Gauge to simultaneously determine the electrical conductivity, the Hall constant, and the Seebeck coefficient up to 800 °C

A new high temperature gauge to simultaneously determine the electrical conductivity, the Hall constant, and the Seebeck coefficient has been developed. Screen-printed heating structures on a ceramic sample holder are used to generate temperatures up to 800 ∘C by Joule heating. The heating structures were designed using the finite element method (FEM) simulations and the temperature distribution was validated by thermal imaging. To measure the Seebeck coefficient, Au/Pt thermocouples with different geometries were investigated and successfully integrated into the gauge. Measurements on constantan, a typical Seebeck coefficient reference material with high electrical conductivity, high charge carrier concentration, and a known Seebeck coefficient, as well as on a well-described boron-doped silicon wafer confirm the functionality of the gauge up to 800 ∘C.</p

Enhanced control of self-doping in halide perovskites for improved thermoelectric performance

Metal halide perovskites have emerged as promising photovoltaic materials, but, despite ultralow thermal conductivity, progress on developing them for thermoelectrics has been limited. Here, we report the thermoelectric properties of all-inorganic tin based perovskites with enhanced air stability. Fine tuning the thermoelectric properties of the films is achieved by self-doping through the oxidation of tin (ΙΙ) to tin (ΙV) in a thin surface-layer that transfers charge to the bulk. This separates the doping defects from the transport region, enabling enhanced electrical conductivity. We show that this arises due to a chlorine-rich surface layer that acts simultaneously as the source of free charges and a sacrificial layer protecting the bulk from oxidation. Moreover, we achieve a figure-of-merit (ZT) of 0.14 ± 0.01 when chlorine-doping and degree of the oxidation are optimised in tandem

Optimization of a sensor for a Tian–Calvet calorimeter with LTCC-based sensor discs

In this work, it is shown how a finite element method (FEM) model of a Tian–Calvet calorimeter is used to find improvements in the sensor design to increase the sensitivity of the calorimeter. By changing the layout of the basic part of the sensor, which is a low temperature co-fired ceramics (LTCC) based sensor disc, an improvement by a factor of 3 was achieved. The model was validated and the sensors were calibrated with a set of measurements that were later used to determine the melting enthalpies and melting temperatures of indium and tin samples. Melting temperatures showed a maximum deviation of 0.2 K while the enthalpy was measured with a precision better than 1 % for most samples. The values for tin deviate by less than 2 % from literature data

Synthesis, Solid State Structure and Spectro-Electrochemistry of Ferrocene-Ethynyl Phosphine and Phosphine Oxide Transition Metal Complexes

The synthesis of ferrocene-ethynyl phosphine platinum dichloride complexes based on (FcCtriple bond; length of mdashC)nPh3−nP (1a, n = 1; 1b, n = 2; 1c, n = 3; Fc = ferrocenyl, (η5-C5H5)(η5-C5H4)Fe) is described. Air-oxidation of 1c afforded (FcCtriple bond; length of mdashC)3Pdouble bond; length as m-dashO (6). Treatment of 1a–1c with [(PhCtriple bond; length of mdashN)2PtCl2] (2) or [(tht)AuCl] (tht = tetrahydrothiophene) (7), respectively, gave the heterometallic transition complexes cis-[((FcCtriple bond; length of mdashC)nPh3−nP)2PtCl2] (3a, n = 1; 3b, n = 2; 3c, n = 3) or [((FcCtriple bond; length of mdashC)nPPh3−n)AuCl] (8a, n = 1; 8b, n = 2). Further treatment of these molecules with HCtriple bond; length of mdashCMc (4a, Mc = Fc; 4b, Mc = Rc = (η5-C5H5)(η5-C5H4)Ru) in the presence of [CuI] produced trans-[((FcCtriple bond; length of mdashC)Ph2P)2Pt(Ctriple bond; length of mdashCFc)2] (5) (reaction of 3a with 4a) and [(FcCtriple bond; length of mdashC)nPh3−nPAuCtriple bond; length of mdashCMc] (n = 1: 9a, Mc = Fc; 9b, Mc = Rc; n = 2: 11a, Mc = Fc; 11b, Mc = Rc) (reaction of 4a, 4b with 8a, 8b), respectively.The structures of 3a, 5, 6, 8, 9a, and 9b in the solid state were established by single-crystal X-ray structure analysis. The main characteristic features of these molecules are the linear phosphorus–gold–acetylide arrangements, the tetra-coordination at phosphorus and the square-planar surrounding at platinum.The electrochemical and spectro-electrochemical behavior of complexes 5, 8a, 9a, 9b and [(Ph3P)AuCtriple bond; length of mdashCFc] was investigated in the UV/Vis/NIR. Near IR bands that are likely associated with charge transfer from the ((FcCtriple bond; length of mdashC)Ph2P)2Pt or the ((FcCtriple bond; length of mdashC)nPh3−nP)Au (n = 0, 1) moieties appear upon oxidation of the σ-bonded ferrocene-ethynyl groups. These bands undergo a (stepwise) blue shift as ferrocene-ethynyl substituents on the phosphine coligands are oxidized

Fulvalene-bridged Heterobimetallic Complexes from Sandwich and Half-.Sandwich Compounds with Early-Late Transition Metals

A straightforward synthesis methodology for the preparation of heterobimetallic [(η5-C5H5)(η5-C5H4-C5Me4)M] (3a, M = Fe; 3b, M = Ru) and [(η5-C5H5)((μ-η5:η5-C5H4-C5Me4)TiCl3)M] (4a, M = Fe; 4b, M = Ru) in which early and late transition metals are connected by a fulvalenediyl bridge is reported.The structures of molecules 3b and 4a in the solid state are discussed. Most noteworthy in 4a is the exo arrangement of the iron and titanium atoms coordinated by the fulvalenediyl unit which itself is twisted with a dihedral angle between the joined cyclopentadienyl rings of 19.33(9)°. Electrochemical, UV/Vis/NIR spectroscopic and spectroelectrochemical experiments on 4a and Cp*TiCl3, for comparison, provide evidence for some transfer of electronic information between the conjoined ferrocene and half-sandwich titanocene trichloride subunits of 4a. Evidence comes from systematic potential shifts and the presence of a fairly intense Fe → Ti charge-transfer absorption band that vanishes upon oxidation and reduction of 4a

Dual Fluorescence and Phosphorescence Emissions from Dye-Modified (NCN)-Bismuth Pincer Thiolate Complexes

We report the synthesis, characterization, and photophysical properties of four new dye-modified (NCN)Bi pincer complexes with two mercaptocoumarin or mercaptopyrene ligands. Their photophysical properties were probed by UV/vis spectroscopy, photoluminescence (PL) studies, and time-dependent density functional theory (TD-DFT) calculations. Absorption spectra of the complexes are dominated by mixed pyrene or coumarin π → π*/n(pS) → pyrene or coumarin π* transitions. While unstable toward reductive elimination of the corresponding disulfide under irradiation at room temperature, the complexes provide stable emissions at 77 K. Under these conditions, coumarin complexes 2 and 4 exhibit exclusively green phosphorescence at 508 nm. In contrast, the emissive properties of pyrene complexes 1 and 3 depend on the excitation wavelength and on sample concentration. Irradiation into the lowest-energy absorption band exclusively triggers red phosphorescence from the pyrenyl residues at 640 nm. At concentrations c < 1 μM, excitation into higher excited electronic states results in blue pyrene fluorescence. With increasing c (1–100 μM), the emission profile changes to dual fluorescence and phosphorescence emission, with a steady increase of the phosphorescence intensity, until at c ≥ 1 mM only red phosphorescence ensues. Progressive red-shifts and broadening of steady-state excitation spectra with increasing sample concentration suggest the presence of static excimers, as we observe it for concentrated solutions of pyrene. Crystalline and powdered samples of 1 indeed show intermolecular association through π-stacking. TD-DFT calculations on model dimers and a tetramer of 1 support the idea of aggregation-induced intersystem crossing (AI-ISC) as the underlying reason for this behavior.publishe

Ruthenium Complexes with Vinyl, Styryl, and Vinylpyrenyl Ligands: A Case of Non-Innocence in Organometallic Chemistry

We herein describe a systematic account of mononuclear ruthenium vinyl complexes L−{Ru}−CHCH−R where the phosphine ligands at the (PR‘3)2Ru(CO)Cl{Ru} moiety, the coordination number at the metal (L = 4-ethylisonicotinate or a vacant coordination site) and the substituent R (R = nbutyl, phenyl, 1-pyrenyl) have been varied. Structures of the enynyl complex Ru(CO)Cl(PPh3)2(η1:η2-nBuHCCHCCnBu), which results from the coupling of the hexenyl ligand of complex 1a with another molecule of 1-hexyne, of the hexenyl complexes (nBuCHCH)Ru(CO)Cl(PiPr3)2 (1c) and (nBuCHCH)Ru(CO)Cl(PPh3)2(NC5H4COOEt-4) (1b), and of the pyrenyl complexes (1-Pyr-CHCH)Ru(CO)Cl(PiPr3)2 (3c) and (1-Pyr-CHCH)Ru(CO)Cl(PPh3)3 (3a-P) have been established by X-ray crystallography. All vinyl complexes undergo a one-electron oxidation at fairly low potentials and a second oxidation at more positive potentials. Anodic half-wave or peak potentials show a progressive shift to lower values as π-conjugation within the vinyl ligand increases. Carbonyl band shifts of the metal-bonded CO ligand upon monooxidation are significantly smaller than is expected of a metal-centered oxidation process and are further diminished as the vinyl CHCH entity is incorporated into a more extended π-system. ESR spectra of the electrogenerated radical cations display negligible g-value anisotropies and small deviations of the average g-value from that of the free electron. The vinyl ligands thus strongly contribute to or even dominate the anodic oxidation processes. This renders them a class of truly “non-innocent” ligands in organometallic ruthenium chemistry. Experimental findings are fully supported by quantum chemical calculations: The contribution of the vinyl ligand to the HOMO increases from 46% (Ru-vinyl delocalized) to 84% (vinyl dominated) as R changes from nbutyl to 1-pyrenyl