investigated by using X-ray diffraction (XRD) and differential thermal analysis (DTA). It was found that the phase Pr3Pt4(3:4 phase) with Pu3Pd4-type structure formed in the Pr42.9Pt57.1-xFexalloy for x = 0 annealed at 1173 K for two weeks. However, the fraction of the 3:4 phase decreased rapidly with increasing x, and approached zero when x = 3. XRD and DTA results showed that the 3:4 phase decomposes gradually into the two neighboring phases PrPt (1:1 phase) and (Pr, Fe)Pt2(1:2 phase), and the decomposition temperature of the reaction 3:4 → 1:1 + 1:2 is shifted slightly to higher temperature with increasing x. The reason for this phase decomposition is briefly discussed by the preferential site occupation of Fe in Pr3Pt4.

Morphotropic phase boundary (MPB) plays a key role in tuning piezoelectric responses of ferroelectric ceramics. Here, Bi0·5Na0·5TiO3modified BiFeO3BaTiO3ternary solid solutions of 0.7BiFeO3-(0.3-x)BaTiO3-xBi0.5Na0·5TiO3(referred to as BF-BT-xBNT, 0.00 ≤ x ≤ 0.04) were prepared for lead-free piezoelectrics. All the ceramics exhibit an MPB with coexisting rhombohedral (R) and tetragonal (T) phases, and the R/T phase ratio decreases upon increasing x. The increment of BNT promotes the grain growth, lowers the leakage current and Curie temperature (TC), and gradually drives the ferroelectric to relaxor transition. Because of the MPB with appropriate R/T phase ratio, increased grain size and density, and decreased leakage current, the well-balanced performance between d33 = 206 pC/N and TC = 488 °C is obtained in x = 0.01 case. In addition, the further enhanced in-situ d33 = 286–347 pC/N is obtained in BF-BT-xBNT ceramics along with the improved depolarization temperature Tdfrom 280 to 312 °C, showing a potential application for lead-free piezoceramics at high temperature.

A high-temperature accelerometer plays an important role for ensuring normal operation of equipment in aerospace, such as monitoring and identifying abnormal vibrations of aircraft engines. Phase transitions of piezoelectric crystals, mechanical failure and current leakage of piezoresistive/capacitive materials are the prominent inherent limitations of present high-temperature accelerometers working continuously above 973 K. With the rapid development of aerospace, it is a great challenge to develop a new type of vibration sensor to meet the crucial demands at high temperature. Here we report a high-temperature accelerometer working with a contact resistance mechanism. Based on the improved graphene aerogel (GA) prepared by a modulated treatment process, the accelerometer can operate continuously and stably at 1073 K and intermittently at 1273 K. The developed sensor is lightweight (sensitive element <5 mg) and has high sensitivity (an order of magnitude higher than MEMS accelerometers) and wide frequency response range (up to 5 kHz at 1073 K) with marked stability, repeatability and low nonlinearity error (<1%). These merits are attributed to the excellent and stable mechanical properties of the improved GA in the range of 299–1073 K. The accelerometer could be a promising candidate for high-temperature vibration sensing in space stations, planetary rovers and others.

An imminent challenge of lead-free Bi0.5Na0.5TiO3-based (BNT) piezoceramics is that the giant piezoelectric constant (d33) caused by the morphotropic phase boundary is incompatible with a high depolarization temperature (Td) and ultralow temperature coefficient (Ttc) of the real-time d33, which severely hinders their industrial application in the field of elevated temperatures. Herein, a sandwich-structured 0.94Bi0.5Na0.5TiO3–0.06BaTiO3/0.89Bi0.5Na0.5TiO3–0.11BaTiO3/0.94Bi0.5Na0.5TiO3–0.06BaTiO3(SWS-6/11/6BT-y, where yrefers to the weight fraction of the BNT-11BT solid solution) ceramic composite is engineered for mitigating the conflict between d33, Tdand Ttc. Following this strategy, ultrahigh Tdnear the Curie point (225 °C, close to that of the BNT-11BT layer) and relatively large d33(130 pC/N, close to that of the BNT-6BT layer) are simultaneously realized in a SWS-6/11/6BT-40%-Q ceramic composite. More importantly, the ultralow Ttc(0.07%) of real-time d33is also achieved in this work. The structural heterogeneity yields the high piezoresponse, and the built-in field resulting from layer-type ceramic composites provides the driving force to promote the diffused ferroelectric–relaxor phase transition and the resultant ferroelectric order with high Td. The above synergistic contributions realize the remission of the d33–Td–Ttcconflict in a sandwich-structural SWS-6/11/6BT-40% ceramic composite. Thus, our work provided a path for designing the BNT-based piezoceramics with potential for industrial applications.

In order to develop novel materials based on rare earth (RE) boride and/or transition metals, phase equilibria and thermodynamic information of the RE–B based alloys are indispensable. On the basis of experimental phase equilibria and thermodynamic properties, thermodynamic assessments of the RE–B (RE= La, Sm, Gd and Tb) binary systems were carried out by the CALPHAD (Calculation of Phase Diagram) method. Self-consistent parameters of the RE–B (RE= La, Sm, Gd and Tb) binary systems were obtained, which can be used to reproduce well the experimental data. Furthermore, in combination with the previous assessments of the RE–B binary systems in the literature, phase equilibria and thermodynamic properties of the RE–B (RE= La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm and Lu) binary systems are discussed systematically. The tendency of phase equilibria and thermodynamic information as a function of REatomic number is demonstrated. In general, the enthalpy of mixing of liquid RE–B alloys and the enthalpy of formation of the RE–B intermetallic compounds become more and more negative with the increase in REatomic number (except for La, Ce, Pr and Nd), while the phase transition temperatures for the RE–B intermetallic compounds increase gradually.

New energy vehicles and offshore wind power industries have a high demand for sintered Nd–Fe–B magnets with high intrinsic coercivity and high corrosion resistance. In this study, the magnetic properties, anticorrosion properties, and microstructure of Nd–Fe–B sintered magnets with the intergranular addition of low-melting-point eutectic Tb68Ni32alloy powders were investigated. The aim is to determine if the addition of Tb68Ni32can improve these properties. A low melting-point eutectic alloy Tb68Ni32powders was prepared as a grain boundary additive and blended with the master alloy powders prior to sintering. The coercivity of the resultant magnets gradually increases from 1468 to 2151 kA/m by adding increasing amounts of Tb68Ni32. At the same time, the remanence first increases and then slightly decreases. After studying the microstructure and elemental composition of the Tb68Ni32added magnets, it is found that the significant increase in coercivity and the negligible reduction in remanence is due to densification, improved grain orientation, a uniform and continuous boundary phase distribution, as well as the generation of a (Nd,Pr,Tb)2Fe14B “core–shell” structure surrounding the main-phase grain. Moreover, the corrosion resistance of the magnet is greatly improved owing to the enhancement of electrochemical stability, as well as the optimization of the distribution and morphology of the intergranular phase.

The table-like magnetocaloric effect is significant for the magnetic refrigeration applications above 20 K based on the Ericsson cycle. Herein, we prepared a series of Nd6Fe13Pd1–xCux(x = 0.05, 0.1, 0.15) compounds by the arc-melting method. These compounds show the single crystalline phase in the tetragonal Nd6Fe13Si-type structure with the space group I4/mcm. A magnetic phase transition from ferromagnetism to antiferromagnetism and a metamagnetic transition from the antiferromagnetic state to the ferromagnetic state are observed in each of the compounds. The compounds exhibit table-like magnetocaloric effects with large refrigerant capacities. A constant ΔSMin a temperature span of 40 K in the Nd6Fe13Pd0.85Cu0.15compound are observed. For a field change of 0–5 T, the peak values of –ΔSMfor the Nd6Fe13Pd0.95Cu0.05, Nd6Fe13Pd0.90Cu0.10, and Nd6Fe13Pd0.85Cu0.15compounds are estimated to be 4.8, 4.6 and 4.4 J/(kg·K) with corresponding refrigerant capacity values of 323, 331 and 316 J/kg, respectively. The obtained table-like magnetocaloric effects with large refrigerant capacities as well as fairly small thermal and magnetic hysteresis deem these series of compounds good candidates for single-phase magnetic refrigeration based on the Ericsson cycle.

In various ferroelectric-based photovoltaic materials after low-band-gap engineering, the process by which high-field polarization induces the depolarizing electric field (Edp) to accelerate the electron–hole pair separation in the visible light photocatalytic process is still a great challenge. Herein, a series of semiconducting KN-based ferroelectric catalytic materials with narrow multi-band gaps and high-field polarization capabilities are obtained through the Ba, Ni, and Bi co-doping strategy. Stable Edpcaused by high-field poling enhanced the visible photocatalytic hydrogen evolution in a 0.99KN–0.01BNB sample with a narrow band gap and optimal ferroelectricity, which can be 5.4 times higher than that of the unpoled sample. The enhanced photocatalytic hydrogen evolution rate can be attributed to the synergistic effect of the significant reduction of the band gap and the high-field-polarization-induced Edp. The change in the band position in the poled sample further reveals that high-field poling may accelerate the migration of carriers through band bending. Insights into the mechanism by which catalytic activity is enhanced through high-field-polarization-induced Edpmay pave the way for further development of ferroelectric-based catalytic materials in the photocatalytic field.

Realizing the high piezoelectric coefficient d33across a broad operating temperature range from subzero to high temperature in BNT-based piezoceramics is confronted with a severe challenge because of the restriction of the d33-Tdtrade-off, which undoubtedly hinders the practical application of cryogenic and normal electromechanical devices. Herein, a synergistic strategy of integrating the quenching process, interface-diffused sintering and bilayer structure design is proposed to mitigate the d33-Tdconflict. By this strategy, the 0.93Bi0.5Na0.5TiO3-0.07BaTiO3(BNT-7BT)/0.89Bi0.5Na0.5TiO3-0.11BaTiO3(BNT-11BT)-D + Q ceramic composites (the letters D and Q refer to the interface-diffused sintering and quenching process, respectively) not only possess the relatively large piezoelectric coefficient d33(135 pC/N, 25 °C) and high depolarization temperature Td(210 °C) but also exhibit an ultrahigh operating temperature range from −75 °C to 210 °C, which is much higher than that of BNT-7BT (−75°C-93 °C) and BNT-11BT (−20°C-206 °C) ceramics. The relatively large d33derives from the coexistence of rhombohedral R3cphase and tetragonal P4bmand P4mmphases, thereby maintains the decent piezoelectric response at subzero temperature. The high Tdis connected with the high P4mmphase ratio, the large built-in field Eband diffused ferroelectric-relaxor phase transition. Therefore, this work provides a new path for designing the BNT-based composite materials with a broad operating temperature region.

In this paper, polycrystalline samples of Bi1–xSmxFeO3(x = 0, 0.05, 0.1, 0.15) were successfully synthesized by sol-gel method. The effects of Sm concentration on the crystal structure, morphology, chemical states, magnetic properties and microwave absorption performance were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), a vibrating sample magnetometer (VSM) and a Vector network analyzer (VNA), respectively. The results show that the rare earth Sm doping causes the crystal structure to change. When x ≤ 0.1, Bi1–xSmxFeO3is the distorted rhombohedral structure with space group R3c. With the increase of Sm doping amount to x = 0.15, the phase structure of Bi1–xSmxFeO3changes from rhombohedral structure to cubic structure with the space group Pm3¯m. The particle size decreases with the increase of the Sm doping amount. The analysis results show that Sm doping can effectively reduce the oxygen vacancies and significantly improve its magnetic properties. The results exhibit that moderately doped rare earth Sm element can effectively improve microwave absorption properties of Bi1–xSmxFeO3powders. When Sm doping amount of x is 0.1, the Bi0.9Sm0.1FeO3compound has good microwave absorption performance, and the minimum reflection loss value of Bi0.9Sm0.1FeO3powder reaches about −32.9 dB at 11.7 GHz, and its effective absorption bandwidth (RL < −10 dB) is 2.6 GHz with the optimal matching thickness of 2.0 mm.

Zero-dimensional lead-free organic–inorganic hybrid metal halides have drawn attention as a result of their local metal ion confinement structure and photoelectric properties. Herein, a lead-free compound of (Gua)3Cu2I5(Gua = guanidine) with a different metal ion confinement has been discovered, which possesses a unique [Cu2I5]3–face-sharing tetrahedral dimer structure. First-principles calculation demonstrates the inherent nature of a direct band gap for (Gua)3Cu2I5, and its band gap of ∼2.98 eV was determined by experiments. Worthy of note is that (Gua)3Cu2I5exhibits a highly efficient cool-white emission peaking at 481 nm, a full-width at half-maximum of 125 nm, a large Stokes shift, and a photoluminescence quantum efficiency of 96%, originating from self-trapped exciton emission. More importantly, (Gua)3Cu2I5single crystals have a reversible thermoinduced luminescence characteristic due to a structural transition scaled by the electron–phonon coupling coefficients, which can be converted back and forth between cool-white and yellow color emission by heating or cooling treatment within a short time. In brief, as-synthesized (Gua)3Cu2I5shows great potential for application both in single-component white solid-state lighting and sensitive temperature scaling.

Abstract: CuO-doped K0.5Na0.5NbO3(KNN)-based lead-free piezoelectric single crystals were realized by using a seed-free solid-state crystal growth (SFSSCG) method. The effect of the CuO addition on the single-crystal growth, microstructure and electrical properties of the systems was studied systemically. The addition of CuO is beneficial for the growth of the KNN-based crystals and decreases the width of ferroelectric domains of the crystals. In particular, the CuO doping significantly reduces the dielectric loss of the crystals. The lowest dielectric loss tanδof 1% was achieved for the CuO-doped crystals with high piezoelectric constant and Curie temperature. The study on the leakage behavior of the crystals shows that the main electrical conduction mechanism is the space-charge-limited-current (SCLC). A coexisting crystalline structure with orthorhombic and tetragonal phases forms in the (1 − x)[KNN-LiBiO3]-xCuO crystals at x= 0.007–0.009. The growth kinetics and mechanism of the crystals were also investigated. Graphic Abstract:

In this work, the (1−x)Bi0.5Na0.5TiO3-xBaNi0.5Nb0.5O3(BNT-BNN; 0.00 ⩽ x⩽ 0.20) ceramics were prepared via a high-temperature solid-state method. The crystalline structures, photovoltaic effect, and electrical properties of the ceramics were investigated. According to X-ray diffraction, the system shows a single perovskite structure. The samples show the normal ferroelectric loops. With the increase of BNN content, the remnant polarization (Pr) and coercive field (Ec) decrease gradually. The optical band gap of the samples narrows from 3.10 to 2.27 eV. The conductive species of grains and grain boundaries in the ceramics are ascribed to the double ionized oxygen vacancies. The open-circuit voltage (Voc) of ∼15.7 V and short-circuit current (Jsc) of ∼1450 nA/cm2are obtained in the 0.95BNT-0.05BNN ceramic under 1 sun illumination (AM1.5G, 100 mW/cm2). A larger Vocof 23 V and a higher Jscof 5500 nA/cm2are achieved at the poling field of 60 kV/cm under the same light conditions. The study shows this system has great application prospects in the photovoltaic field.

The phase relations in the Ce2Co17-Sm2Co17system over the whole concentration range have been studied by means of Xray powder diffraction, differential thermal analysis and scanning electron microscopy equipped with energy dispersive Xray spectroscopy. The X-ray powder diffraction results reveal that all the alloys (Ce1-xSmx)2Co17are similar to the end member of the investigated system, Sm2Co17. It is implied that continuous solid solutions are formed in this system. The lattice parameters and unit cell volumes of (Ce1-xSmx)2Co17solid solutions increase linearly with x increasing from 0 to 1.0. The occurrence of the polymorphic transformation reaction α-(Ce, Sm)2Co17= β-(Ce, Sm)2Co17is confirmed in the Ce2Co17-Sm2Co17system, but its transition temperature cannot be determined. The differential thermal analysis measurements show that both the decomposition temperature and the Curie temperature of the (Ce1-xSmx)2Co17alloys increase gradually with increasing Sm content. Based on the X-ray powder diffraction results and differential thermal analysis data, the tentative vertical section of Ce2Co17-Sm2Co17pseudobinary system has been constructed.

Single crystalline h-MoO3nano- and microrods were successfully synthesized using modified liquid-phase processes with concentrated HNO3and H2SO4. Their X-ray powder diffraction (XRD) data were unambiguously indexed based on a hexagonal structure with the lattice constants a≈ 10.57 and c≈ 3.72 Å instead of a= 10.53 and c= 14.98 Å (JCPDS 21-0569) usually adopted. Rietveld refinements of the XRD data were pioneeringly performed based on the (Na·2H2O)Mo5.33[H4.5]0.67O18structure with the space group of P63/mregardless of H+and Na+. Nanorods synthesized under different conditions show different sizes and aspect ratios. Annealing at 300 °C for 3 h significantly improves the crystallinity and phase purity of as-synthesized h-MoO3rods, which is evidenced by sharpening of peaks in micro-Raman spectra with no shift. An irreversible transition from h-MoO3to α-MoO3occurring between 413 and 436 °C can be triggered by irradiation of either electrons or laser with high energies or powers as well. The turning points on both differential thermal analysis (DTA) and thermogravimetry (TG) curves show presence of water molecules interacted differently with the lattice which escape at different temperatures. h-MoO3rods reduce the temperatures of soot oxidation to 482−490 °C, much higher than its structural transition temperatures. This makes it simply suitable for catalyzing reactions taking place at temperatures lower than the transition temperatures, say, as the catalyst of the selective oxidation of methanol.

Thermodynamic optimization of the binary rare earth alloy (Ce–La, Ce–Pr, Ce–Nd and La–Nd) systems was performed in this work through the CALPHAD method based on the critical evaluation of all available phase diagram and thermodynamic data reported in the literature. During the thermodynamic modeling, the solution phases including liquid, bcc, fcc and dhcp, were treated as the substitutional solution model. Thermodynamic parameters of the stable phases in the Ce–La, Ce–Pr, Ce–Nd and La–Nd binary systems are obtained finally and would be used directly to develop the thermodynamic database of the multi-component Nd–Fe–B-based alloys, which is indispensable for designing alloy compositions and processes of Nd–Fe–B permanent magnets with highly abundant rare earth metals.

The effect of wheel speed on phase formation and magnetic properties of (Nd0.4La0.6)15Fe77.5B7.5and (Nd0.4La0.6)13.4Fe79.9B6.7ribbons prepared by melt-spinning method was investigated experimentally. Based on X-ray diffraction results, all melt-spun ribbons consist of the main phase with the tetragonal 2:14:1 type structure and the minor α-Fe phase. Magnetic measurements show the maximum magnetic energy product ((BH)max) and the remanence (Mr) increases firstly and then decreases with the increase of wheel speed, while the coercivity (Hci) increases, resulting from the variation of the average volume fraction of the α-Fe phase and the average grain size in the melt-spun ribbons. Using Henkel plots, the interaction between the 2:14:1 phase and the α-Fe phase in the melt-spun ribbons was analyzed and the intergranular exchange coupling is manifested. Optimal magnetic properties of Hci = 7.27 kOe, Mr = 90.94 emu/g and (BH)max = 12.10 MGOe are achieved in the (Nd0.4La0.6)15Fe77.5B7.5ribbon with the wheel speed of 26 m/s. It indicates that magnetic properties of Nd-Fe-B melt-spun ribbons with highly abundant rare earth element La can be improved by optimizing alloy composition and preparation process.

With the intention to explore excellent magnetocaloric materials, the intermetallic compound GdPd was synthesized by arc melting and heat treatment. The microstructure, magnetic and magnetocaloric properties of the intermetallic compound of GdPd were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and the physical property measurement system (PPMS). A large reversible magnetocaloric effect is observed in GdPd accompanied by a second order magnetic phase transition from paramagnetism to ferromagnetism at ∼39 K. The paramagnetic Curie temperature (θp) and the effective magnetic moment (μeff) are determined to be 34.7 K and 8.12 μB/Gd, respectively. The maximum entropy change (|ΔSMMax|)and the relative cooling power (RCP) under a field change of 5 T are estimated to be 20.14 J/(kg·K) and 433 J/kg, respectively. The giant reversible magnetocaloric effects (both the large ΔSMand the high RCP) together with the absence of thermal and field hysteresis make the GdPd compound an attractive candidate for low-temperature magnetic refrigeration.

The structural, magnetic and magnetocaloric properties of Gd7Pd3-xFexcompounds with x= 0, 0.2 and 0.4 were investigated. Rietveld refinement of X-ray powder diffraction shows that all the investigated samples are single phase and crystallize in a hexagonal structure with the space group P63mc. The lattice parameters (a, band c), and the cell volume (v) decrease with the increase of Fe content in Gd7Pd3-xFex, mainly because of the difference in atomic radius between Fe and Pd. Magnetization versus temperature in a magnetic applied field of 0.05 T shows that Gd7Pd3-xFexdisplays a paramagnetic (PM) – ferromagnetic (FM) transition with the Curie temperature TCdecreasing from 336 K for x= 0.0 to 319 K for x= 0.4. Under a field change of 0 to 5 T, the maximum values of the magnetic entropy change (|ΔSMmax|)$\left( {|{\rm{\Delta }}S_M^{max}|} \right)$are 5.09 J kg−1K−1, 4.89 J kg−1K−1, and 4.46 J kg−1for x= 0, 0.2, and 0.4, and the corresponding relative cooling powers (RCP) amount to 387.6 J Kg−1, 357.2 J · Kg−1, and 385.5 J Kg−1, respectively. The stable magnetocaloric effect and refrigeration capacity near room temperature reveal that the Gd7Pd3-xFexcompounds may be considered as refrigerants for magnetic refrigeration.

The effect of thermal and electrical histories on structure and dielectric behaviors is studied using 0.95(Bi0.5Na0.5)0.97(Li0.5Nd0.5)0.03TiO3-0.05BaTiO3(abbreviated as BNTLN0.03-BT5) ceramic as a selected system. Subtle structure change caused by annealing treatment, and pronounced phase transition and domain switching by electrical poling, are observed to occur, respectively. The dielectric constant and its strong frequency dispersion in unpoled samples decrease evidently by electrical poling due to electric field-induced ordered domain. The high temperature Maxwell-Wagner relaxor behavior vanishes by annealing treatment due to the loss of electrical inhomogeneity with interface charging effects. Piezoelectric properties are improved evidently by annealing treatment at 900 °C, implying a new appropriate method to improve piezoelectric properties.

The crystal structure and phase relations of the Pr2Fe14B-La2Fe14B system were investigated by X-ray powder diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The crystal structure parameters were determined by full-profile Rietveld refinements. The results revealed that all alloys of (Pr1–xLax)2Fe14B crystallized the Nd2Fe14B-type structure with the space group P42/mnmand formed a continuous solid solutions between x=0.0 and 1.0. The lattice parameter a, c, unit-cell volume Vand c/aratio increased linearly with the La concentration. Determined by thermogravimetry analysis, the Curie temperature (TC), phase transition temperature and melting temperature of (Pr1–xLax)2Fe14B decreased linearly upon the La content. Based on the results of DSC measurements and X-ray powder diffraction examinations, the phase diagram of the Pr2Fe14B-La2Fe14B system was built up.

The nano-crystalline La0.1Bi0.9FeO3compound was successfully synthesized by starch-based combustion method. The crystal structure and magnetic behavior were studied by temperature-dependent X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and magnetic measurements. The La0.1Bi0.9FeO3compounds crystallized in a rhombohedrally distorted perovskite structure with space group R3c. The substitution of La for Bi reduced the rhombohedral distortion. The structural phase transitions in La0.1Bi0.9FeO3driven by temperature showed that the extraordinary two-phase coexistence state of BiFeO3and LaFeO3was observed in a narrow temperature range of 630–700 °C. The magnetization of the La0.1Bi0.9FeO3sample was improved by heat treatment in the temperature range. When the heat treatment temperatures rose from 25 to 600 °C, the remanence (Mr) and coercivity (Hc) of the La0.1Bi0.9FeO3compound almost remained the same, and increased rapidly to 0.134 emu/g and 7.1 KOe on further increasing the heat treatment temperature to 650 °C.

The 0.93(Na0.5Bi0.5)1–xSmxTiO3-0.07BaTiO3multifunctional ceramics were prepared by solid-phase reaction method. The phase structure, microstructure, electrical and photoluminescent properties were systematically studied. With increasing x, the ceramics undergoes the phase transition from rhombohedral to tetragonal with some rhombohedral distortion, along with a reduced grain size and increased relative density. On the other hand, the Sm3+doping enhances the electric-field driven reversible phase transition and domain size, and reduces the domain walls, thereby contributing to improved piezoelectricity and decreased depolarization temperature (Td) from 91 °C to 40 °C. Excellent piezoelectric properties of d33 = 213 pC/N and kp = 29.9 % are achieved in the x = 0.010 ceramic. Under excitation (407 nm), the Sm3+-doped ceramic exhibits bright reddish-orange fluorescence at 564, 599, 646 nm and 710 nm. A polarization-induced enhancement of photoluminescence is obtained in BNBT-xSm ceramics with an improved relative intensity of emission band at 646 nm. These results indicate that Sm3+-doped BNBT ceramics show great potential in electro-optic integration and coupling device applications.

The polycrystalline samples PrNi5–xCox(x=0.0, 0.1, 0.2, 0.3, 0.4) were synthesized by arc smelting and high energy ball milling method. The phase structure, morphology, saturation magnetization and electromagnetic parameters of the alloy powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) and vector network analyzer (VNA), respectively. The results revealed that the lattice parameter aand cand unit-cell volume Vincreased with the increasing amount of Co substitution. The saturation magnetization increased as Co content increased. The minimum absorption peak frequency shifted towards lower frequency region with the increasing amount of Co substitution. And the minimum reflection loss of the PrNi5–xCoxpowders increased first and then decreased with the increasing amount of Co substitution. The PrNi5–xCoxalloys possessed the excellent microwave absorbing properties. The minimum reflection loss of the PrNi4.9Co0.1alloy all could reach −20.0 dB with the coating thickness ranging from 1.8 to 3 mm. The minimum reflection loss of PrNi4.9Co0.1powders was −36.20 dB at 7.76 GHz, and the frequency bandwidth of R<–10 dB reached about 1.50 GHz with the best matching condition d=2.0 mm.

The effect of rapid solidification on structure and electrochemical performance of the LaNi4.5Co0.25Al0.25hydrogen storage alloy was investigated by X-ray powder diffraction and a simulated battery test, including maximum capacity, cycling stability, self-discharge, and high-rate discharge ability (HRD). All the melt-spun alloys were single-phase with the CaCu5-type structure (space group P6/mmm). In comparison to the as-cast alloy, the rapidly quenched alloys manifested an improved homogeneity of composition and expanded lattice parameters. The electrochemical measurements showed that the activation property, cycling stability and self-discharge of the alloy electrodes were also improved for the rapid solidified alloys. The HRD of the as-cast alloy was better than those of all the rapidly solidified alloys. As the quenching rate increased, the HRD and exchange current density first decreased and then increased.

In the present study, we report a facile hydrothermal route developed to synthesize various 1D tellurium nanostructures including nanotubes, nanowires, and nanorods on a large scale. Te nanotubes with a tunable diameter from 200 nm to 2 μm are fabricated in NaOH solution. With poly(vinyl pyrrolidone) as the surfactant, ultrathin Te nanowires with a diameter of 5−8 nm are synthesized in NaOH solution. However, in both cases, only Te nanorods are obtained if NaOH is not added. The formation of Te nanotubes is attributed to the depletion of Te atoms at the surface of seeds. The influence of the reaction conditions including pH value, reaction temperature, reducing agent, and reactant concentration on the size and morphology of the Te nanostructures is investigated and the structural evolution with different growth rate is illustrated. A reduction reaction rate controlled growth mechanism has been proposed for the variable nanostructures. In addition, the obtained Te nanostructures are ideal templates to synthesize other Te-related nanocompounds, which is demonstrated by the synthesis of ultrathin Ag2Te nanowires through the direct reaction of ultrathin Te nanowires with AgNO3at room temperature.

Phase equilibria in the ternary NdCsSi system up to a Co:Nd atomic ratio of 2:1 and an Si:Nd atomic ratio of 3:5 were studied by means of X-ray powder diffraction. A total of seven ternary compounds were identified. Among the seven ternary compounds found in this system, the solid solubility of two compounds had not been reported previously: NdCo13, Si4with 2.5 ⩽x⩽ 4 and NdCo11, Si4with 1.2 ⩽x⩽ 1.8. Other new information includes the crystal structure of NdCo13, Si4. It has a tetragonal structure, related to the NaZn13-type, witha= 7.811−7.763Å, c= 11.430−11.464Å, and the atomic ordering is similar to Ce2Ni17Si4. A limited solid solution range has also been found for Nd2Co17, Si4. This isothermal section consists of 26 three-phase and four two-phase regions.

The crystal structure and thermal decomposition process of barium borophosphate BaBPO5have been studied by a combination of X-ray powder diffraction (XRD) and vibration spectroscopic techniques. The structure of BaBPO5is refined by Rietveld technique, which indicates that the structure units of this compound are PO4and BO4tetrahedra as well as irregular rare earth polyhedra. The thermal decomposition process of BaBPO5have been observed by the XRD patterns of decomposition samples under a series of heat treatments. The Raman and infrared spectra of the initial compound BaBPO5and its decomposed products Ba3BP3O12and Ba2P2O7showed the variations of the anion groups of boron and phosphorus. Assignments have been deduced from the systematic investigation of natural compounds and isotopic species with the help of isotopic shift data of10B–11B.

The crystal structures and magnetic properties of Mn and Cu-doped in La(T,Al)13 (T=Fe,Co) compounds have been investigated by means of X-ray powder diffraction and magnetic measurement. The results show that Mn doping stabilizes the cubic NaZn13 type structure, but both the magnetic moments and the Curie temperature decrease. Cu doping decreases the homogeneity region of the cubic NaZn13 type structure.

The crystal structure of the isomorphical rare earth borophosphate compounds,Ln7O6(BO3)(PO4)2(Ln=La, Nd, Gd and Dy), has been studied by a combination of X-ray powder diffraction (XRD) and vibration spectroscopic techniques. The Raman and infrared spectra of these compounds have been investigated, and their interpretation is discussed on both theoretical and experimental bases. Assignments have been deduced from the systematic investigation of pure compounds and isotopic species. A comparison of vibrational frequencies in La, Na, Gd, and Dy borophosphates reveals that the internal vibrations of the BO2and PO4ions shift to higher frequency with the decrement of lattice parameters from La to Dy, indicating a strengthening of the phosporus–oxygen and boron–oxygen bonding.

The crystal structure and magnetic properties of LaCoIii 13—xAlx compounds have been investigated by X-ray powder diffraction and magnetization measurement. X-ray powder diffraction shows that the compounds crystallize in cubic NaZn13-type structure with lattice parameter a = 11.345(2) to 11.473(4) Å in the range of x ≤ 2.7, and in the tetragonal Ce2Ni17Si9 structure at x = 3. Magnetization measurements reveal that both cubic and tetragonal LaCo13—xAlx are ferromagnetic with Curie temperature higher than 840 K, and the magnetic moment per Co atom in LaCo13—xAlx compounds decreases with Al content.

The BaB2O4–BaF2–2NaF–NaB2O4reciprocal system has been investigated by combination of experimental measurements with theoretical calculation. The Na2B2O4–2NaF binary and Na2B2O4–BaF2pseudo-binary phase diagrams are measured by means of DTA and X-ray diffraction. The thermodynamic functions for all sub-binary systems are derived from measured phase diagrams and thermodynamic data by CALPHAD technique, and the sub-binary phase diagrams are calculated according to phase equilibrium principle. Then, the thermodynamic functions for sub-binary systems are extrapolated to the BaB2O4–BaF2–2NaF–Na2B2O4reciprocal system, and the phase diagram of the reciprocal system is calculated. The calculated phase diagrams are verified by additional experiments.

We investigated the magnetic properties, corrosion resistance, and microstructure of Tb6Fe13Cu-added Nd–Fe–B sintered magnets through the magnetic measurement device, electrochemical method, and microstructure analysis. The results show that doping Tb6Fe13Cu can not only effectively improve the intrinsic coercivity but also significantly improve the corrosion resistance of the magnet. An intrinsic coercivity from 15.01 to 21.40 kOe is achieved in magnet by increasing the additive amounts of Tb6Fe13Cu to 3 wt%, while the remanence and the maximum energy product decreased slightly. It was also found that as the amount of addition increases, the corrosion potential of the magnet gradually becomes positive. Further investigations reveal that the remarkable enhancement in coercivity and corrosion resistance was owing to the formation of a Tb-rich (Nd, Pr, Tb)2Fe14B shell structure, the optimization in distribution/morphology of intergranular phases, and the more stable RE-rich phase.

Following increased environmental concerns on the toxicity of lead, the discovery of ultrahigh piezoelectricity in lead-free piezoelectric materials is critical for the substitution of commercial lead zirconate titanate (PZT) ceramics in numerous electronic devices. In this work, a synergistic design strategy is proposed to enhance the piezoelectricity in lead-free piezoelectric materials by flattening the Gibbs free energy density profile, via the coexistence of multiple phases and local structural heterogeneity. This strategic material design approach is based on first-principles calculations combined with Landau phenomenological theory and phase field simulations. Sustainable Stannum-doped BaTiO3lead-free ferroelectric ceramics are prepared to validate our proposed mechanism, and a giant piezoelectric coefficient d33 > 1100 pC/N is achieved, being the highest value reported in lead-free piezoceramics. The mechanism and paradigm of the excellent piezoelectricity achieved here provides a feasible solution for replacing lead-based piezoelectrics by lead-free counterparts.

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