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As an efficient converter between electromagnetic and mechanical energies, magnetostriction is an intriguing property for not only fundamental studies but also technological applications. However, the understanding of its microscopic origin remains challenging, which is critical for the development of magnetostriction materials. Here, the critical role of spin rotation in the giant magnetostriction of La(Fe,Al)13 is first revealed by the in-situ magnetic and temperature field of neutron powder diffraction. The giant magnetostriction originates from magnetic-field-driven spin moment rotation of canting structure, in which the sharp increase of ferromagnetic component causes the elongation of icosahedron inside of lattice. Furthermore, it is the first time to reveal the accurate canting antiferromagnetic structure in La(Fe,Al)13. The present study provides a new strategy, i.e., the spin rotation, for exploring new magnetostriction functional materials.

Lead-free Ba0.70Ca0.30TiO3 + x mol% MnO2 (abbreviated as BCTMx, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0 and 1.2) piezoelectric ceramics were synthesized by the solid-state reaction method. The effects of MnO2 additives on the phase transition, microstructure, dielectric, ferroelectric, strain behaviors and piezoelectric properties are investigated. BCTMx ceramics (x = 0–1.2) exhibit diphasic tetragonal and orthorhombic phases. The tetragonal phase is gradually suppressed by increasing x. As x increases from 0 to 1.2, the Curie temperature (TC) decreases monotonically from 128 to 45 °C, while the grain size, dielectric and ferroelectric properties increase and reach the maximum near x = 0.6. On the other hand, the piezoelectric coefficient (d33) and the electromechanical coupling coefficient (kp%) decrease simultaneously, whereas the mechanical quality factor (Qm), bipolar and unipolar strain increase and reach the maximum values of 684, 0.28% and 0.24%, respectively, near x = 0.6. The optimum electrical performance with $$\varepsilon_{r}$$ = 1323, tan $$\delta$$ = 0.08, TC = 66 °C, Pmax = 12.2 μC/cm2, Pr = 6.9 μC/cm2, EC = 13.3 kV/cm, d33 = 116 pC/N, kp% = 0.22%, Qm = 684 and the normalized strain $$d_{33}^{*}$$ = Smax/Emax as high as 480 pm/V were observed for x = 0.6. The high strain and Qm suggested that the MnO2-modified Ba0.70Ca0.30TiO3 ceramics are promising candidate for high power applications.

(1-x)[0.8Na0.5Bi0.5TiO3-0.2K0.5Bi0.5TiO3]-xBiMn2/3Nb1/3O3 ((1-x)NKBT-xBMN with x = 0–0.04) piezoceramics were prepared, the composition-dependent domain structure and domain switching under electric field and their effects on macroscopic electrical properties have been systematically investigated. At room temperature, though the ceramics persists rhombohedral-tetragonal mixed crystal structure, their domain structure evolves from dispersive island-like with average size of 80 nm for x = 0 to labyrinthian-like with average size of 120 nm for x = 0.0075, and then tends to be unobservable by forming polar nanoregions for x = 0.04. As the results, the x = 0.0075 ceramic shows enhanced ferroelectric and piezoelectric property. When compared with the x = 0 pristine counterpart, the saturated polarization, remnant polarization, piezoelectric coefficient, and electromechanical coupling factor of x = 0.0075 ceramic increase by 3%, 12%, 40%, and 20% to 43.2 μC/cm2, 31.2 μC/cm2, 147 pC/N, and 0.28. This work suggests that fine domain engineering is a promising way to further improve electrical property.

Composite ceramics based on non-stoichiometric 0.94Na0.48Bi0.44TiO3 (NBT-BT) and ZnO, (1-x)NBT-BT:xZnO with x = 0 ∼ 0.3 are prepared and investigated. The phase structure changes from tetragonal-dominated for x = 0 to rhombohedral-dominated for x > 0. The domain structure simultaneously evolves from nanodomain to macrodomain. At room temperature, the x = 0 ceramic has a pinched polarisation-electric field (P-E) loop, whereas x > 0 ceramics demonstrate square-shaped P-E loops with a maximum Pr of 30.6 μC/cm2 of x = 0.2. Moreover, ceramics with x = 0.1 and 0.2 have enhanced pyroelectric coefficients in a wide temperature range with full width at half maximums of 31 °C and 15.5 °C and peak values of 29.2 × 10−4 and 100.7 × 10−4 C/(m2·K), respectively. The results are explained based on the stress-induced room temperature relaxor-ferroelectric transition. This work affirms that forming composites is an effective way to tune the electrical properties of NBT-based materials.

Negative thermal expansion (NTE) has been found in some magnetic functional materials due to the magnetovolume effect (MVE), in which an order-to-disorder magnetic transition occurs. Here, we report an unconventional MVE which can induce the crossover from the common positive thermal expansion of the end members of ScFe2 and TiFe2 to the NTE in the solid solution of (Sc1−xTix)Fe2 (x = 0.6, αV = −28.36 × 10−6 K−1, 125–205 K). The direct evidence of neutron powder diffraction and first-principles calculations discloses that the decrease of intrinsic magnetic moments at the Fe(2a) site results in the ferromagnetic transition from one to another, which causes a stronger negative contribution to thermal expansion than the conventional MVE. The pair distribution function analysis verifies that the decrease in the nearest distance of Fe(6h)–Fe(6h) lying in the ab plane results in the shrinkage of the a(b) axis. The analysis of anisotropic atomic displacement parameters excludes the phonon induced NTE mechanism. Furthermore, an intriguing zero thermal expansion has been found in Sc0.55Ti0.45Fe2 (10–250 K). The present study provides an approach to achieve NTE or controllable thermal expansion, which may be used to enhance other magnetic-related effects, such as the magnetocaloric and barocaloric effect.

The 43-xFe-28Cr-23Co-3Mo-2V-1Zr-xY; x = 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 wt% permanent magnets were produced through casting, thermomagnetic annealing and aging treatments. Magnetic and microstructural properties were improved by Y addition and process optimization. The Y element modifies the morphology of ferromagnetic F-Co rich phase, introduces filed anisotropy and contributes in coercivity enhancement. XRD and EDS results showed that Y free 43Fe-28Cr-23Co-3Mo-2V-1Zr alloy is composed of Fe-Co-V (54.4%) and Cr-Mo-Zr (45.6%) phases while Y doped 41Fe-28Cr-23Co-3Mo-2V-1Zr-2Y alloy is consists of Fe-Co-V-Y (55.7%), Cr-Mo-Zr (29.3%) and Y1Co5 (15%) magnetic phases. Micrographs obtained by scanning transmission electron microscope elucidate nanostructural exchange coupled Fe-Co-V-Y (15–20 nm), Cr-Mo-Zr and Y1Co5 (10 nm) phases for 41Fe-28Cr-23Co-3Mo-2V-1Zr-2Y alloy. Pole figures and ODFs deduced sharp magnetic {1 1 0}〈0 0 1〉 textures or preferential orientation of Fe-Co rich rod like particles. Henkel plots deduced strong ferromagnetic exchange interactions between the magnetic phases. The 43Fe-28Cr-23Co-3Mo-2V-1Zr alloy yields Br of 0.71 T, Hc of 97 kA/m and (BH)max of 51.3 kJ/m3 which were remarkably improved to Br of 1.05 T, Hc of 130 kA/m and (BH)max of 61.6 kJ/m3 with 41Fe-28Cr-23Co-3Mo-2V-1Zr-2Y alloy.

The 47.5-xFe-28Cr-20Co-3Mo-1.5Ti-xM; M = Nb; x = 0.5, 1, 1.5, 2.0, 2.5, 3.0 (wt%) permanent magnets have been investigated after solution annealing, thermomagnetic annealing and step-aging process. Alloys were prepared by vacuum melting and casting technique. Magnets with improved properties were developed through a modified thermal treatment cycle. Solution annealed specimens depict equiaxed α phase grain size of 250 µm while optimally thermomagnetic treated and step aged magnets yield ultra-fine Fe-Co nanorods (10 nm) precipitates in Cr-Ti-Nb matrix. The Nb addition to 47.5Fe-28Cr-20Co-3Mo-1.5Ti alloy expands the α phase structure by suppressing the nonmagnetic phases at annealed state and promotes shape anisotropy for spinodal phases in final treated samples leading to the improvements of magnetic properties. Spinodal phases preferentially aligned and elongated close to applied field direction and retained strong Goss {1 1 0}〈0 0 1〉 orientations. The 45.5Fe-28Cr-20Co-3Mo-1.5Ti-2Nb magnet reveals Hc of 86.9 kA/m, Br of 1.24 T and (BH)max of 57 kJ/m3. High coercivity and remanence in the magnets are attributed to the ideal shape anisotropy of Fe-Co rich nanorods or nanowires.

Magnetic insulating and exchange bias (EB) are two basic magnetic states with actual and potential applications in spintronic and magnonic devices. However, ferromagnetic insulators (FMIs) are rare, and it is even more challenging to obtain a FMI with large EB. In this paper, high performance of FMIs and EB in $\mathrm{LaMn}{\mathrm{O}}_{3}$:NiO nanocomposite epitaxial thin films is reported. The antiferromagnetic NiO nanoparticles, randomly embedded in a ferromagnetic $\mathrm{LaMn}{\mathrm{O}}_{3}$ matrix, enhance the robustness of the insulating state and result in an EB field as large as 1100 Oe. The simultaneously enhanced resistivity and EB are attributed to localized oxygen vacancy, preserved strain state, and increased ferromagnetic-antiferromagnetic interface ratio. This paper provides not only a material candidate for spintronics but also a referential strategy to design artificial materials with multifunctionality.

Ferromagnetic insulators (FMIs) have received widespread attention for applications in novel low power consumption spintronic devices. Further optimizing robust ferromagnetic insulation and developing a multifunctional FMI by integrating other magnetic properties can not only ease or pave the way for actual application but also provide an additional degree of freedom for device design. In this work, by introducing antiferromagnetic CoO into the FMI LaMnO3, we constructed (1 − x)LaMnO3:xCoO composite thin films. The films simultaneously show robust FMI characteristics and a large exchange bias (EB). For the x = 0.5 sample, the resistivity is 120 Ω cm at 250 K, the magnetization is 100 emu cm−3, and the EB field is −2200 Oe at 10 K. In particular, the blocking temperature is up to 140 K. Synchrotron radiation x-ray absorption spectroscopy reveals the coexistence of Mn3+, Mn2+, Co2+ and Co3+, arising from interfacial charge transfer and space charge/defect trapping, which should be responsible for the enhanced and integrated multifunctional magnetic properties.

As one of the most pronounced structural features, polar nano-regions (PNRs) is believed to have significant contribution to the outstanding piezoelectric property of relaxor-based ferroelectrics. However, direct experimental investigation on the connection between the PNRs behavior under electric field and piezoelectric responses is still insufficient. In this work, by the combined use of piezoresponse force microscopy, polarization light microscopy, and the electrical property measurements, we investigate the structure evolution from macro-domains to PNRs around ferro-paraelectric phase transition temperature (Tm, 140 °C) in Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 single crystal. Most importantly, based on the corresponding analysis of unipolar strain-electric-field (S-E) curves at different temperatures and the direct observation of electric-field-induced structure evolution at Tm, we intensively investigate the response of PNRs to electric field and its contribution to piezoelectric property. We conclude that, under electric field, the active PNRs around Tm first serve as polar seeds to induce macro-domains from the non-polar matrix, then promote the switching of macro-domains. The large-field strain coefficient d33* in these two processes can achieve maximum of about 5410 pm/V and 61710 pm/V at Tm, and gradually decreases at higher temperature with lower PNRs content.

Further improving electromechanical properties and overcoming relatively low Curie temperature (Tc) of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-100xPT) are still two scientific issues. Here, we demonstrate a stable coexistence of monoclinic-tetragonal (MC-T) phases in ZnO-modified PMN-32PT (PMN-32PT:xZnO) due to the diffusion-induced substitution of Zn2+ for Mg2+. The Curie temperature, saturated polarization, remnant polarization, piezoelectric coefficient (Tc, Ps, Pr, d33) are increased from (160 °C, 22.0 μC/cm2, 13.3 μC/cm2, 350 pC/N) for x = 0 to (180 °C, 30.3 μC/cm2, 22.4 μC/cm2, 470 pC/N) for x = 0.06. Moreover, the thermal stability is improved. After annealing at 150 °C, the x = 0.06 sample shows retrained d33 value of 209 pC/N, about 4 times larger than that of x = 0 counterpart. The improved properties are attributed to the substituting increased polar nanoregions and easy domain switching in MC phase.

Nanocomposite hard magnets in the form of cones have been synthesized by rapid solidification process with Nd7.5Y2.7Fe62B22.3Nb3.1Cu2.4 alloy. X-ray diffraction studies deduced that as-cast alloys have a mixture of α-Fe, Fe3B, Nd2Fe14B and amorphous phase which, upon annealing, transformed into α-Fe, Fe3B and Nd2Fe14B magnetic phases. Transmission electron microscopy and three dimensional atom probe analysis elucidated a nanocrystalline microstructure consists of magnetically soft α-Fe, Fe3B and hard Nd2Fe14B nanograins. The good hard magnetic properties such as remanence (Br) of 0.45 T, coercivity (iHc) of 1315 kA/m and maximum energy product (BH)max of 56.7 kJ/m3 were obtained after annealing the Nd7.5Y2.7Fe62B22.3Nb3.1Cu2.4 alloy at 1013 K for 15 min. Henkel plot yielded the existence of strong inter-grain exchange interactions between magnetically soft and hard grains. High coercivity of 1315 kA/m for the optimally annealed Nd7.5Y2.7Fe62B22.3Nb3.1Cu2.4 alloy is ascribed to the large volume fraction of hard magnetic phase, high magnetocrystalline anisotropy and interface effects.

Due to the advantage of invariable length with temperatures, zero thermal expansion (ZTE) materials are intriguing but very rare especially for the metals based compounds. Here, we report a ZTE in the magnetic intermetallic compounds of Tb(Co,Fe)2 over a wide temperature range (123–307 K). A negligible coefficient of thermal expansion (αl = 0.48 × 10–6 K–1) has been found in Tb(Co1.9Fe0.1). Tb(Co,Fe)2 exhibits ferrimagnetic structure, in which the moments of Tb and Co/Fe are antiparallel alignment along the c axis. The intriguing ZTE property of Tb(Co,Fe)2 is formed due to the balance between the negative contribution from the Tb magnetic moment induced spontaneous magnetostriction and the positive role from the normal lattice expansion. The present ZTE intermetallic compounds are also featured by the advantages of wide temperature range, high electrical conductivity, and relatively high thermal conductivity.

Highly dispersed α-Al2O3 microplatelets of various sizes and aspect ratios were prepared by additive-assisted molten salt synthesis. The effects of SiO2 and SiO2 + CaO additions on phase formation and morphology development of α-Al2O3 particles were investigated. Introducing additives are very effective in controlling α-Al2O3 morphology. SiO2 additive significantly enhances shape anisotropy of α-Al2O3 platelets, where a particle aspect ratio ∼23.8 was achieved, about 2.7–6.0 times higher than those of the platelets prepared without additives. When using SiO2 + CaO mixture, low concentration additive facilitates the growth of large platelets (∼9.8 µm), while increasing its content dramatically reduces the platelet size to ∼3.7 µm. These findings provide a new insight for the design and synthesis of novel advanced anisotropic microcrystals with improved quality.

Two-dimensional multifunctional perovskite microcrystals are very important for various applications due to their unique shape-dependent properties. In this work, we reported a facile topochemical approach to synthesize SrTiO3 perovskite microplatelets with remarkably improved characteristics from Aurivillius Bi4Ti3O12 precursors. A stable Bi-containing intermediate phase was not formed during the Aurivillius to perovskite structure transformation, which facilitates the achievement of high phase/composition purity in the product and is easier than many previously reported topochemical reactions for perovskites. Different from the polycrystalline nature of the converted perovskites as reported previously, secondary recrystallization healed the substantial microstructural/crystalline damage induced during structural conversion, retaining the single-crystal memory of Bi4Ti3O12 in the converted SrTiO3 particles. Benefiting from subsequent epitaxial growth and rearrangement via Ostwald ripening, the SrTiO3 microplatelets exhibited more regular shapes and narrower size distributions than the precursors, instead of only closely resembling the precursor morphologies as reported previously. For the first time, local piezoelectricity was detected from the individual SrTiO3 microplatelets using a piezoelectric force microscope. In particular, the piezoelectric response parallel to the [001] direction was much higher than that detected perpendicular to it, possibly being associated with the orientation-dependent surface flexoelectric effect. This work offers a facile in situ topochemical strategy for fabricating other two-dimensional perovskite microcrystals and opens the door to expanding the potential application fields of SrTiO3 microplatelets.

SrZrO 3 modified and SrZrO 3 +MnO 2 co-modified 0.725BiFeO 3 −0.275BaTiO 3 : x SrZrO 3 + y MnO 2 (BF-BT: x SZ+ y MnO 2 , x , y = 0–0.075) multiferroic ceramics were prepared and the structure, resistance and multiferroic properties were comparatively investigated. SZ plays a more dominant role than MnO 2 in making a phase transition from rhombohedral to pseudocubic around x = 0.02, y = 0, which implies that SZ has formed solid solution with BF-BT whereas most Mn cations may have not entered into lattice of host but exist as second phase isolated particles. The modifications have complex effects on impedance spectra but the SZ-induced MPB has significantly increased resistance. As a result, such modifications show great effects on multiferroics. Briefly, the rhombohedral-pseudocubic morphotropic phase boundary composition shows peak ferroelectricity with remanent polarization of 8.2 μC/cm 2 and switchable remanent magnetization of 0.22 emu/g. Then the ferroelectricity and magnetism weaken slightly with increasing SZ contents. However, the introduction of MnO 2 results in monotonously suppressed ferroelectricity but enhanced magnetization. These results not only provide promising multiferroic material with switchable polarization and magnetization at room temperature, but also may stimulate further work on co-modified BF-BT solid solutions with optimized multiferroic properties.

Present work describes the manufacturing of Ni and Hf doped 60-xFe-27Cr-10Co-2Mo-1Ti-xM (M = Ni, Hf and 0.3 ≤ x ≤ 1.8 wt%) magnets produced through casting, magnetic aging and multistage tempering. Structural, magnetic and thermal properties of materials were systematically evaluated and discussed. Experimental results deduced that micro addition of nickel and hafnium elements tend to modify the morphology of magnetic phases in 60Fe-27Cr-10Co-2Mo-1Ti alloy leading to increase both magnetic and structural properties. Nickel improved intrinsic coercivity (Hcj) and magnetic induction (Br) for 60Fe-27Cr-10Co-2Mo-1Ti alloy. Hafnium addition to 58.8Fe-27Cr-10Co-2Mo-1Ti-1.2Ni alloy refines the microstructure and substantially improves coercivity (76.5kA/m) without insignificant change in magnetic induction. Optimal magnetic microstructure comprised nanostructured and 〈0 0 1〉 textured Fe-Co-Hf phase embedded in Cr-Mo-Ni-Ti as a matrix phase. Henkel plot evidenced existence of strong interphase magnetization interactions between Fe-Co-Hf and Cr-Mo-Ni-Ti phases. Magnetic measurements showed optimum magnetic properties such as Hcj = 51.8 kA/m Br = 1.18 T, Bs = 1.28 T and (BH)max = 38.8 kJ/m3 for 58.8Fe-27Cr-10Co-2Mo-1Ti-1.2Ni alloy which were remarkably enhanced to Hcj = 76.5 kA/m, Br = 1.2 T, Bs = 1.34 T, and (BH)max = 46 kJ/m3 for 57.9Fe-27Cr-10Co-2Mo-1Ti-1.2Ni-0.9Hf alloy.

Present work deduces the development of Nd3Pr3Fe67Co3Nb3Ti1B20 nanomagnets produced through magnetic annealing the amorphous precursors prepared through rapid solidification technique. Changes in structure and magnetic properties were investigated at as-cast and annealed stages. Results revealed that magnetic field annealing stimulates the kinetics of crystallization and modifies the structure and magnetic properties of the Nd3Pr3Fe67Co3Nb3Ti1B20 nanomagnets. Thermal analysis showed a glass transition temperature at 845 K and a crystallization temperature at 890 K for the alloy. X-ray diffraction studies demonstrated that as-cast alloy has amorphous structure while annealed magnet has multi-phase crystalline structure. Phase analysis elucidated that optimal annealed structure is compose of 34% Nd2Fe14B, 32% Pr2Fe14B, 21% α-Fe and 13% Fe3B phases. The HRTEM studies provoked that magnet microstructure consists of 55 nm Nd2Fe14B, 50 nm Pr2Fe14B, 24 nm α-Fe and 20 nm Fe3B magnetic grains which were interacted through ultra-thin grain boundaries. Henkel plot showed that grains of hard magnetic Nd2Fe14B (Pr2Fe14B) phase are coupled to grains of soft magnetic α-Fe (Fe3B) phase. Magnetic properties of nanocomposite magnets depend critically on the mass fraction of alloy constituent elements, casting conditions and heat treatment parameters. A small deviation of ±30 K from the ideal annealing temperature may affect the morphology of phases in the microstructure, which, in turn, influences the resultant magnetic properties of the final magnetic product. Optimal annealed Nd3Pr3Fe65Co3Nb3Ti1B20 rod magnet enunciated coercivity of 630 kA/m, remanence of 0.83 T and magnetic energy product of 84.3 kJ/m3. The present research work opens a new way to manufacture high performance magnetic components for advanced electronic devices, magnetic systems and magnetic recording media.

Here we report the 0.94(Bi0.5Na0.5)TiO3–0.06Ba(Zr0.055Ti0.945)O3 (0.94BNT–0.06BZT) lead-free ceramics was synthesized by two-step solid state reaction route. The structural, dielectric, ferroelectric, piezoelectric and electromechanical properties of the ceramics were studied, and showed excellent electric properties (P s = 39.9 μC/cm2, P r = 33.7 μC/cm2, E c = 2.79 kV/mm, S = 0.20%, d 33 = 174 pC/N, k p = 0.33). The depolarization temperature (T d ) of the ceramics is about 65 °C, which is determined from the first hump of relative dielectric constant. The electromechanical factor k p disappears at 65 °C, is consistent with the depolarization temperature (T d ) and the ferroelectric-antiferroelectric phase transition temperature (T fe−afe ) determined from the temperature-dependent P–E and bipolar S–E curves. These results indicate the 0.94BNT–0.06BZT ceramics has a good thermal stability in range of − 60–60 °C, and meets the actual demand.

The phase composition, magnetic and microstructural properties of Nd 2 Fe 14 B/(α-Fe, Fe 3 B) nanocomposite magnets produced by injection casting technique have been studied. Magnetic hysteresis loop of the Nd 7 Y 6 Fe 61 B 22 Mo 4 permanent magnet demonstrates the coercivity as high as 1289 kA/m. Electron microscopy elucidates a microstructure composed of magnetically soft α-Fe, Fe 3 B and hard Nd 2 Fe 14 B/Y 2 Fe 14 B nanograins (20–50 nm) separated by ultra-thin grain boundary layer. The Henkel plot curve of the Nd 7 Y 6 Fe 61 B 22 Mo 4 magnet yields the existence of exchange coupling interactions between soft and hard phases. Macroscopically large size sheet magnet is obtained due to high glass forming ability of the Nd 7 Y 6 Fe 61 B 22 Mo 4 alloy derived from large atomic radius mismatch and negative enthalpy of alloy constituent elements. The high coercivity of the magnet is attributed to the magnetically hard phase increment, nucleation of reverse domains and the presence of thin grain boundary phase. Good magnetic properties such as remanence of 0.51 T, coercivity of 1289 kA/m and maximum energy product of 46.2 kJ/m 3 are obtained in directly casted Nd 7 Y 6 Fe 61 B 22 Mo 4 sheet magnets.

Negative thermal expansion (NTE) is one of intriguing properties for solid compounds. Here we report structure and tunable negative thermal expansion in the (Hf1-xNbx)Fe2 magnetic alloys. The NTE mechanism has been investigated by a combined analysis of neutron powder diffraction, synchrotron X-ray diffraction, and macroscopic magnetic measurements. Direct experimental evidence shows that magnetovolume effect is the root of NTE of ferromagnetic phase, while the paramagnetic phase responds to the general positive thermal expansion (PTE). Especially, by adjusting the amount of Nb chemical substitution in (Hf1-xNbx)Fe2, the coexistence of NTE ferromagnetic and PTE paramagnetic phases can tune the large NTE (x = 0.05, αv = -23.13 × 10-6 K-1, 323~398 K) to the relatively low thermal expansion (x = 0.15, αv = -8.28×10-6 K-1, 173~323 K). The present study reveals the direct link between NTE and magnetic structure, and shows that thermal expansion could be tuned by the coexistence of magnetic and paramagnetic phases.

Bi0.5Na0.5TiO3-based incipient ferroelectrics with pseudocubic structure generally show weak ferro-/piezoelectricity but giant field-induced strains. It is difficult to artificially and smoothly improve the electrical property based on conventional chemical doping or substituting without changing the crystal structure and suppressing the strain. Here, by introducing the semiconductor ZnO into the lead-free incipient ferroelectric ((Bi0.5(Na0.84K0.16)0.5)0.96Sr0.04)(Ti0.975Nb0.025)O3 (BNT-2.5Nb) to form 0-3 type composites (BNT-2.5Nb:xZnO), we experimentally illustrate that the resistance and ferro-/piezoelectric properties can be enhanced significantly with an unchanged crystal structure and only slightly suppressed strains. For example, the remanent polarization and piezoelectric coefficient increase from 4.6 μC/cm2 and 8 pC/N for x = 0 to 9.0 μC/cm2 and 31 pC/N for x = 0.3. At the same time, the total strain only decreases from 0.140% for x = 0 to 0.108% for x = 0.3, whereas the negative strain increases from -0.003% for x = 0 to -0.010% for x = 0.3. And the thermal stability of d33 is enhanced. The corresponding mechanism is attributed to that ZnO can form a local field, preventing the depolarization of field induced macroscopic ferroelectric domains. Our results not only provide a feasible way to tune electrical properties of BNT-based incipient ferroelectrics, but also may stimulate further work on artificially-structured high performance ferroelectrics. This article is protected by copyright. All rights reserved.

Transition metal compounds with quasi-two-dimensional structure demonstrate a series of un-precedent quantum phases, such as topological insulator, topological phase transition under thermal/pressure stimuli, which is attributed to delicate interplay among interlayer coupling, spin-orbit coupling and stoichiometry. Here, Cu2TlSe2 and Cu2TlTe2 crystals were successfully synthesized by Bridgeman method. Highly crystalline quality of these samples is verified by X-ray diffraction and microstructural characterization. Temperature-dependent-Hall-resistivity shows that Cu2TlSe2 is hole-like and Hall resistivity is in-sensitive to temperature; while Hall resistivity of Cu2TlTe2 is positive at room temperature and change to negative at 30 K. Combined experimental results and electronic band structures calculated by first-principles method, it is revealed that Cu2TlSe2 is a metal, but Cu2TlTe2 is a semi-metal. This work demonstrates the rich physical phases of layered transition metal compounds under the interplay among interlayer coupling, spin-orbit coupling and stoichiometry.

The heterostructure interface provides a powerful platform for exploring rich emergent phenomena, such as interfacial superconductivity and nontrivial topological surface states. Here, SrRuO3/SrIrO3 superlattices were epitaxially synthesized. The magnetic and magneto-transport properties of these superlattices were characterized. A broad cusp-type splitting in the zero-field-cooling/field-cooling temperature-dependent magnetization and magnetization relaxation, which follows the modified stretched function model, accompanied by double hysteresis magnetization loops were demonstrated. These physical effects were modulated by the SrIrO3 layer thickness, which confirms the coexistence of interfacial spin glass and ferromagnetic ordering in the superlattices. In addition, the topological Hall effect was observed at low temperatures, and it is weakened with the increase of the SrIrO3 layer thickness. These results suggest that a noncoplanar spin texture is generated at the SrRuO3/SrIrO3 interfaces because of t...

The study of ZrTe 5 is revived because theory predicts the quantum spin Hall effect in monolayer ZrTe 5 and topological phase in bulk ZrTe 5 . To study the topological property of ZrTe 5 , the growth of large size and high-quality single crystals is the first and crucial step. Here, by mean of iodine (I 2 ) transport agent, centimeter-sized ZrTe 5 single crystals were successfully grown by the chemical vapor transport technique. The microstructure characterization reveals that grown ZrTe 5 crystal has “stacking stripes of wood” morphology, and growth mechanism is proposed accordingly. The size of grown ZrTe 5 crystals can be reached as large as 35×2×0.5 mm 3 , which enable us to measure the a -, b - and c - axis anisotropic resistance. Large and single crystalline ZrTe 5 crystals provide a solid basis for exploring its topological phase.

To investigate the reason for the reduction in damage resistance of In x Ga1−x N with increasing indium (In) content, we used molecular dynamics methods to simulate the threshold displacement energies, the individual recoil damage and the overlapping cascade processes in In x Ga1−x N (x = 0.3, 0.5, 0.7) during ion implantation. The average threshold displacement energy of In x Ga1−x N decreases a little (from 41.0 eV to 34.6 eV) as the In content increases (from 0.3 to 0.7) and the number of defects produced by individual cascades increases less than 30% with increasing In content (from 0.3 to 0.7), while the overlapping cascade simulations showed that with In content increasing the dynamic annealing processes in cascades were significantly suppressed. Thus, the suppression of dynamic annealing in the cascades is the main reason for the reduction of damage resistance of In x Ga1−x N by adding In content. The analysis of defect distribution during overlapping cascades showed that defects in In-rich In x Ga1−x N (x = 0.7) agglomerate more rapidly as the irradiation dose increases and are likely to form large clusters, which are harder to anneal during cascade evolution. Therefore, the suppression of dynamic annealing in In-rich In x Ga1−x N can be attributed to the rapid agglomeration of defects with the irradiation dose.

High-pressure experiments usually expect a hydrostatic condition, in which the physical properties of materials can be easily understood by theoretical simulations. Unfortunately, non-hydrostatic effect is inevitable in experiments due to the solidification of the pressure transmitting media under high pressure. Resultantly, non-hydrostaticity affects the accuracy of the experimental data and sometimes even leads to false phenomena. Since the non-hydrostatic effect is extrinsic, it is quite hard to analyze quantitatively. Here, we have conducted high pressure experiments on the layered BiCuXO (X = S and Se) single crystals and quantitatively analyzed their pronounced non-hydrostatic effect by high throughput first-principles calculations and experimental Raman spectra. Our experiments find that the BiCuXO single crystals sustain the tetragonal structure up to 55 GPa (maximum pressure in our experiment). However, their pressure-dependent Raman shift and electric resistance show anomalous behaviors. Through optimization of thousands of crystal structures in the high throughput first-principles calculations, we have obtained the evolution of the lattice constants under external pressures, which clearly substantiates the non-hydrostatical pressure exerted in BiCuXO crystals. Our work indicates that the high throughput first-principles calculations could be a handy method to investigate the non-hydrostatic effect on the structural and electronic properties of materials in high pressure experiments.

Multiferroic ceramics of 0.675BiFe1−x Cr x O3–0.325PbTiO3 (x = 0, 0.01, 0.025, 0.05) were prepared and comparatively investigated. The rhombohedral–tetragonal morphotropic phase boundary (MPB) was formed in 0.675BiFeO3–0.325PbTiO3. The B-site Cr-substitution changes the structure from MPB to rhombohedral phase gradually, accompanied with monotonously decreased ferroelectric Curie temperature and average grain size. More interestingly, Such Cr-substitution enhances room temperature ferroelectric and magnetic properties simultaneously. The underlying mechanism is mainly attributed to the substitution enhanced local Fe3+–Cr3+ magnetic interaction and the suppressed oxygen vacancy effect. We believe these results are helpful supplements for optimizing structures and room temperature multiferroic properties of BiFeO3-based materials.

(Ba 0.95 Ca 0.05 )(Ti 0.94 Sn 0.06 )O 3 - x mol% CuO ceramics were fabricated to investigate their domain structures and piezoelectric properties. The CuO additive significantly improved the densification behavior of the ceramics, resulting in a reduced sintering temperature by ~150 °C. Increasing x shifted the orthorhombic-tetragonal phase transition towards lower temperatures, and caused the specific ratio of tetragonal to orthorhombic phase to increase at room temperature. The herringbone domain patterns became much simpler and their number substantially decreased. The watermarks and parallel strips are the dominant domain configuration in ceramics with x =0.50 which show the optimum piezoelectric properties: d 33 ~516 pC/N, d 33 * ~996 pC/N, k p ~0.42, and Q m ~352. The underlying physical mechanisms for the enhanced piezoelectricity in the CuO-doped ceramics were discussed.

KxRhO2, as an isomorphism material to NaxCoO2, is theoretically predicted to have rich physical properties. In this letter, we studied the chemical depotassiation process of K0.62RhO2 crystals to obtain KxRhO2 with x varied from 0.32 to 0.62. And an end-product K0.32RhO2 with single phase determined through XRD refinement belongs to space group P63/mmc (No. 194). Electrical transport, magneto-resistant transport and Hall measurements substantiate that K0.32RhO2 is a multi-band normal metal, which can be well described by Landau Fermi liquid theory. Our finding sheds more light on the preparation and transport properties of layered oxides.

Ferroelectric/polar semiconductor BaTiO3:xZnO composites (BT:xZnO) have been prepared and investigated. The ZnO particles distribute at the BT grain boundaries to form 0–3 type composites, i.e., the isolated 0-dimensional ZnO particles are embedded in the 3-dimensional BT matrix. With increasing ZnO content, the Curie temperature keeps constant, however, both the dielectric constant and ferroelectric polarization of the composites increase, reaching the maximum at x=0.3, and then tend to decrease. Furthermore, the composite has improved temperature stability of ferroelectric polarization and field-induced strain up to ~100 °C. It is believed that ZnO can induce a built-in electric field which has influence on the domain switching and thus on the observed composition- and temperature-dependent electrical properties. This work may provide some new clues for developing ferroelectric composites with high performance.

Compounds with the layered perovskite-like structure are well-known engineering materials because of the multifunctionality. In this work, a novel La3-xEuxTi2TaO11 (0 ≤ x ≤ 0.45) solid-solution with a typical layered perovskite-like structure was synthesized via the traditional solid-state reaction ceramic technique. The optimal emission happened in La3-xEuxTi2TaO11 (x = 0.3). To modify the luminescence properties, La2.7Eu0.3Ti2-5y/4Ta1+yO11 (y = 0.04, 0.05, 0.08, 0.1, 0.12, 0.14) phosphor was developed via stoichiometric alteration of (Ta5+→Ti4+) in “B” sites. The research motivation is on the fact that the framework distortion due to cation-disorders is an efficient method to modify the luminescence and improve the thermal stability of a rare earth ion (RE)-activated phosphor. The phase formations were conducted by XRD measurements and Rietveld refinements. The morphology was characterized by SEM and EDS. The luminescence properties such as luminescence, emission excitation wavelength, and decay lifetimes showed a dependence on the distortion of the framework. Cation alteration of (Ta5+→Ti4+) in La3-xEuxTi2TaO11 (x = 0.03–0.45) greatly modified the red-luminescence activities, such as improved efficiency, pure red chromaticity, and thermal stability. The excess of Ta5+ on Ti4+ sites bring about the distortion of octahedron surrounding resulting in intensive changes in the crystal-field environment around Eu3+ activators. The framework distortion due to substitutions of multiple cations is effective to enhance the emission efficiencies and thermal stability of RE3+-activated phosphors. The cation-disorder was discussed via luminescence features in 5D0→7F0 transition region. The results are helpful to introduce Eu3+ as a probe for rare-earth dopant site microstructure in phosphor materials.

Recent studies discovered that the binary transition-metal compounds ${A}_{x}{B}_{y}$ demonstrate extremely large magnetoresistance (XMR) under magnetic field $B$, for example, ${10}^{6}%$ in $\mathrm{PtB}{\mathrm{i}}_{2}$ and ${10}^{5}%$ in $\mathrm{WT}{\mathrm{e}}_{2}$. The underlying physical origins, however, are quite diverse, such as electron-hole balance, backscattering forbidden of Dirac/Weyl fermions, and high mobility. Here we experimentally find an ideal compound ($\ensuremath{\alpha}\ensuremath{-}\mathrm{W}{\mathrm{P}}_{2}$) where the perfect electron-hole compensation can be sustained within a large temperature range (from 2 to 100 K). The XMR of $\ensuremath{\alpha}\ensuremath{-}\mathrm{W}{\mathrm{P}}_{2}$ is measured as high as $8.74\ifmmode\times\else\texttimes\fi{}{10}^{5}%$ under 9 T $B$ at 2 K, but it is remarkably decreased from $8.74\ifmmode\times\else\texttimes\fi{}{10}^{5}%$ to 18% when the temperature is raised from 2 to 100 K; simultaneously, the mobility is decreased by more than two orders of magnitude. Magnetotransport characterizations show that MR is proportional to ${B}^{2}$ and the pronounced dHvA quantum oscillations come from the conventional Schr\"odinger fermions in $\ensuremath{\alpha}\ensuremath{-}\mathrm{W}{\mathrm{P}}_{2}$, which rules out the possibility of Dirac fermions. These evidences strongly suggest that XMR observed in binary ${A}_{x}{B}_{y}$ semimetals is mainly attributed to high mobility, rather than Dirac/Weyl fermions, or resonant electron-hole compensation. This work elucidates the underlying physical origin of XMR in these compounds.

The study of $\mathrm{ZrT}{\mathrm{e}}_{5}$ crystals is revived because of the recent theoretical prediction of topological phase in bulk $\mathrm{ZrT}{\mathrm{e}}_{5}$. However, the current conclusions for the topological character of bulk $\mathrm{ZrT}{\mathrm{e}}_{5}$ are quite contradictory. To resolve this puzzle, we here identify the Berry phase on both $b$- and $c$ planes of high-quality $\mathrm{ZrT}{\mathrm{e}}_{5}$ crystals by the Shubnikov--de-Hass (SdH) oscillation under tilted magnetic field at 2 K. The angle-dependent SdH oscillation frequency, both on $b$- and $c$ planes of $\mathrm{ZrT}{\mathrm{e}}_{5}$, demonstrates the two-dimensional feature. However, phase analysis of SdH verifies that a nontrivial \ensuremath{\pi}-Berry phase is observed in the $c$-plane SdH oscillation, but not in the $b$-plane one. Compared to bulk Fermi surface predicted by the first-principle calculation, the two-dimensional-like behavior of SdH oscillation measured at $b$ plane comes from the bulk electron. Based on these analyses, it is suggested that bulk $\mathrm{ZrT}{\mathrm{e}}_{5}$ at low temperature (\ensuremath{\sim}2 K) belongs to a weak topological insulator, rather than Dirac semimetal or strong topological insulator as reported previously.

(Fe1 − xCox)68Dy6B22Nb4 (x = 0–0.5) bulk metallic glasses (BMGs) were prepared by copper mold casting. Effects of substituting Fe with Co on the thermal, magnetic and mechanical properties of the BMGs were investigated. Addition of Co is effective in improving the glass forming ability (GFA) of the alloy and BMG rods with diameters up to 4 mm can be obtained by industry-grade raw materials. The substitution of Co for Fe leads to high saturation magnetic flux density (0.7515 T) as a result of optimized number of spin-up and spin-down electrons in the d-band. The amorphous nature of the alloy gives rise to low crystalline anisotropy and coercivity (

Single phase BiFeO3 and Bi2Fe4O9 powders have been synthesized via hydrothermal method by carefully controlling the reaction conditions. It is found that the BiFeO3 shows dense microstructure with irregular, larger grains, the average grain size is ~5.0 μm, whereas the Bi2Fe4O9 displays small, porous microstructure with the sheet shaped grains, the average thickness is ~55 nm and length is ~500 nm. X-ray photoemission spectra confirm that in both compositions, the Bi and Fe cations have the charge valence of +3. The magnetization–magnetic field (M–H) and magnetization–temperature (M–T) measurements reveal that the BiFeO3 has weak ferromagnetism even at room temperature due to its canted antiferromagnetic interaction, whereas the Bi2Fe4O9 shows antiferromagnetic nature in the temperature range of 10–300 K. Our results provide interesting supplements for controlling the morphology and understanding the structure–property relationship of BiFeO3 and Bi2Fe4O9.

The magnetic properties, phase evolution and microstructure of Fe70−xMxB19Nd7Nb4 (M=Si, Gd, Si+Gd; x=0–2.5 at%) bulk nanocomposite permanent magnets in the form of rods produced by annealing the amorphous precursor have been investigated systematically. Microstructural examination, three-dimensional atom probe microanalysis, δM-plots, X-ray diffraction analysis and magnetometer studies deduced that good magnetic properties in the magnets originate from the homogenous microstructure consisting of exchange coupled, soft magnetic (α-Fe, Fe3B) and hard magnetic (Nd,Gd)2Fe14B nanophases. Optimally annealed Fe70B19Nd7Nb4 rod magnets exhibit magnetic properties of Br=0.61 T, iHc=876 kA/m and (BH)max=50.2 kJ/m3. Gadolinium and silicon addition to quaternary Fe70B19Nd7Nb4 alloy increased the mass fraction of hard magnetic phase, strengthened the exchange coupling interactions and enhanced the magnetic properties. Gadolinium and silicon segregated into hard magnetic phase which led to enhance coercivity up to 1115 kA/m. Enhancement in the coercivity is mainly resulted by hard phase increment as well as domain wall pinning, while strengthening of exchange coupling is caused by grain size refinement and increase in Curie temperature of the magnetic phases. The Fe67B19Nd7Gd2Nb4Si1 magnetic rods of 1.2 mm in diameter demonstrated the best magnetic properties such as intrinsic coercivity, iHc of 1115 kA/m, remanence, Br of 0.57 T and maximum energy product, (BH)max of 65.7 kJ/m3.

In this paper, BiCuSeO single crystals are successfully grown by a flux method at different growth temperatures (690 °C, 730 °C and 775 °C). The crystal surface morphology, microstructure, chemical composition and electrical properties are systematically characterized. By changing the growth temperature, the growth mechanism evolution, from dislocation-driven spiral growth mode to two-dimensional layer-by-layer mode, is observed due to the different growth supersaturations. Simultaneously, the temperature-dependent resistance confirms the electrical property changes from semiconductor to metal. Chemical analysis proves that BiCuSeO crystals grown at higher temperatures (730 °C and 775 °C) are slightly non-stoichiometric. The present results demonstrate the possibility of modulating the crystal morphology and electrical properties of BiCuSeO by controlling the supersaturation. This method may be applicable to similar compounds (BiCuOCh (Ch = S, Te)).

Relaxor based ternary (0.60 − x)Pb(In1/2Nb1/2)O3–0.40Pb(Mg1/3Nb2/3)–xPbTiO3 ((0.60 − x)PIN–0.40PMN–xPT) polycrystalline ceramics were synthesized by two-step columbite precursor method. The effects of PIN/PT content on phase structure, microstructure, density, and dielectric, piezoelectric, ferroelectric and pyroelectric properties of the ternary ceramics were systematically investigated. A morphotropic phase boundary (MPB) near x = 0.34 was identified by X-ray diffraction and further confirmed by their respective electrical properties. Piezoelectric, ferroelectric and pyroelectric properties were enhanced for compositions near the MPB. The 0.26PIN–0.40PMN–0.34PT ceramics show optimum electrical properties: piezoelectric coefficient d 33 = 505 pC/N, planar electromechanical coupling factor k p = 62.5 %, remnant polarization P r = 32.1 μC/cm2, coercive field E c = 8.8 kV/cm, and room temperature pyroelectric coefficient p = 0.050 μC/cm2 °C. In addition, the rhombohedral–tetragonal phase transition temperature T rt and Curie temperature T c of the ternary ceramics were identified by the temperature dependence of dielectric and pyroelectric measurements, which are much higher than those of binary PMN–PT ceramics, indicating the expanded temperature usage range of the ternary ceramics. The results show that this ternary system is a promising candidate for electromechanical applications with high performance and wide temperature usage range.

Magnetoresistance (MR) is the magnetic field-induced change of electrical resistance. The MR effect not only has wide applications in hard drivers and sensors but also is a long-standing scientific issue for complex interactions. Ferromagnetic/ferrimagnetic oxides generally show negative MR due to the magnetic field-induced spin order. We report the unusually giant positive MR up to 17,200% (at 2 K and 7 T) in 12-nm Sr2CrWO6 thin films, which show metallic behavior with high carrier density of up to 2.26 × 1028 m-3 and high mobility of 5.66 × 104 cm2 V-1 s-1. The possible mechanism is that the external magnetic field suppresses the long-range antiferromagnetic order to form short-range antiferromagnetic fluctuations, which enhance electronic scattering and lead to the giant positive MR. The high mobility may also have contributions to the positive MR. These results not only experimentally confirm that the giant positive MR can be realized in oxides but also open up new opportunities for developing and understanding the giant positive MR in oxides.

The asymmetric electron dispersion in type-II Weyl semimetal theoretically hosts anisotropic transport properties. Here, we observe the significant anisotropic Adler-Bell-Jackiw (ABJ) anomaly in the Fermi-level delicately adjusted WTe_{1.98} crystals. Quantitatively, C_{W}, a coefficient representing the intensity of the ABJ anomaly along the a and b axis of WTe_{1.98} are 0.030 and 0.051 T^{-2} at 2 K, respectively. We found that the temperature-sensitive ABJ anomaly is attributed to a topological phase transition from a type-II Weyl semimetal to a trivial semimetal, which is verified by a first-principles calculation using experimentally determined lattice parameters at different temperatures. Theoretical electrical transport study reveals that the observation of an anisotropic ABJ along both the a and b axes in WTe_{1.98} is attributed to electrical transport in the quasiclassical regime. Our work may suggest that electron-doped WTe_{2} is an ideal playground to explore the novel properties in type-II Weyl semimetals.

The domain evolution of 0.9625Bi 0.5 Na 0.5 TiO 3 −0.0375BiZn 0.5 Ti 0.5 O 3 ceramic is studied by piezoelectric force microscopy. Nanodomains are the most common in the as-prepared ceramic, and they can transform to monodomain in a micrometer-scale grain under a large external electric field, which corresponds to a maximum piezoelectric d 33 coefficient. After the field is removed, the mondomain commonly decomposes gradually, and occasionally it transforms to periodic stripe-like domains. This experiment exhibits the domain evolution during poling and depoling processes of a normal ferroelectric ceramic, which is different from ergodic relaxors.

Photoacoustic (PA) spectroscopy was used to study the properties of BaY $$_{2}$$ Si $$_{3}$$ O $$_{10}$$ :Ce $$^{3+}$$ phosphorous material with various doping concentrations. The PA amplitude and phase spectra, UV-vis absorption spectra, and excitation and emission spectra of BaY $$_{2}$$ Si $$_{3}$$ O $$_{10}$$ :xCe $$^{3+}$$ ( $$x\!= (5, 7,\; \hbox {and}\;9$$ ) mol%) were measured, and the influence of different doping concentrations on the spectral characteristics was analyzed. Moreover, by combining the PA amplitude and phase spectra measurements, a new method to characterize the relative luminescence quantum efficiency of phosphorous materials was proposed. The feasibility of this method was further demonstrated by fluorescence emission spectra measurements.

Er-doped 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (BNT-6BT: xEr, x is the molar ratio of Er 3+ doping) lead-free piezoceramics with x = 0–0.02 were prepared and their multifunctional properties have been comprehensively investigated. Our results show that Er-doping has significant effects on morphology of grain, photoluminescence, dielectric, and ferroelectric properties of the ceramics. At room temperature, the green (550 nm) and red (670 nm) emissions are enhanced by Er-doping, reaching the strongest emission intensity when x = 0.0075. The complex and composition-dependent effects of electric poling on photoluminescence also have been measured. As for electrical properties, on the one hand, Er-doping tends to flatten the dielectric constant-temperature (er-T) curves, leading to temperature-insensitive dielectric constant in a wide temperature range (50°C–300°C). On the other hand, Er-doping significantly decreases the ferroelectric-relaxor transition temperature (TF–R) and depolarization temperature (Td), with the TF–R decreasing from 76° Ct o 42°C for x= 0– 0.02. As a result, significant composition-dependent electrical features were found in ferroelectric and piezoelectric properties at room temperature. In general, piezoelectric and ferroelectric properties tend to become weaker, as confirmed by the composition-dependent piezoelectric coefficient (d33), planar coupling factor (kp), and the shape of polarization-electric field (P–E), current-electric field (J–E), bipolar/unipolar strain-electric field (S–E) curves. Furthermore, to understand the relationship between the TF–R/Td and the electrical properties, the composition of x = 0.0075 has been intensively studied. Our results indicate that the BNT-6BT: xEr with appropriate Er-doping may be a promising multifunctional material with integrated photoluminescence and electrical properties for practical applications.

(001) oriented SrBi 4 Ti 4 O 15 (SBT) microplatelets with Aurivillius-type crystal structure were fabricated by molten salt synthesis. The effects of flux type selection and salt-to-oxide ratio variation on crystallization habit and morphology of the product were investigated. The sodium salt fluxes facilitate the formation of Sr 2 Bi 4 Ti 5 O 18 large size platelets (≥17 µm in length), while potassium salt fluxes create favorable condition for the growth of small size SrBi 4 Ti 4 O 15 platelets (≤5 µm in length). When using KCl flux, a higher salt-to-oxide ratio is beneficial to produce smaller SBT platelets with relatively narrow size distribution. The ferroelectricity and piezoelectricity of an individual SBT platelet were examined by piezoelectric force microscopy. These microcrystals are suitable template candidate to achieve highly textured ceramics for high temperature applications.

A series of Gd-doped Sr2IrO4 single crystals were grown using a flux method. Analysis of the temperature-dependent resistance of these crystals reveals that these samples show two-dimensional weak localization at 150 to 300 K, while three-dimensional variable range hopping (VRH) behavior is observed at temperatures lower than 150 K. Two localization lengths are observed in the VRH behavior, with a transition temperature of around 88 K. Correspondingly, temperature-dependent magnetization observations along the ab-plane reveal magnetic anomalies at both 150 and 85 K. This work demonstrates the correlation between the electrical and magnetic properties of 5d transition-metal compounds.