Michael Roth

Hebrew University of Jerusalem | HUJI · Department of Applied Physics

9/65/35 PLZT relaxor was studied under a bias electric field using the acoustic emission method. It was established that the temperature of smeared dielectric constant maximum exhibits the V-shape, lying fully within the ergodic phase, as well as that the threshold electric field is found to be approximately the same as in both PMN-0.24PT and PFN-0...

(1-x)PbMg1/3Nb2/3O3-xPbTiO3, [100]-oriented relaxor ferroelectric crystals were studied by means of dielectric and acoustic emission methods in dependence on temperature and under ac measuring electric field with several values and frequencies. The dependence of temperature of dielectric constant maximum on and without ac field value and frequency...

( )PbMg Nb O PbTiO 3 , [100]-oriented relaxor ferroelectric crystals were studied by means of dielectric and acoustic emission methods in a temperature range up to 200 °C and under a dc bias electric field up to 1.2 kV/cm. The monoclinic-tetragonal and tetragonal-cubic ferroelectric phase transitions were successfully detected by both experimental...

In relaxor (1- x )SrTiO 3 - x BiFeO 3 ferroelectrics ceramics ( x = 0.2, 0.3 and 0.4) both intermediate temperatures and Burns temperatures were successfully detected and their behavior were investigated in dependence on an external bias field using an acoustic emission. All these temperatures exhibit a non-trivial behavior, i.e. attain the minima...

EPL, 129 (2020) 67002 Please visit the website www.epljournal.org Note that the author(s) has the following rights:-immediately after publication, to use all or part of the article without revision or modification, including the EPLA-formatted version, for personal compilations and use only;-no sooner than 12 months from the date of first publicati...

Na0.5Bi0.5TiO3-xBaTiO3 ceramics samples (0< x < 0.8) were studied by means of an acoustic emission method. The characteristic temperatures such as the Burns temperature, T B, the transition to paraelectric phase, T p, the temperature maximum of the dielectric constant, T m, and the intermediate temperature, were detected and their dependences on x...

A low cost time domain system for measuring dielectric relaxation in the frequency range of 1 Hz - 1 MHz of solid and molten material at high temperatures is described in detail. A parallel plate electrode sample cell is described that can hold molten material by capillary action. In order to avoid electrical breakdown or a change in electrode dist...

Na(Formula presented.)Bi(Formula presented.)TiO3–0.06BaTiO3 relaxor ferroelectrics ceramics samples, doped with 1(Formula presented.)wt.% of CuO, Fe2O3, Sb2O3, La2O3 and Ta2O5, were investigated. The grain structures were observed and corresponding piezomodulus (Formula presented.) were measured for all the compounds at room temperature. It was sho...

Na0.5Bi0.5TiO3-xBaTiO3 (0<x<6) relaxor ferroelectrics crystals were investigated by means of dielectric and acoustic emission methods. Dielectric curves exhibit the slightly visible small maxima near the depolarization temperatures, Td, and the wide maxima at the temperatures of Tm, whereas the acoustic emission exhibits the sharp bursts, correspon...

[001] lead free relaxor ferroelectrics crystals of Na0.5Bi0.5TiO3–0.06BaTiO3 were studied by means of dielectric and acoustic emission methods in the temperature range of 25–240 °C and under a dc bias electric field up to 0.4 kV/cm. A temperature maximum of the dielectric constant was found near 170 °C, as well as the acoustic emission bursts point...

Na0.5Bi0.5TiO3-xBaTiO3 (0<x<6) relaxor ferroelectrics crystals were investigated by means of dielectric and acoustic emission methods. Dielectric curves exhibit the slightly visible small maxima near the depolarization temperatures, T-d, and the wide maxima at the temperatures of T-m, whereas the acoustic emission exhibits the sharp bursts, corresp...

Na(Formula presented.)Bi(Formula presented.)TiO3-0.06BaTiO3 relaxor ferroelectrics (RFEs) ceramic samples were investigated by means of dielectric and acoustic emission methods in the temperature range of 70–350(Formula presented.)C and in dependence on frequency. Dielectric curve exhibits two anomalies: strongly dispersive the local maximum, withi...

Canonical relaxor ferroelectric Pb(Mg1/3Ta2/3)O3 single crystals were studied via acoustic emission in temperature range of 180–250 K covering their dielectric constant temperature maximum at Tm ≈ 202 K, and under dc external electric fields up to 1.2 kV cm−1. The dependence of Tm on dc external electric field exhibits a nonlinear behavior, charact...

Pb(Fe0.5Ta0.5)O3 magnetic and ferroelectric relaxor multiferroic crystals have been studied under both temperature and dc external electric field conditions by means of acoustic emission technique. All the characteristic relaxor points as Burns Td≈610K and intermediate T*≈500K temperatures, as well as both Curie ferroelectric cubic-tetragonal Tc1≈2...

Ferroelectric PbSc0.5Ta0.5O3 crystals with high degree of chemical B-site order and relaxor PbSc0.5Ta0.5O3 crystals with low degree of chemical B-site order were studied by acoustic emission near their intermediate characteristic temperature &$T^*$ ;. The acoustic emission data were subjected to fast Fourier transform procedure. It was established...

BaxSr1–xTiO3 ferroelectrics ceramic with x = 70 and 80% have been studied by means of acoustic emission over a wide 0–300 °C temperature range and under dc external electric field. All the Curie temperatures Tc, intermediate temperatures T*, and Burns temperatures Td have been successfully detected and compared with those previously detected in Bax...

Acoustic emission (AE) spectroscopy without frequency filtering (∼broadband AE) and moderate time integration is shown to be sensitive enough to allow the investigation of subtle nano-structural changes in ferroelectric BaTiO3 and ferroelastic Pb 3(PO4)2. AE signals during weak phase transitions are compatible with avalanche statistics as observed...

Lead-based ABO3-type relaxors and related systems have numerous applications in modern technical devices because of their remarkably high dielectric permittivity and piezoelectric/electroelastic and electro-optic coefficients. However, lead is not desired from an environmental point of view, and to switch to alternative alkali-, Ba-, or Bi-based re...

BaTiO3 crystals, grown by Remeika method, were studied by means of acoustic emission and dielectric response. It is established, that the phase transition in the surface layer occurs on 13 degrees C below in comparing with the crystals bulk. It is observed, that the imaginary dielectric response of a crystal surface layer exhibits an essential smea...

Highly ordered ferroelectric PbSc0.5 Ta 0.5O3 crystals were studied by acoustic emission over a wide temperature range. Acoustic emission was found at three characteristic temperatures: 330, 409, and ≈600 K, which are close to those, known from the same disordered crystals, containing polar nanoregions. The microstructure in our crystals contains s...

Single phase polycrystalline hexagonal boron nitride (ON) or mixed with boron carbide (B,C) embedded in an insulating polymeric matrix acting as a binder and forming a composite material as well as pure submicron size polycrystalline BN has been tested as a thermal neutron converter in a multilayer thermal neutron detector design. Metal sheet elect...

PbSc0.5Ta0.36Nb0.14O3 relaxor-ferroelectric crystals were studied by the means of dielectric and acoustic emission (AE) methods in the temperature range of 180–300 K. In zero dc electric field (E) no AE was detected at the smeared dielectric maximum Tm ≈ 260 K characteristic for canonical relaxor ferroelectrics. Under the E a phase transition appea...

Ba0.60Sr0.40TiO3 ceramic ferroelectric (FE) has been investigated in the wide temperature range under a dc external electric field (E) by means of dedicated acoustic emission (AE) method. The Curie point Tc = 9 °C, as well as both the temperature points, characteristic of relaxor ferroelectrics (RFEs), Burns temperature Td = 283 °C and intermediate...

PbSc0.5Ta0.36Nb0.14O3 relaxor ferroelectrics crystals were investigated in a wide temperature range of 200–700 K using acoustic emission. The intermediate temperature T* as well as the Burns temperature Td were successfully detected at 480 K and 581 K, respectively. Another acoustic emission burst was detected at Tnl ∼ 211 K, which is below the tem...

PbFe1/2Nb1/2O3 ferroelectrics crystals have been investigated using an acoustic emission. All the characteristic points have been detected: the Néel antiferromagnetic-paramagnetic phase transition at 158.6 K, both the rhombohedral-tetragonal at 363-348 K and tetragonal-cubic at 382-365 K structural phase transitions, the intermediate temperature T...

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Abstract—The temperature dependences of the pyroelectric coefficients of KTiOAsO4 and RbTiOAsO4 sin� gle crystals grown by flux crystallization have been investigated in the temperature range of 4.2–300 K. With an increase in temperature, superionic conductivity first arises in KTiOAsO4 (at T > 200 K) and then (at T > 270 K) in RbTiOAsO4. This cond...

Cubic-tetragonal phase transitions of [100]-oriented BaTiO3 crystals have been studied by means of an acoustic emission (AE) method, under an external electric field. The Curie temperature (Tc) reveals a nontrivial behavior at the small field, namely, it initially decreases with enhancement of the field, attains a minimum at the threshold field Eth...

The behavior of the temperature of the dielectric-permittivity maximum Tm, the intermediate temperature T*, and the Burns temperature Td in stoichiometric PbSc0.5Nb0.5O3 (PSN) as well as in PSN heavily doped on the A-site by La (PSN-La), Ba (PSN-Ba), and Sr (PSN-Sr) was studied by means of acoustic emission (AE) under an external dc electric field...

We measured the terahertz (THz) complex conductivity of Ca-doped YBa2Cu3O7-delta thin films in the frequency range of 0.1 to 3THz (3 to 100 cm(-1)) and in the temperature range of 20 to 300 K. The films were measured using time domain and frequency domain THz spectroscopy methods. We show evidences for the existence of an additional energy sub-gap...

A low-voltage (mV) electronically triggered spot welding system for fabricating fine thermocouples and thin sheets used in high-temperature characterization of materials' properties is suggested. The system is based on the capacitance discharge method with a timed trigger for obtaining reliable and consistent welds. In contrast to existing techniqu...

We measured the terahertz (THz) complex conductivity of Ca doped YBa_{2}Cu_{3}O_{7-\delta} thin films in the frequency range of 0.1 to 3 THz (3 to 100 cm^{-1}) and at a temperature range of 20 to 300 K. The films were measured using both time domain and frequency domain THz methods. We showed evidence for the existence of a sub-gap in overdoped Y_{...

Sr0.75Ba0.25Nb2O6 [100]-oriented uniaxial tungsten bronze relaxor crystals have been studied by means of dedicated acoustic emission during their thermal cycling in 150–300 K temperature range under dc electric field (E). A 1st order transition in a modulated incommensurate tetragonal phase has been successfully detected at Tmi = 198 K on heating a...

[100]-oriented KTa1−xNbxO3 (x=0.32) relaxor ferroelectric crystals have been studied by acoustic emission (AE) count rate Ṅ in the temperature range from 200 K to 700 K. Burns temperature Td=620 K (Ṅ = 1.7 −1) and intermediate temperature T*=310 K (Ṅ = 3.1 −1) as well as both the tetragonal-cubic TT-C=259 K (Ṅ = 4.0 −1) and orthorhombic-tetragonal...

The acoustic emission (AE) method is presented as a useful complementary tool for nondestructive characterization of selective relaxor ferroelectrics. Combined measurements of the dielectric permittivity and AE activity as a function of temperature and externally applied electric fields have been carried out using Pb(Mg1/3Nb2/3)O3–33%PbTiO3 (PMN-0....

[100] oriented Sr0.75Ba0.25Nb2O6 relaxor crystals have been studied by means of acoustic emission (AE) over a wide 20–400 °C temperature range. Both the Burns temperature, Td = 350 °C, and the intermediate temperature, T* = 183°C, and the susceptibility maximum temperature, Tm (59 °C on heating and 47 °C on cooling), have been successfully detected...

Two model relaxor ferroelectrics PbSc0.5Ta0.5O3 (undergoing a spontaneous para-to-ferroelectric phase transformation) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (no long-range ferroelectric order in the absence of an external electric field) were studied by acoustic emission in the temperature range 200–600 K under a dc field E. Both compounds exhibit a para-to-...

We measured the complex conductivity of Ca-doped YBCO thin films in the THz frequency range. The films were measured using both Time domain and Frequency domain methods for THz spectroscopy. We show that a subgap exists in the overdoped samples of 5% and 10% Ca doping. The subgap appears as a sharp decrease in the real part of conductivity at frequ...

The domain morphology and crystal structure of (1-x)( Bi _1/2 Na _1/2) TiO ₃x BaTiO ₃ lead-free piezoelectric ceramics were systematically studied with transmission electron microscopy for compositions x=0.04 through 0.11. It was found that the ceramics with compositions x<0.06 display a R3c symmetry with...

Chemically B-site disordered PbScl/2Tal/2O3 relaxor crystals have been studied by means of dielectric and acoustic emission methods in the vicinity of Tm≈280 K. Along with the intrinsic cubic-to-rhombohedral phase transformation at Tc=261 K, a phase transformation at Tn=293 K is evidently detected by acoustic emission. Under an external dc electric...

Thin layers of composite material, natural boron and boron carbide (B(4)C) with natural abundance of (10)B, mixed with binder were used as thermal neutron convertors in a multilayer thermal neutron detector design. Plane metal electrodes of 4 -100 cm(2) area were covered with thin (20-50 mu m thick) layers of converter material and assembled in a 4...

BaTiO3 crystals were studied by means of the acoustic emission during thermal cycling through 300–700 K range. In addition to pronounced acoustic emission at the ferroelectric phase transition temperature Tc ≈ 400 K, also nucleation of nanoclusters was detected at somewhat smeared Burns temperature Td ≈ 530–570 K and their local freezing at T∗ ≈ 50...

Oriented {100}-, {110}-, and {111}-cuts of Pb₀.₇₈)Ba₀.₂₂Sc₀.₅Ta₀.₅O₃ single crystals have been studied by means of the acoustic emission (AE) method during their thermal cycling in the temperature range of 300-600 K. For all crystal orientations pronounced AE signals have been detected near 490 K, which corresponds to the intermediate temperature T...

The unit cell parameters of KTiOPO4 and KTiOAsO4 single crystals are measured in the temperature range from room temperature to 20 K. It is found that the unit cell volume of the single crystals changes smoothly. With a decrease in temperature, the c parameter remains almost unchanged. In a certain temperature range, the linear temperature dependen...

Growth of large and optically uniform single crystals of KTiOPO4 (KTP) and its isomorphs is of great importance in laser frequency conversion applications. We have demonstrated that the size of the crystal must not be sacrificed in the quest for attaining high quality. The top-seeded solution growth from pure and modified self-fluxes with pulling o...

Potassium titanyl phosphate (KTP) single crystals have been grown by the top-seeded pulling (in Z-direction) from modified fluxes. The fluxes contained a mixture of two solvents, the conventional K6P4O13 phosphate and excessive amounts of PbO, 70–80 wt% relatively to the phosphate. Crystals with a single domain (001) growth sector core have been ob...

The temperature dependence of the pyroelectric coefficient, γs, of RbTiOAsO4 single crystals grown by seeded pulling from high-temperature self-fluxes has been studied in the low-temperature range. The results show that in the 4.2–250 K temperature range the γs(T) behavior is similar to those of the isomorphic crystals belonging to the KTP (KTiOPO4...

In the current work we have investigated the terahertz response of Ca overdoped YBaCuO thin films using both time and frequency domain spectroscopy methods. For both methods a basic data analysis was performed using the two fluid and a variable dielectric function (VDF) models. The imaginary part of the conductivity was proportional to 1/ω, known f...

We have carried out a combined acoustic emission (AE) and dielectric permittivity study of the x Pb ( Zr _1/2 Ti _1/2) O ₃-(1-x) Pb ( Ni _1/3 Nb _2/3) O ₃ relaxor ferroelectric ceramics with compositions x=0.7–0.9 corresponding to its morphotropic phase boundary. Temperatures of all phas...

In recent years the growth technologies of only afew inorganic oxide crystals, such as BBO (BaB2O4), LBO (LiB3O5), and the KTP (KTiOPO4) group of isomorphic compounds, have matured to adegree allowing their extensive integration into commercial laser systems in the form of nonlinear optical (NLO) and electrooptic (EO) devices. The KTP-t...

Via a combination of various experimental and theoretical techniques, a peculiar, identical temperature scale T∗ is found to exist in all complex lead-based relaxor ferroelectrics studied by us. T∗ corresponds to a nanoscale phase transition associated with random fields. Interestingly, T∗ also exists in other oxides with extraordinary properties,...

Single phase polycrystalline hexagonal boron nitride (BN) or mixed with boron carbide (BxC) and/or polycrystalline cubic lithium fluoride (LiF) can be embedded in an insulating polymeric matrix. This matrix acts as a binder forming a composite material. Such materials were tested as surface neutron converters of gaseous detectors. Signals were indu...

A modification of the Angsrom's temperature wave method for measuring the thermal properties of materials has been employed for in situ experimental evaluation of thermal diffusivities of high-temperature solutions. High-temperature solutions used for the growth nonlinear optical BBO (BaB2O4) and KTiOPO4 (KTP) crystals have been studied, namely BBO...

We discuss the nature of the thermally stimulated acoustic emission (AE) in single crystals of PbMg1/3Nb2/3O3–PbTiO3 (PMN-PT). In particular, we derive an expression describing the efficiency of AE and we discuss in this connection AE from pure PMN. We have carried out original experiments revealing the dependence of AE in PMN-PT on the electric bi...

The ferroelectric strain hysteresis and acoustic emissions of lead-free (1 − x − y)Bi0.5Na0.5TiO3–xBaTiO3–yK0.5Na0.5NbO3 ceramics were investigated at room temperature. The field-induced antiferroelectric ↔ ferroelectric phase transition as well as the ferroelectric coercive field were successfully detected. Although the strain was largest for x =...

Via a combination of various experimental and theoretical techniques, a peculiar, identical temperature scale T* is found to exist in all complex lead-based relaxor ferroelectrics. T* corresponds to a nanoscale phase transition due to random fields. Interestingly, T* also exists in other oxides with extraordinary properties, such as giant magnetore...

This paper reports on the results of precision X-ray structural investigations of KTiOPO4 single crystals grown by one method (crystallization from a solution in the melt) in two variants (the spontaneous formation of crystallization centers or top-seeded solution growth during slow cooling of saturated solution melts). It is shown that spontaneous...

The pyroelectric properties of samples cut from various growth sectors of RbTiOPO4 single crystals grown from solution in a melt were measured in the temperature range from 4.2 to 300 K. The experimental values of the pyroelectric coefficient range from −1.3 × 10−5 to −4.6 × 10−5 C/m2 K. For the samples cut from the (100) sector, pronounced anomali...

We investigated the ceramics samples of multiferoic solid solution of relaxor ferroelectric Pb ( Fe _2/3 W _1/3) O ₃ with ferroelectric Pb Ti O ₃ (abbreviated as PFW -x PT ; x=0 , 0.25, and 0.37) by means of acoustic emission (AE) method and simultaneously using the dielectric measurement below 700 K . A di...

RbTiOPO4 crystals have been grown by the top-seeded solution method from self-fluxes containing [Rb]/[P] molar ratios as high as 2.3 and initial solute concentrations of 1.2g-RTP/g-flux, corresponding to the previously unexplored part of the RTP crystallization field in the Rb2O–P2O5–TiO2 ternary system. The Curie temperatures of as-grown crystals...

Magnetization hysteresis loops of Cu/MgB2, Nb/MgB2, Cu/Nb/MgB2 and Fe/Cu/MgB2 wires in parallel magnetic fields of up to 5 T were studied in the temperature range from 5 to 35 K. All Nb-clad samples exhibited a thermomagnetic instability (TMI) in the form of magnetization jumps. In a thick wire (about 2 mm in core diameter), the TMI persisted up to...

Acoustic emission measurements are combined with strain, dielectric, and polarization measurements to detect phase transitions in 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 single crystals during thermal cycling as well as electric field cycling at both room temperature and 140 °C. All phase transitions known from the literature (cubic↔tetragonal↔trigonal I↔tri...

The dominant Ti3+ trapped electron center in flux-grown RbTiOPO4 (RTP) crystals has been characterized using electron paramagnetic resonance (EPR) and electron–nuclear double resonance (ENDOR). This center is produced during an X-ray irradiation at room temperature when a Ti4+ ion traps an electron and becomes a Ti3+ ion, and is best studied in the...

Pyroelectric properties of high resistivity RbTiOPO4 single crystals cut from different growth sectors ({100}, {110} and {201}) have been studied using the modified static method in a broad temperature interval, from 4.2 to 300K. A substantial scatter of the room temperature pyroelectric coefficient values has been observed, ranging from 1.3 to 4.6...

Composite polycrystalline semiconductor detectors bound with different binders, both inorganic molten glasses, such as B2O3, PbO/B2O3, Bi2O3/PbO, and organic polymeric binders, such as isotactic polypropylene (iPP), polystyrene or nylon-6, and coated with different metal electrodes were tested at room temperature for α-particles and very weak therm...

Pb(Zn(1/3)Nb(2/3))O3-xPbTiO(3) (x=4.5%-12%) relaxor ferroelectric crystals have been studied by means of acoustic emission (AE) in the 400-540 K temperature range. An anomalous AE activity independent of the ground state relaxor/morphotropic/ferroelectric crossover has been revealed at around 500 K, and it is associated with the "waterfall" feature...

Phase transitions in PbZn1/3Nb2/3O3-7%PbTiO3 (PZN-7%PT) relaxor ferroelectric crystals have been investigated by the acoustic emission (AE) method. Two types of transitions have been detected: (i) associated with the thermally induced (on cooling) formation of intrinsic polar nanoregions (PNRs) and (ii) related to the electric-field-induced macrosc...