Zero Thermal Expansion and Semiconducting Properties in PbTiO3-Bi(Co, Ti)O3 Ferroelectric Solid Solutions

Zero thermal expansion (ZTE) behavior is rare but important for both fundamental studies and practical applications of functional materials. Until now, most available ZTE materials are either electrical insulating oxides or conductive metallic compounds. Very few ZTE materials exhibit the semiconductor feature. Here we report a ZTE in a semiconducting ferroelectric of 0.6PbTiO₃-0.4Bi(Co_0.55Ti_0.45)O_3-δ. Its unit cell volume exhibits a negligible change over a broad temperature range from room temperature to 500 °C. The ZTE is supposed to be correlated with the spontaneous volume ferroelectronstriction. Intriguingly, the present ZTE material also exhibits the semiconducting characteristic accompanied by negative temperature coefficient of resistance. The mechanism of electric conduction is attributed to the electronic hopping from one ion (Ti³⁺) to another (Ti⁴⁺). The semiconductor nature has also been confirmed by the noticeable visible-light absorption with the relatively lower band gap (E_g) value of 1.5 eV, while the ferroelectric property can be well-maintained with large polarization. The first-principles calculations reveal that the drastically narrowed E_g is related to the Co-Ti substitution. The present multifunctional material containing ZTE, semiconducting, and ferroelectric properties is suggested to enable new applications such as the substrate for solar conversion devices.

Composite Yttrium-Carbonaceous Spheres Templated Multi-Shell YVO4 Hollow Spheres with Superior Upconversion Photoluminescence

Complex oxide YVO₄ multi-shell hollow spheres with uniform morphologies and controllable shell numbers are successfully prepared by using a newly developed and general composite yttrium-carbonaceous sphere templated approach. The prominent upconversion luminous intensity of the YVO₄ :Yb³⁺ /Er³⁺ hollow spheres might be attributed to the enhanced near-infrared excitation light harvesting efficiency originated from the multiple reflections.

Tunable thermal expansion in framework materials through redox intercalation

Thermal expansion properties of solids are of fundamental interest and control of thermal expansion is important for practical applications but can be difficult to achieve. Many framework-type materials show negative thermal expansion when internal cages are empty but positive thermal expansion when additional atoms or molecules fill internal voids present. Here we show that redox intercalation offers an effective method to control thermal expansion from positive to zero to negative by insertion of Li ions into the simple negative thermal expansion framework material ScF₃, doped with 10% Fe to enable reduction. The small concentration of intercalated Li ions has a strong influence through steric hindrance of transverse fluoride ion vibrations, which directly controls the thermal expansion. Redox intercalation of guest ions is thus likely to be a general and effective method for controlling thermal expansion in the many known framework materials with phonon-driven negative thermal expansion.

The positive thermal expansion exhibited by most materials at increased temperatures is a severe issue for many high precision applications. Here, Xing and co-workers show that redox intercalation of Li ions into a ScF₃ framework offers effective control of the thermal expansion for this simple material.

Anomalous dispersion X-ray diffraction study of Pb/Bi ordering/disordering states in PbTiO3-based perovskite oxides

Synchrotron radiation-based anomalous dispersion X-ray powder diffraction (ADSPD) was carried out to reveal the Pb/Bi ordering/disordering states in a series of PbTiO₃-based negative thermal expansion materials (1 - x)PbTiO₃ - xBiFeO₃ (x = 0.1, 0.3, 0.5) and (1 - x)PbTiO₃ - xBi(Zn_1/2Ti_1/2)O₃ (x = 0.1, 0.2, 0.3). It gives strong evidence of the disordered Pb/Bi distributions in these compositions, which is consistent with electron diffraction studies. Combined with binding energy calculation, we show that the disordered nature of Pb/Bi distributions is likely to be attributed to the similar electron configurations of Pb²⁺ and Bi³⁺ as well as their comparable coordinate environments in perovskite structures. The results of this study may be helpful to better understand the structure-property relationship in Pb/Bi-containing perovskites and are useful for further developing underlying physics in relevant materials.

Spring-like motion caused large anisotropic thermal expansion in nonporous M(eim)2(M = Zn, Cd)

Spring-like thermal motion caused large anisotropic thermal expansion in nonporous coordination polymers.

Local structure and controllable thermal expansion in the solid solution (Mn1−xNix)ZrF6

Controllable thermal expansion in the cubic solid solutions of (Mn_1−xNi_x)ZrF₆through atomic linkage flexibility.

Preparation and characterization of high Curie-temperature piezoelectric ceramics in a new Bi-based perovskite of (1 − x)PbTiO3-xBi(Zn1/2Hf1/2)O3

The increasing trend of T_C is non-monotonic, which corresponds well with that of c/a in the (1 − x)PbTiO₃-xBi(Zn_1/2Hf_1/2)O₃ solid solutions.

PbTiO3-based perovskite ferroelectric and multiferroic thin films

Ferroelectric thin films, especially PbTiO₃-based perovskite thin films which possess robust spontaneous electrical polarization, are widely investigated and applied in various devices.

Local Structural Distortion Induced Uniaxial Negative Thermal Expansion in Nanosized Semimetal Bismuth

The corrugated layer structure bismuth has been successfully tailored into negative thermal expansion along c axis by size effect. Pair distribution function and extended X-ray absorption fine structure are combined to reveal the local structural distortion for nanosized bismuth. The comprehensive method to identify the local structure of nanomaterials can benefit the regulating and controlling of thermal expansion in nanodivices.

Giant Polarization and High Temperature Monoclinic Phase in a Lead-Free Perovskite of Bi(Zn0.5Ti0.5)O3-BiFeO3

Lead-free piezoelectrics have attracted increasing attention because of the awareness of lead toxicity to the environment. Here, a new bismuth-based lead-free perovskite, (1 - x)Bi(Zn_0.5Ti_0.5)O₃-xBiFeO₃, has been synthesized via a high-pressure and high-temperature method. It exhibits interesting properties of giant polarization, morphotropic phase boundary (MPB), and monoclinic phase. In particular, large tetragonality (c/a = 1.228) and giant spontaneous polarization of 110 μC/cm² has been obtained in 0.6 Bi(Zn_0.5Ti_0.5)O₃-0.4BiFeO₃, which is much higher than most available lead-free materials and conventional Pb(Zr,Ti)O₃. MPB is clearly identified to be constituted of tetragonal and monoclinic phases at x = 0.5. Notably, a single monoclinic phase has been observed at x = 0.6, which exhibits an intriguing high-temperature property. The present results are helpful to explore new lead-free MPB systems in bismuth-based compounds.

Near-Zero Thermal Expansion and High Ultraviolet Transparency in a Borate Crystal of Zn4 B6 O13

Intrinsic isotropic near-zero thermal expansion is discovered in borate crystal Zn₄ B₆ O₁₃ with high transparency in the ultraviolet region. First-principles calculations demonstrate that the very low thermal expansion originates mainly from the invariability of the solid [B₂₄ O₄₈ ] truncated octahedra that are fixed by the [Zn₄ O₁₃ ] clusters in the ZBO structure.

Thermal Expansion Anomaly in TTB Ferroelectrics: The Interplay between Framework Structure and Electric Polarization

Tetragonal tungsten bronze (TTB) makes up a large family of functional materials with fascinating dielectric, piezoelectric, or ferroelectric properties. Understanding the thermal expansion mechanisms associated with their physical properties is important for their practical applications as well as theoretical investigations. Fortunately, the appearance of anomalous thermal expansion in functional materials offers a chance to capture the physics behind them. Herein, we report an investigation of the thermal expansion anomalies in TTBs that are related to ferroelectric transitions and summarize recent progress in this field. The special role of Pb(2+) cation is elucidated. The interplay between the thermal expansion anomaly, electric polarization, and framework structure provides new insight into the structure-property relationships in functional materials.

Large negative thermal expansion in non-perovskite lead-free ferroelectric Sn2P2S6

Functional materials showing both negative thermal expansion (NTE) and physical performance, such as ferroelectricity and magnetism, have been extensively explored in the past decade. However, among ferroelectrics a remarkable NTE was only found in perovskite-type PbTiO3-based compounds. In this work, a large NTE of -4.7 × 10(-5) K(-1) is obtained in the non-perovskite lead-free ferroelectric Sn2P2S6 from 243 K to TC (338 K). Structure refinements and first-principle calculations reveal the effects of the Sn(ii) 5s-S 3p interaction on spontaneous polarization and its correlation with NTE. Then the mechanism of spontaneous volume ferroelectrostriction (SVFS) is verified and it could well elucidate the nature of NTE in ferroelectric Sn2P2S6. This is the first case to demonstrate the unusual NTE behavior by SVFS in a non-perovskite lead-free ferroelectric material.

Hydration and Thermal Expansion in Anatase Nanoparticles

A tunable thermal expansion is reported in nanosized anatase by taking advantage of surface hydration. The coefficient of thermal expansion of 4 nm TiO2 along a-axis is negative with a hydrated surface and is positive without a hydrated surface. High-energy synchrotron X-ray pair distribution function analysis combined with ab initio calculations on the specific hydrated surface are carried out to reveal the local structure distortion that is responsible for the unusual negative thermal expansion.

Association of a type 2 diabetes genetic risk score with insulin secretion modulated by insulin sensitivity among Chinese Hans

Type 2 diabetes (T2D) is characterized by insulin resistance and impaired insulin secretion. The present study aimed to identify the influence of insulin sensitivity on the genetic risk of impaired insulin secretion among a Chinese Han population. For 3229 controls and 1994 treatment-naïve T2D, single nucleotide polymorphisms (SNPs) from 24 T2D-related genomic loci were genotyped and a genetic risk score (GRS) was constructed. Results showed that GRS was associated with insulin secretion and disposition indices in both controls and treatment-naïve T2Ds. Upon stratifying the participants into tertiles by the Matsuda index, we observed an inhibitory relationship between the GRS and insulin secretion in low insulin sensitive but not in high insulin sensitive controls and treatment-naïve T2Ds. Moreover, low insulin sensitive individuals exhibited more severe impairment in insulin secretion and beta cell response to insulin sensitivity with an increase in risk alleles. Our findings identified that the association of GRS with insulin secretion was strongly modulated by insulin sensitivity in both controls and T2Ds of Chinese Han. It indicates that insulin sensitization should be emphasized in prevention and treatment of T2D for beta cell protection.

Establishment of a normal reference value of parathyroid hormone in a large healthy Chinese population and evaluation of its relation to bone turnover and bone mineral density

A normal reference value of parathyroid hormone (PTH) was established for the first time in a large sample of healthy Chinese subjects by completely excluding interference of vitamin D deficiency. A high PTH level correlated significantly with an elevated bone turnover and a reduced bone mineral density (BMD).

INTRODUCTION

The aims of this study are to establish a normal reference value for serum PTH and to evaluate the effect of parathyroid gland status on bone turnover and BMD.

METHODS

Our cross-sectional study included 1436 healthy individuals from 5 different Chinese cities. Concentrations of serum PTH, 25-hydroxyvitamin D (25OHD), procollagen I N-terminal peptide (P1NP, a bone formation marker), and carboxyl-terminal telopeptide of type I collagen (β-CTX, a bone resorption marker) were measured by electrochemiluminescence immunoassay. BMD was measured by dual-energy X-ray absorptiometry. The relation of PTH concentration to age, gender, height, and weight was examined. Reference values of PTH were established for all subjects and for subjects categorized by serum 25OHD concentrations. Correlations of PTH levels with bone turnover biomarkers and BMD were statistically analyzed.

RESULTS

Reference values of PTH were 8.84-69.95 pg/mL in all the subjects and 7.48-60.73 and 5.83-56.78 pg/mL in the subjects with serum 25OHD concentrations of ≥20 and ≥30 ng/mL, respectively. Serum PTH showed a negative linear correlation with 25OHD, and the breakpoint was 18.21 ng/mL, below which the PTH level rapidly increased. The increase in PTH levels with age showed a positive linear correlation with P1NP and β-CTX concentrations and a negative linear correlation with BMD at the lumbar spines and the femoral neck.

CONCLUSIONS

A reference value of PTH was established in a large sample of healthy Chinese subjects according to 25OHD status, gender, and age. A high PTH level correlated significantly with an elevated bone turnover and a reduced BMD.

Novel mutations of CLCN7 cause autosomal dominant osteopetrosis type II (ADO-II) and intermediate autosomal recessive osteopetrosis (IARO) in Chinese patients

SUMMARY

Osteopetrosis is a group of genetic bone disorders. Mutations in the chloride channel 7 gene (CLCN7) lead to chloride channel defect, which results in autosomal dominant osteopetrosis type II (ADO-II), autosomal recessive osteopetrosis (ARO), and intermediate autosomal recessive osteopetrosis (IARO). In the present study, we identified seven novel mutations of the CLCN7 gene and reported the first case of IARO with compound heterozygous mutation in Chinese population.

INTRODUCTION

Osteopetrosis is a heritable bone disorder due to the deficiency of or function defect in osteoclasts. Mutations in the CLCN7 lead to chloride channel defects, which result in osteopetrosis with diverse severity ranging from asymptomatic or relatively mild symptoms in ADO-II to the very severe phenotype in ARO. Heterozygous mutations in CLCN7 are associated to ADO-II, while homozygous and compound heterozygous mutations in CLCN7 may result in ARO and IARO. To date, a total of 24 mutations in CLCN7 were identified in ADO-II, and only 3 mutations were identified in IARO. In the present study, we reported seven unrelated ADO-II patients and one IARO patient from Chinese population and elucidated the characteristics of CLCN7 gene mutations in these patients.

METHODS

All 25 CLCN7 exons and exon-intron boundaries from genomic DNA were amplified and sequenced in eight affected individuals suffering from ADO-II/IARO. The clinical, biochemical, and radiographic analysis were evaluated to compare the differences between ADO-II and IARO both in genotype and phenotype.

RESULTS

The results showed that there were seven novel CLCN7 mutations identified in these ADO-II/IARO patients, including six heterozygous missense mutations (p.L224R, p.S290Y, p.R326G, p.G347R, p.S473N, and p.L564P) and a novel splice mutation (p.K691FS).

CONCLUSIONS

The compound heterozygous mutations (p.L224R and p.K691FS) were firstly observed in one IARO patient. The present study would enrich the database of CLCN7 mutations and improve our understanding of this heritable bone disorder.