Sergejus Balciunas

Vilnius University · Institute of Applied Electrodynamics and Telecommunications

Polydimethylsiloxane (PDMS)-based composites filled with 80, 300, and 700 nm-sized BaTiO3 (BTO) particles at different concentrations (23, 30, and 40 vol %) were prepared, and their temperature and frequency dielectric properties, as well as electromechanical energy harvesting performance, were studied. BTO/PDMS composites exhibit a low-temperature...

The polarity of the polymer surface charge is important for constructing triboelectric devices where asymmetric charging tendencies of contacting materials are required. In the present work, we show that the addition of UiO-66 and UiO-66-NH2 metal–organic framework (MOF) particles into a polyether block amide (PEBA) polymer increases the triboelect...

Recently, hybrid double-perovskite structures have attracted attention due to their versatile multifunctional properties originating from the variety of different constituent units in these materials. Here, we report the synthesis and comprehensive multitechnique characterization of a novel hybrid double-perovskite formate-based material [CH3CH2NH3...

Hybrid organic–inorganic lead halide perovskites are promising candidates for next-generation solar cells, light-emitting diodes, photodetectors, and lasers. The structural, dynamic, and phase-transition properties play a key role in the performance of these materials. In this work, we use a multitechnique experimental (thermal, X-ray diffraction,...

Ferrites are usually used in accelerators for tuning radiofrequency (RF) cavities and in nonreciprocal devices controlling the power flow in RF accelerating systems. The conventional parallel‐biased Ni Zn ferrites employed for varying the frequency of accelerating cavities have the disadvantage of high saturation magnetization (4πMs). Application o...

Mixing molecular cations in hybrid lead halide perovskites is a highly effective approach to enhance the stability and performance of optoelectronic devices based on these compounds. In this work, we prepare and study novel mixed 3D methylammonium (MA)-ethylammonium (EA) MA1-x EA x PbI3 (x < 0.4) hybrid perovskites. We use a suite of different tech...

Na2FeP2O7 is a cathode material for sodium-ion batteries, distinguished from many other types of cathodes by its superb cycling stability. However, its electrical conductivity has not been characterized. Moreover, the electrode kinetics in sodium-ion batteries in general are poorly understood. Both are crucial for further optimization of battery ma...

Mixing of molecular cations in hybrid lead halide perovskites is a highly effective approach to enhance stability and performance of the optoelectronic devices based on these compounds. In this work, we prepare and study novel mixed methylammonium (MA)-ethylammonium (EA) MA1-xEAxPbI3 (x < 0.4) hybrid perovskites. We use a suite of different techniq...

A proper understanding of structural phase transitions and cation dynamics in hybrid lead halide perovskites is important for further enhancement of the photovoltaic properties of these materials. Here, we propose a model describing the FA cation ordering in FAPbX3 (X = Br, I) hybrid perovskites. Our model is based on the available structural infor...

The 1H-13C cross-polarization (CP) kinetics in poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) was studied under moderate (10 kHz) magic-angle spinning (MAS). To elucidate the role of adsorbed water in spin diffusion and proton conductivity, PMETAC was degassed under vacuum. The CP MAS results were processed by applying the anisot...

The organic components in metal-organic frameworks (MOFs) are unique: they are embedded in a crystalline lattice, yet, as they are separated from each other by tunable free space, a large variety of dynamic behavior can emerge. These rotational dynamics of the organic linkers are especially important due to their influence over properties such as g...

p>We use a multi-technique approach to determine the phase diagram and molecular cation dynamics of mixed methylammonium-formamidinium MA1-xFAxPbBr3 (0 ≤ x ≤ 1) hybrid perovskites. The calorimetric, ultrasonic and X-ray diffraction experiments show a substantial suppression of the structural phase transitions and stabilization of the cubic phase up...

(Cu1-xAgx)7GeS5I solid solutions in the form of single crystals have been investigated by impedance spectroscopy in the temperature range from 110 K to 350 K. The partial substitution of mobile Cu⁺ and Ag⁺ ions affects the conductivity of these compounds, which is explained by mixed-ion effect.

In this contribution, more evidence is provided to support the presence of low-temperature anomaly in CsPbBr 3 single crystals.

Broadband dielectric spectroscopy was used to study potassium niobate (KN) and barium titanate (BT) core– shell-like composites. KN shell was obtained using a solvothermal reaction method. High frequency results show a huge anomaly that is associated with electro-mechanical coupling. We tried to extract spontaneous polarization values using a theor...

Cation engineering provides a route to control the structure and properties of hybrid halide perovskites, which has resulted in the highest performance solar cells based on mixtures of Cs, methylammonium, and formamidinium. Here, we present a multi-technique experimental and theoretical study of structural phase transitions, structural phases and d...

The organic components in metal-organic frameworks (MOFs) enjoy a unique situation: they are embedded in a crystalline lattice, yet, as they are separated from each other by tunable free space, a large variety of dynamic behavior can emerge. These rotational dynamics of the organic linkers are especially important due to their influence over proper...

Cesium–lead–bromide (CsPbBr3) is the simplest all inorganic halide perovskite. It serves as a reference material for understanding the exceptional solar cell properties of the organic–inorganic hybrid halide perovskites and is itself discussed as an alternative absorber material. Broadband dielectric spectroscopy has proven to yield an in depth und...

We present a dielectric spectroscopy study of dipolar dynamics in the hydrated UiO-66(Zr) type metal-organic frameworks (MOFs) functionalized with −NH2 and −F groups. Experiments are performed in a broad temperature and frequency ranges allowing us to probe several dipolar relaxations. For both samples at temperature below 220 K, we observe confine...

Formation of noncentrosymmetric three-dimensional (3D) lead halide perovskites has been a widely sought after goal since polar structure opens up new vistas to properties of these materials, e.g. improved charge separation for photovoltaics arising from ferroelectric order. Here, we report growth and unique properties of a new highly distorted 3D p...

The 1H–13C cross-polarization magic angle spinning (CP MAS) kinetics was studied in poly(vinyl phosphonic acid) (pVPA), i.e. material with high degrees of freedom of proton motion along H-bonded chains. It has been shown that the CP kinetic data for the adjacent 1H–13C spin pairs can be described in the frame of the isotropic spin-diffusion approac...

We report the synthesis and dielectric characterization of novel polyvinylidene fluoride-trifluoroethylene P(VDF-TrFE) composite films containing [(CH3)2NH2][Mg(HCOO)3] (DMAMg) and [NH4][Zn(HCOO)3] (AmZn) dense metal-organic frameworks (MOFs). The optical camera and Raman microscopies are used to map the distribution of the MOF fillers in the prepa...

The indications of peculiar multiferroic behavior of dimethylammonium metal-formate perovskite frameworks raised important questions about the origin of the structural phase transition, structural phases and dipolar dynamics in these compounds. Here we provide answers on some of these phenomena by presenting a comprehensive experimental and theoret...

We present a combined study of [(CH3)2NH2][Cd(N3)3] hybrid perovskite dense metal-organic framework by IR, Raman, continuous-wave electron paramagnetic resonance (CW EPR), phase-transition-induced current and dielectric measurements. The Raman and IR study has shown that the phase transition observed near 175 K is associated with a pronounced narro...

Remarkable gas adsorption properties of zeolitic imidazolate frameworks (ZIFs) are believed to be tightly related to a flexible nature of organic linkers in these compounds. We present a low-frequency dielectric spectroscopy study of dynamic effects in ZIF-90 hybrid compound. Experiments of dehydrated framework reveal slow motion of imidazolate-2-c...

Here we report the dynamics of organic cations as guest molecules in a perovskite host-framework. The molecular motion of CH3NH3+ (MAFe), (CH3)2NH2+ (DMAFe) and (CH3)3NH+ (TrMAFe) in the cage formed by KFe(CN)63- units was studied using combination of experimental methods: (i) thermal analysis, (ii) dielectric and electric studies, (iii) optical ob...

Dielectric properties of 2,3,6,7,10,11-hexahydroxytriphenylene tetrahydrate crystallites are examined in this paper. We observe a first order, order-disorder phase transition at a temperature of 251 K. The frequency dependence revealed four relaxation regions, where two relaxations follow the Arrhenius law with activation energy of 300 meV. Our inv...

This paper presents dielectric properties of BT-BT and BT-BF composites obtained by solvothermal solidification. We observe lower dielectric permittivity in BT-BT composites than in conventional sintered BT ceramics. The frequency dependence showed two relaxation regions that occur due to domain wall motion and acoustic resonance. Also we observed...

Metal–organic frameworks (MOFs), in which framework is formed of metal centers coupled by organic molecules, exhibit inherent porosity and crystallinity. Although these systems have been examined for vast potential applications, the multiferroic properties in MOFs still remain poorly understood. One of the approaches to get insight into the ferroic...

The broadband dielectric properties of high sensitivity piezoelectric 0.36BiScO3-0.64PbTiO3 ceramics with average grain sizes from 1.6 μm down to 26 nm were investigated in the 100–500 K temperature range. The grain size dependence of the dielectric permittivity was analysed within the effective medium approximation. It was found that the generalis...

Charge carriers in methylammonium lead perovskite solar cell absorbers assume a combined (hyper-) polaronic state combining a classical Fröhlich polaron with a micelle-like arrangement of electric dipoles formed by the methylammonium ions. This “micellion” provides an extra contribution to the dielectric constant which screens defects but maintains...

The high power conversion efficiency of the hybrid CH3NH3PbX3 (where X = I, Br, Cl) solar cells is believed to be tightly related to the dynamics and arrangement of the methylammonium cations. In this Letter, we propose a statistical phase transition model which accurately describes the ordering of the CH3NH3⁺ cations and the whole phase transition...

We present a continuous wave electron paramagnetic resonance (EPR) study of Mn²⁺ doped [(CH3)2NH2][Zn(HCOO)3] hybrid dense metal-organic framework (MOF) that exhibits an order-disorder structural phase transition at Tc = 163 K. The W-band EPR measurements of powder sample are performed to verify the previously reported spin Hamiltonian parameters o...

Due to the unprecedented rapid increase of their power conversion efficiency, hybrid organic–inorganic perovskites CH3NH3PbX3 (X = I, Br, Cl) can potentially revolutionize the world of solar cells. However, despite tremendous research activity, the origin of the exceptionally large diffusion length of their photogenerated charge carriers, that is,...

This paper is focused on dielectric properties of potassium niobate (KN) –barium titanate (BT) composites with artificial morphotropic phase boundary (MPB). Ceramics with highest concentration of KN showed a glassy behaviour below 300 K temperature. Also two relaxation processes were observed, one in MHz and second at GHz range. The relaxation proc...

We present a combined continuous-wave (CW) and pulse electron paramagnetic resonance (EPR), pulse electron-nuclear double resonance (ENDOR), pyrocurrent as well as broadband dielectric study of [CH3NH2NH2][Zn(HCOO)3] dense perovskite metal-organic framework (MOF). The pyroelectric current of a single crystal sample reveals two structural phase tran...

We report temperature-dependent electric, IR and Raman studies of niccolite-type formate frameworks templated by protonated 1,4-diaminobutane. Our results show that the zinc-analogue exhibits a first-order phase transition close to 240 K. Single-crystal dielectric data show a much stronger anomaly at the phase transition for e′ along the a-directio...

We propose a combined experimental and numerical study to describe an order-disorder structural phase transition in perovskite-based [(CH3)2NH2][M(HCOO)3] (M = Zn(2+), Mn(2+), Fe(2+), Co(2+) and Ni(2+)) dense metal-organic frameworks (MOFs). The three-fold degenerate orientation of the molecular (CH3)2NH2(+) (DMA(+)) cation implies a selection of t...

The dielectric properties of high-temperature piezoelectric 0.36BiScO3–0.64PbTiO3 ceramics located at the morphotropic phase boundary with decreasing average grain sizes from 1.6 μm down to 26 nm were investigated in the 100–500 K temperature range and 100 Hz–40 GHz frequency region. Analysis of the current data and comparison with results of Porok...

Synthesis, crystal structure, vibrational and dielectric properties of [C7H18N2]2ClBiCl6.H2O are reported. The compound crystallizes at room temperature in the orthorhombic system, space group P212121, with the following unit cell parameters : a = 7.5500(6) Å, b = 18.3780(2) Å, c = 19.8980(13) Å, V = 2760.9(4) Å3 and four molecules per unit cell. T...