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Thermoelectric technology allows conversion between heat and electricity. Many good thermoelectric materials contain rare or toxic elements, so developing low-cost and high-performance thermoelectric materials is warranted. Here, we report the temperature-dependent interplay of three separate electronic bands in hole-doped tin sulfide (SnS) crystals. This behavior leads to synergistic optimization between effective mass (m*) and carrier mobility (μ) and can be boosted through introducing selenium (Se). This enhanced the power factor from ~30 to ~53 microwatts per centimeter per square kelvin (μW cm−1 K−2 at 300 K), while lowering the thermal conductivity after Se alloying. As a result, we obtained a maximum figure of merit ZT (ZTmax) of ~1.6 at 873 K and an average ZT (ZTave) of ~1.25 at 300 to 873 K in SnS0.91Se0.09 crystals. Our strategy for band manipulation offers a different route for optimizing thermoelectric performance. The high-performance SnS crystals represent an important step toward low-cost, Earth-abundant, and environmentally friendly thermoelectrics.

The crystal structure, dynamics, magnetic structure and property of orthochromites solid solution Ho1−xYxCrO3 (x = 0, 0.2,…,1.0) were systematically investigated by X-ray diffraction, Raman scattering, magnetometry and neutron powder diffraction. With increasing non-magnetic Y3+-substitution for Ho3+ throughout the whole range, the crystallographic parameters remain almost unchanged, so is Neel temperature (TN ≈ 141 K), which is closely related to the structure in these orthochromites. However, the Raman spectra demonstrates the lattice dynamics is influenced due to the mass difference between Ho3+ and Y3+. Moreover, the spin reorientation property is also strongly affected by Y-substitution revealed by neutron powder diffraction. For the composition of x ≤ 0.6, the magnetism of Cr3+ sublattice adopts Γ2 spin configuration in terms of Bertaut notation from low temperature (10 K) up to Neel temperature. With the doping concentration further increases to x = 0.7 and 0.8, the system exhibits a mixed structure of (Γ2 + Γ4) within a certain temperature range. Beyond and underneath of which, a single spin configuration is identified as Γ4 (GxAyFz) and Γ2 (FxCyGz), respectively. After x = 0.8, only Γ4 (GxAyFz) are observed below TN. These phenomena are attributed to the weakened Ho3+-Cr3+ interaction with Y-substitution, which causes a competition between Γ2 and Γ4 spin configurations.

Mn-doped transition metal perovskites have shown versatile magnetic phenomena, and research on these materials has been revived in recent decades. Many controversies over the microscopic spin configuration remain unsolved, presumably due to the complicated spin and orbit interactions, which are strongly coupled with each other and sensitive to structural and chemical modulation. Here, the Mn-doped orthochromite YCrO3 was investigated to shed some light on this issue. The orthochromite YCr1-xMnxO3 (0 ≤ x ≤ 0.6) was synthesized and studied by X-ray diffraction, magnetometry and neutron powder diffraction. For x = 0.2–0.5 samples, the Cr3+ (Mn3+) sublattice adopts a Γ4 (Gx,Ay,Fz) antiferromagnetic structure with a canted ferromagnetic component. Negative magnetization behavior is observed for the x = 0.1 and 0.2 samples, which is suppressed and reversed by the applied magnetic field. As the doping concentration further increases to x = 0.6, the system exhibits a distinct spin-glass behavior below a spin-freezing temperature. These phenomena are attributed to the competition between weakened antiferromagnetic Cr3+-Cr3+ interactions and enhanced ferromagnetic Cr3+-Mn3+ interactions with Mn3+-doping. This work provides deep insights into understanding the complicated magnetic phenomena in Mn-doped correlated transition metal oxides.

The temperature dependent magnetism of Fe-doped rare earth orthochromite HoCr 1-x Fe x O 3 (x = 0, 0.2) was investigated by neutron powder diffraction. It is found that the magnetism of Cr(Fe) 3+ can be well understood within mean field theory, while the ordering of Ho 3+ was induced by the Cr(Fe) 3+ sublattice and can be satisfyingly described by an effective S = 1/2 model. The absences of both the most common G x F z configuration of Cr 3+ and the ordering of Ho 3+ caused by Ho-Ho interaction evidence a strong Ho 3+ -Cr 3+ interaction which dominates this system. On the other hand, a remarkable magnetoelastic strain was observed accompanying the Cr(Fe) 3+ ordering. An analysis based on the equation of state with a Gruneisen approximation was performed and revealed magnetic origin of this strain.

Cement hydration is a key process to determine most properties of cementitious materials. A deep understanding of cement hydration is thus favourable for the improvement of the overall properties of these materials and for providing solutions to the technique problems for concrete applications in terms of durability and sustainability. The conversion of water states is a fundamental process associated with cement hydration. Quasi-elastic neutron scattering (QENS) has recently emerged as a powerful non-destructive technique for studying the conversion of water states during cement hydration. The free water index and correlation parameters describing the states of the bound water and confined water can be quantitatively given. Compared with conventional methods of cement hydration characterization, QENS has a unique advantage. This paper summarizes the application of QENS for hydration in cement-based materials. In this review, the focus is first placed on the mechanism of the QENS method and the development of QENS spectrum analysis models to provide insight into the new technique. Then, the focus is shifted to its application for hydration and hydration kinetics in cement-based materials. Recent improvements in QENS facilities have allowed unexpected possibilities for studying complex hydration processes in cementitious materials. The potential of this promising technology for further research is outlined.

Orthoferrite solid solution HoFe1−xCrxO3 (x=0, 0.2,…,1.0) was synthesized via solid state reaction methods. The crystal structure, magnetism and spin reorientation properties of this system were investigated by X-ray diffraction, neutron powder diffraction and magnetic measurements. For compositions of x≤0.6, the system exhibits similar magnetic properties to HoFeO3. With increasing Cr-doping, the system adopts a Γ4(GxAyFz) magnetic configuration with a decreased Neel temperature from 640 K to 360 K. A Γ42 spin reorientation of Fe(Cr)3+ was also observed in this system with an increase in transition temperature from 56 K to about 200 K due to competition between the Fe(Cr)–Fe(Cr) and Ho–Fe(Cr) interactions. For the x≥0.8, the system behaves more like HoCrO3 which adopts a Γ2(FxCyGz) configuration with no spin reorientation below the Neel temperature TN. Throughout the whole substitution range, we found that the saturated moment of Fe(Cr) was less than the ideal value for a free ion, which implies the existence of spin fluctuation in this system. A systematic magnetic structure variation with Cr-substitution is revealed by Rietveld refinement. A phase diagram combining the results of the magnetic measurements and neutron powder diffraction results was obtained.

We report a systematic crystal growth and characterization of Ca$_{1-y}$La$_{y}$Fe$_{1-x}$Ni$_{x}$As$_{2}$, the newly discovered 112-type iron-based superconductor. After substituting Fe by a small amount of Ni, bulk superconductivity is successfully obtained in high quality single crystals sized up to 6 mm. Resistivity measurements indicate common features for transport properties in this 112-type iron pnictide, suggest strong scattering from chemical dopants. Together with the superconducting transition temperature $T_c$, and the Neel temperature $T_N$ determined by the elastic neutron scattering, we sketch a three-dimensional phase diagram in the combination of both Ni and La dopings., Comment: 8 pages, 8 figures

We report a spin reorientation from Γ4(Gx, Ay, Fz) to Γ1(Ax, Gy, Cz) magnetic configuration near room temperature and a re-entrant transition from Γ1(Ax, Gy, Cz) to Γ4(Gx, Ay, Fz) at low temperature in TbFe1−xMnxO3 single crystals by performing both magnetization and neutron diffraction measurements. The Γ4 − Γ1 spin reorientation temperature can be enhanced to room temperature when x is around 0.5 ~ 0.6. These new transitions are distinct from the well-known Γ4 − Γ2 transition observed in TbFeO3, and the sinusoidal antiferromagnetism to complex spiral magnetism transition observed in multiferroic TbMnO3. We further study the evolution of magnetic entropy change (−ΔSM) versus Mn concentration to reveal the mechanism of the re-entrant spin reorientation behavior and the complex magnetic phase at low temperature. The variation of −ΔSM between a and c axes indicates the significant change of magnetocrystalline anisotropy energy in the TbFe1−xMnxO3 system. Furthermore, as Jahn-Teller inactive Fe3+ ions coexist with Jahn-Teller active Mn3+ ions, various anisotropy interactions, compete with each other, giving rise to a rich magnetic phase diagram. The large magnetocaloric effect reveals that the studied material could be a potential magnetic refrigerant. These findings expand our knowledge of spin reorientation phenomena and offer the alternative realization of spin-switching devices at room temperature in the rare-earth orthoferrites.

We performed measurements of specific heat and inelastic neutron scattering on Pr(Fe1-xCox)4P12 to investigate the effects of d-electron doping on the heavy fermion (HF) state and non-magnetic order state of PrFe4P12. The ordered state is suppressed by the Co substitution. A Schottky type behavior in the specific-heat appears at 8 K, in contrast with the undoped system. The inelastic neutron spectrum of the Co substituted system is composed of several sharp inelastic peaks, in contrast with the quasi-elastic spectrum in the HF phase of PrFe4P12. The experimental results indicate that the Co substitution induces localized 4f electrons of Pr ions with suppression of the HF state and the exotic ordering.

The metal-nonmetal transition in Ce- and Rh-substituted ${\text{PrRu}}_{4}$${\text{P}}_{12}$ was investigated through magnetic susceptibility, x-ray superlattice reflection, and inelastic neutron scattering (INS) measurements. The saturation in the magnetic susceptibility at low temperatures suggests a singlet ground state for Pr sites in both compounds. This finding is in contrast to the staggered order of singlet and triplet ground states found in the ordered phase of ${\text{PrRu}}_{4}$${\text{P}}_{12}$, which leads to a diverging susceptibility. The intensities of x-ray superlattice reflections of both compounds develop below 45 K and decrease rapidly below 10 K with a simultaneous decrease in electrical resistivity. INS experiments reveal that 4$f$ electron states in both compounds change drastically from two distinct crystal field (CF) level schemes corresponding to an order parameter in the multipole ordered phase (10 $\text{K}lTl45$ K) to a nearly uniform CF level scheme below 10 K. The uniform CF ground state at the Pr sites carries no degree of freedom relevant to the staggered ordering pattern and electronic gap formation. Therefore, the substituted systems exhibit a reentrant metallic state at the lowest temperature. These phenomena may originate from effective electron doping due to atomic substitution.

We performed inelastic neutron scattering experiment to investigate a role of 4f electrons in the M–I transition of PrRu 4 P 12 at T M – I = 63 K . Below about 20 K, there are resolution-limited sharp excitations represented by two kinds of crystal-field schemes of Pr ions due to the low-temperature superlattice formation. With increasing temperature, the excitation peaks shift and broaden considerably. Such drastic evolution of the crystal-field excitations in PrRu 4 P 12 indicates strong hybridization between 4f and conduction electrons.

Variation of electronic state in the metal-nonmetallic phase transition of PrRu 4 P 12 has been investigated by a polarized neutron diffraction experiment. Two Pr ions placed at the center and the corner sites in the bcc unit cell surrounded by smaller and larger Ru-ion cubic sublattices have Γ 1 and Γ 4 ( 2 ) crystal field (CF) ground states, respectively. This modulated electronic state as well as the drastic evolution of the CF schemes of Pr ions in the nonmetal phase can be explained by p–f hybridization combined with the nesting behavior of Fermi surface with the wave vector q = ( 1 , 0 , 0 ) .

Strong hybridization between conduction electrons and f 2 electrons in a trivalent Pr ion is a recent attractive subject. For example, the Pr-filled skutterudite compounds have been extensively studied. Pr(Ru 1- x Rh x ) 4 P 12 exhibits the reentrant-like behavior of the metal-nonmetal transition, and PrFe 4 P 12 the heavy-fermion state followed by the nonmetallic ordering. In this article, we review briefly these phenomena characterized by the staggered structures of the totally symmetric order parameters of f 2 state. We also demonstrate the higher-order magnetic scattering of polarized neutron to investigate quantum state levels in the f electron systems, which is expected to be carried out at the pulsed neutron facility J-PARC MLF.

Dynamics of rare-earth ions in filled skutterudite compounds PrT4Sb12 (T = Ru and Os) has been investigated by a neutron inelastic scattering technique. We found an optical mode located at extremely low energy around 4 meV exhibiting apparent softening behavior by 10 - 30% from 300 to 10 K. This softening mode is attributed to the motion of the filled Pr ions bound in anharmonic potential within the Sb cage. In addition, quasielastic responses near the Brillouin zone center indicate relaxation modes. These features can be explained in terms of a mode coupling scenario involving the motion of the filled Pr ions with huge amplitude.