Halide Anions Tuning of Lead-Free Perovskite-Type Ferroelectric Semiconductors with Inverse High-Temperature Symmetry Breaking.

There is a noticeable gap in the literature regarding research on halogen-substitution-regulated ferroelectric semiconductors featuring multiple phase transitions. Here, a new category of 1D perovskite ferroelectrics (DFP)2 SbX5 (DFP+ = 3,3-difluoropyrrolidium, X- = I- , Br- , abbreviated as I-1 and Br-2) with twophase transitions (PTs) is reported. The first low-temperature PT is a mmmFmm2 ferroelectric PT, while the high-temperature PT is a counterintuitive inverse temperature symmetry-breaking PT. By the substitution of iodine with bromine, the Curie temperature (Tc) significantly increases from 348 K of I-1 to 374 K of Br-2. Their ferroelectricity and pyroelectricity are improved (Ps value from 1.3 to 4.0 µC cm-2 , pe value from 0.2 to 0.48 µC cm-2  K-1 for I-1 and Br-2), while their optical bandgaps increased from 2.1 to 2.7 eV. A critical slowing down phenomenon is observed in the dielectric measurement of I-1 while Br-2 exhibits the ferroelastic domain. Structural and computational analyses elucidate that the order-disorder movement of cations and the distortion of the chain perovskite [SbX5 ]2- anions skeleton lead to PT. The semiconductor properties are determined by [SbX5 ]2- anions. The findings contribute to the development of ferroelectric semiconductors and materials with multiple PTs and provide materials for potential applications in the optoelectronic field.

Feasibility study on cardiac resynchronization in the treatment of heart failure by single left bundle branch pacing.

To examine the feasibility of single left bundle branch pacing for cardiac resynchronization therapy (CRT) by carrying out a frequency adaptive atrioventricular delay (RAAVD) algorithm and automatic optimization of the single left bundle branch pacing atrioventricular interval (AVI) based on the right atrioventricular interval (RAS-RVS). Thirty-six patients with CRT class Ia indications according to the European Society of Cardiology 2016 guidelines and implanted with RAAVD functional three-chamber pacemakers were prospectively enrolled in this study. Patients were divided into a single left bundle branch pacing group (n = 21) and a standard biventricular pacing group (n = 15). The optimization of the two groups was performed under standard cardiac colour Doppler ultrasound, followed by the comparison of the QRS width, cardiac function improvement, and echocardiography indicators. The ratio of AVI to the right atrial-right ventricular interval (RAS-RVS) after single LV pacing optimization was defined as the single left bundle branch pacing coefficient (LUBBPε). In comparison to the BVP, the QRS was significantly narrowed (P = 0.017), accompanied by a significantly increased proportion of patients with NYHA class I and II, as well as the 6MWT. Compared with standard biventricular pacing, LVEDD was significantly shortened (P = 0.045), accompanied by significantly improved LAD, AVVTI, EA distance/RR, IVMD, and TS-SD after the operation. RAS-RVS was 156 ± 33 ms, the optimized AVI was 102 ± 10 ms, and LUBBPε was calculated to be 0.66 ± 0.06. Depending on the LUBBPε, a three-chamber pacemaker with a single left bundle branch pacing system was developed based on RAS-RVS-optimized AVI automatically. A three-chamber pacemaker with single left bundle branch pacing can achieve CRT based on RAS-RVS, reaching the optimal AVI of 66% of RAS-RVS.

Enhanced Electrocaloric Effect of Lead Scandium Tantalate by Zirconium Doping.

The electrocaloric effect (ECE) is a novel technology that offers high efficiency and environmental friendliness, making it suitable for solid-state refrigeration applications. Among the extensively studied ECE materials, lead scandium tantalate (PST) stands out for its excellent performance. However, its applications are restricted by its narrow working temperature range. To overcome this limitation, we explore the enhancement of the ECE through zirconium ion doping. We synthesized PbSc0.5-0.5xTa0.5-0.5xZrxO3 samples (x = 0, 0.025, 0.05, 0.075). The introduction of zirconium ions led to an increase in the Curie temperature from 28.9 °C (x = 0) to 55.5 °C (x = 0.075). Additionally, the relaxation factor γ of the ceramics increased from 1.40 (x = 0) to 1.59 (x = 0.075). The temperature span (Tspan) exhibited a rising trend with increasing x, reaching 10.9 K at x = 0.075. The maximum temperature change (ΔTmax) was observed at x = 0.025, with a value of 1.94 K. X-ray diffraction (XRD) patterns revealed that zirconium ion doping influenced the B-site ordering degree, thereby regulating the ECE. To further validate the results, we employed direct measurements and thermodynamic calculations. Overall, the regulation of ionic ordering through zirconium doping effectively enhances the ECE performance. These findings contribute to the development of advanced materials for solid-state refrigeration technologies.

A room temperature ferroelectric material with photoluminescence: (1,3-dicyclohexylimidazole)2MnCl4.

Molecular ferroelectric materials have been widely used in capacitors and sensors due to their low cost, light weight, flexibility and good biocompatibility. Organic-inorganic hybrid complexes, on the other hand, have received a great deal of attention in the luminescence field due to their low cost and simple preparation. The combination of ferroelectricity and photoluminescence in organic-inorganic hybrid materials not only leads to tunable optical properties, but also enriches potential applications of multifunctional ferroelectrics in optoelectronic devices. Here, we report a new luminescent ferroelectric material (1,3-dicyclohexylimidazole)2MnCl4 (DHIMC). Thermogravimetric analysis (TGA) was used to measure the mass change of the material at a measurement rate of 20 K min-1 from room temperature to 900 K, and we found that this material has good thermostability, which is up to 383 K. Meanwhile, UV-vis measurements showed that it is also a fluorescent material emitting a strong green fluorescence at the wavelength of 525 nm. The ferroelectricity of the crystal was determined by two different methods: the Sawyer-Tower method and the double-wave method (DWM). Particularly, the single crystal experiences a phase transition from the ferroelectric phase to the paraelectric phase during the heating/cooling process at 318 K/313 K and the space group changes from P1̄ (centrosymmetric) to P1 (non-centrosymmetric). This work will enrich multifunctional luminescent ferroelectric materials and their application in display and sensing.

Lead-Free Hybrid Organic-Inorganic Ferroelectric: (3,3-Difluoropyrrolidinium)2ZnCl4·H2O.

Hybrid organic-inorganic ferroelectrics (HOIFs) have a wide range of applications in the optoelectronic field in terms of rich optoelectronic properties. Particularly, lead-free HOIFs have attracted extensive attention due to their environmental friendliness, low heavy metal toxicity, and low synthesis cost. However, there are few reports about Zn-based HOIFs due to their uncontrollable ferroelectric synthesis and other reasons. Here, we designed and synthesized a zinc-based zero-dimensional (3,3-difluoropyrrolidine)2ZnCl4·H2O (DFZC) single crystal, which undergoes a phase transition from ferroelectric to paraelectric phase (space group from Pna21 to Pnma) at 295.5 K/288.9 K during the heating/cooling process. The systematic study shows that the ferroelectric phase transition is a displacive type. The ferroelectric hysteresis loop of DFZC was obtained by the double-wave method and the Sawyer-Tower method, which has a spontaneous polarization (Ps) of ∼0.4 µC/cm2. This work reveals the strategy to design new zinc-based lead-free HOIFs for potential applications in optoelectronic fields.

Left univentricular pacing for cardiac resynchronization therapy using rate-adaptive atrioventricular delay.

OBJECTIVE: To evaluate left univentricular (LUV) pacing for cardiac resynchronization therapy (CRT) using a rate-adaptive atrioventricular delay (RAAVD) algorithm to track physiological atrioventricular delay (AVD). METHODS: A total of 72 patients with congestive heart failure (CHF) were randomized to RAAVD LUV pacing versus standard biventricular (BiV) pacing in a 1: 1 ratio. Echocardiography was used to optimize AVD for both groups. The effects of sequential BiV pacing and LUV pacing with optimized A-V (right atrio-LV) delay using an RAAVD algorithm were compared. The standard deviation (SD) of the S/R ratio in lead V1 at five heart rate (HR) segments (RS/R-SD5), defined as the "tracking index," was used to evaluate the accuracy of the RAAVD algorithm for tracking physiological AVD. RESULTS: The QRS complex duration (132 ± 9.8 vs. 138 ± 10 ms, P < 0.05), the time required for optimization (21 ± 5 vs. 50 ± 8 min, P < 0.001), the mitral regurgitant area (1.9 ± 1.1 vs. 2.5 ± 1.3 cm2, P < 0.05), the interventricular mechanical delay time (60.7 ± 13.3 ms vs. 68.3 ± 14.2 ms, P < 0.05), and the average annual cost (13,200 ± 1000 vs. 21,600 ± 2000 RMB, P < 0.001) in the RAAVD LUV pacing group were significantly less than those in the standard BiV pacing group. The aortic valve velocity-time integral in the RAAVD LUV pacing group was greater than that in the standard BiV pacing group (22.7 ± 2.2 vs. 21.4 ± 2.1 cm, P < 0.05). The RS/R-SD5 was 4.08 ± 1.91 in the RAAVD LUV pacing group, and was significantly negatively correlated with improved left ventricular ejection fraction (LVEF) (ΔLVEF, Pearson's r = -0.427, P = 0.009), and positively correlated with New York Heart Association class (Spearman's r = 0.348, P = 0.037). CONCLUSIONS: RAAVD LUV pacing is as effective as standard BiV pacing, can be more physiological than standard BiV pacing, and can decrease the average annual cost of CRT.