Piezoelectric Characteristics of LiNbO3 Thin-film Heterostructures via Piezoresponse Force Microscopy

Electro-optic LiNbO3 thin films were deposited on Si(100) and Si(111) substrates using a radio-frequency magnetron sputtering process. The piezoelectric properties of the LiNbO3 films were investigated using the scanning probe microscopy in the piezoresponse mode. The obtained results show the high degree of grains orientation in polycrystalline structure. The piezoelectric modulus (dzz) was estimated to be 16 pm/V (for LiNbO3 / Si(100)) and 22 pm/V (for LiNbO3 / Si(111)) and the polarization about of 0.37 C·m – 2. These values are larger than those reported previously for LiNbO3 films. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3366

Magnetic properties of the Bi0.65La0.35Fe0.5Sc0.5O3 perovskite

Magnetic properties of polycrystalline multiferroic Bi0.65La0.35Fe0.5Sc0.5O3 synthesized under high-pressure (6 GPa) and high-temperature (1500 K) conditions were studied using a SQUID magnetometer technique. The temperature dependent static magnetic moment M was measured in both zero-field-cooled and field-cooled modes over the temperature range of 5-300 K in low magnetic field H = 0.02 kOe. The field dependent magnetization M(H) was measured in magnetic fields up to 50 kOe at different temperatures up to 230 K after zero-field cooling procedure. A long-range magnetic ordering of the antiferromagnetic type with a weak ferromagnetic contribution takes place below TN ≈ 220 K. Magnetic hysteresis loops taken below TN show a huge coercive field up to Hc ≈ 10 kOe, while the magnetic moment does not saturate up to 50 kOe. A strong effect of magnetic field on the magnetic properties of the compound has been found. Below TN ≈ 220 K the derivatives of the initial magnetization curves demonstrate the existence of a temperature-dependent anomaly in fields of H = 15÷25 kOe. The nature of the anomaly is unknown and requires additional study.publishe

Scintillator ageing of the T2K near detectors from 2010 to 2021

The T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9–2.2% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator. The long component of the attenuation length of the wavelength shifting fibres was observed to degrade by 1.3–5.4% per year, while the short component of the attenuation length did not show any conclusive degradation

Strong electrocaloric effect in lead-free 0.65Ba(Zr0.2Ti0.8)O3-0.35(Ba0.7Ca0.3)TiO3 ceramics obtained by direct measurements

International audienceStrong electrocaloric effect in lead-free 0.65Ba(Zr 0.2 Ti 0.8)O 3-0.35(Ba 0.7 Ca 0.3)TiO 3 ceramics obtained by direct measurements Solid solutions of (1 À x)Ba(Zr 0.2 Ti 0.8)O 3-x(Ba 0.7 Ca 0.3)TiO 3 promise to exhibit a large electrocaloric effect (ECE), because their Curie temperature and a multiphase coexistence region lie near room temperature. We report on direct measurements of the electrocaloric effect in bulk ceramics 0.65Ba(Zr 0.2 Ti 0.8)O 3-0.35(Ba 0.7 Ca 0.3)TiO 3 using a modified differential scanning calorimeter. The adiabatic temperature change reaches a value of DT EC ¼ 0.33 K at $65 C under an electric field of 20 kV/cm. It remains sizeable in a broad temperature interval above this temperature. Direct measurements of the ECE proved that the temperature change exceeds the indirect estimates derived from Maxwell relations by about$50%. The discrepancy is attributed to the relaxor character of this material. V C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4907774] During the last several years, an increased interest has been paid to the electrocaloric effect (ECE) in ferroelectric materials as a route to develop small, effective, low cost, and environmentally friendly solid-state refrigerators. 1,2 The ECE is defined as an adiabatic and reversible temperature change of a dielectric material when an electric field is applied or removed. 3 If the exchange of heat with the environment is enabled, it defines the change of entropy as a function of the applied electric field under isothermal conditions. 4,5 Since Mischenko et al. reported on the giant electro-caloric effect in PbZr 0.95 Ti 0.05 O 3 thin films in 2006, 6 the ECE has been reported for many different ferroelectric materials such as thick and thin films, 7–10 polymers, 11,12 bulk ceramics, 13,14 and single crystals. 15,16 In general, the ECE peaks are a few degrees above the ferroelectric-paraelectric phase transition. 1 The largest values have been achieved for thin films, 10 where much higher electric fields can be applied than to bulk materials. However, for application, the heating/ cooling capacity is the key factor. Hence, bulk materials, which have large enough heating/cooling capacity, are better suitable for mid-and large-scale cooling applications. 1 To compare the ECE in different materials, the ratio between induced temperature change and applied field, DT EC /DE, called the electrocaloric strength, has been introduced

Ferroelectric phase transitions and electroconducting properties of ceramic BIMEVOX solid solutions (Me = La, Zr)

Ceramic solid solutions Bi4(V1-xZrx)2O11-z (I), (Bi1-yLay)4V2O11-z (II) and (Bi1-yLay)4(V0.96Zr0.05)2O11-z (III) with x < 0.30, y < 0.20, were prepared by the solid state reaction method and were investigated by means of various experimental techniques. The low temperature ferroelectric α-phase exists in the solid solutions with x, y ≤ 0.05. The phase transition to paraelectric β-phase was revealed in these compositions by the dielectric spectroscopy, SHG and DTA/DSC methods. Dielectric permittivity measurements confirmed an effect of the domain walls "pinning" due to the presence of oxygen vacancies inherent to the bismuth vanadate based structures. Switching of ferroelectric domains by an external electric field was observed in Piezoresponse Force Microscopy experiments. Copyright © Taylor & Francis Group, LLC

Ferroelectric phase transitions and electroconducting properties of ceramic BIMEVOX solid solutions (Me = La, Zr)

Ceramic solid solutions Bi4(V1-xZrx)2O11-z (I), (Bi1-yLay)4V2O11-z (II) and (Bi1-yLay)4(V0.96Zr0.05)2O11-z (III) with x < 0.30, y < 0.20, were prepared by the solid state reaction method and were investigated by means of various experimental techniques. The low temperature ferroelectric α-phase exists in the solid solutions with x, y ≤ 0.05. The phase transition to paraelectric β-phase was revealed in these compositions by the dielectric spectroscopy, SHG and DTA/DSC methods. Dielectric permittivity measurements confirmed an effect of the domain walls "pinning" due to the presence of oxygen vacancies inherent to the bismuth vanadate based structures. Switching of ferroelectric domains by an external electric field was observed in Piezoresponse Force Microscopy experiments. Copyright © Taylor & Francis Group, LLC

Mono , Di , and Tri Valent Cation Doped BiFe0.95Mn0.05O3 Nanoparticles Ferroelectric Photocatalysts

The ferroelectricity of multivalent codoped Bismuth ferrite (BiFeO3; BFO) nanoparticles (NPs) is revealed and utilized for photocatalysis, exploiting their narrow electronic bandgap. The photocatalytic activity of ferroelectric photocatalysts BiFe0.95Mn0.05O3 (BFM) NPs and mono‐, di‐, or tri‐valent cations (Ag+, Ca2+, Dy3+; MDT) coincorporated BFM NPs are studied under ultrasonication and in acidic conditions. It is found that such doping enhances the photocatalytic activity of the ferroelectric NPs approximately three times. The correlation of the photocatalytic activity with structural, optical, and electrical properties of the doped NPs is established. The increase of spontaneous polarization by the mono‐ and tri‐valent doping is one of the major factors in enhancing the photocatalytic performance along with other factors such as stronger light absorption in the visible range, low recombination rate of charge carriers, and larger surface area of NPs. A‐site doping of BFO NPs by divalent elements suppresses the polarization, whereas trivalent (Dy3+) and monovalent (Ag+) cations provide an increase of polarization. The depolarization field in these single domain NPs acts as a driving force to mitigate recombination of the photoinduced charge carriers.The ferroelectricity of Ag/Ca/Dy‐doped BiFe0.95Mn0.05O3 nanoparticles are utilized for photocatalysis under ultrasonic conditions. The mitigated recombination of photoinduced charge‐carriers in the nanoparticles due to the depolarization field, is one of the important factors for the photocatalytic rate. The piezoresponse becomes a crucial parameter under ultrasonic conditions for ferroelectric photocatalysts. The pink dye (rhodamine B) is photodegraded using MDT doped nanoparticles. The ease of photoinduced charge carrier separation in single domain nanoparticles using the depolarization field as a driving force is shown. imageDeutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Peer Reviewe

Явление обменного сдвига в перовскитах (Nd₁₋хYx)₂/₃Ca₁/₃MnO₃ (x = 0; 0,1)

Обнаружен обменный сдвиг петель гистерезиса в соединениях (Nd₁₋хYx)₂/₃Ca₁/₃MnO₃ (x = 0; 0,1), возникающий при охлаждении в магнитном поле ниже температур магнитного упорядочения и свидетельствующий о магнитном фазовом расслоении этих соединений при низких температурах. Оценен вклад ферромагнитной фазы в полную намагниченность соединений. Обнаружено, что замещение неодима иттрием приводит к увеличению содержания ферромагнитной фазы в допированном соединении (Nd₀,₉Y₀,₁)₂/₃Ca₁/₃MnO₃ по сравнению с исходным соединением Nd₂/₃Ca₁/₃MnO₃. При этом ферромагнитная фаза в допированном соединении характеризуется меньшей коэрцитивной силой Hс и более прямоугольной петлей гистерезиса. Величина поля обменного сдвига HEB немонотонно зависит от магнитного поля охлаждения Нcool, и в области достаточно больших полей Нcool > 5 кЭ примерно вдвое меньше для допированного соединения. Такое различие определяется меньшей величиной обменного взаимодействия и большей величиной намагниченности насыщения ферромагнитной фазы в (Nd₀,₉Y₀,₁)₂/₃Ca₁/₃MnO₃.Виявлено обмінний зсув петель гістерезису у сполуках (Nd₁₋хYx)₂/₃Ca₁/₃MnO₃ (x = 0; 0,1), що виникає при охолодженні у магнітному полі нижче температур магнітного впорядкування та свідчить про магнітне фазове розшарування цих сполук при низьких температурах. Оцінено внесок феромагнітної фази в повну намагніченість сполук. Виявлено, що заміщення неодиму ітрієм призводить до збільшення змісту феромагнітної фази у допованій сполуці (Nd₀,₉Y₀,₁)₂/₃Ca₁/₃MnO₃ в порівнянні з базовою сполукою Nd₂/₃Ca₁/₃MnO₃. При цьому феромагнітна фаза в допованій сполуці характеризується меншою коерцитивною силою Hс та більш прямокутною петлею гістерезису. Величина поля обмінного зсуву HEB немонотонно залежить від магнітного поля охолодження Нcool, та в області досить великих полів Нcool > 5 кЕ приблизно вдвічі менше для допованої сполуки. Така різниця обумовлена меншою величиною обмінної взаємодії та більшою величиною намагніченості насичення феромагнітної фази в (Nd₀,₉Y₀,₁)₂/₃Ca₁/₃MnO₃.Exchange bias phenomenon evident of antiferromagnetic–ferromagnetic phase segregated state has been observed in (Nd₁₋хYx)₂/₃Ca₁/₃MnO₃ (x = 0; 0,1) compounds at low temperatures. A contribution to the total magnetization of the compounds due to the ferromagnetic phase has been evaluated. It has been found that yttrium doping leads to the growth of the ferromagnetic phase fraction. The ferromagnetic phase in the doped compound has a lower coercivity Hc and more rectangular form of the hysteresis loop. The values of the exchange bias field HEB and coercivity are found to be strongly dependent on the cooling magnetic field Нcool. In sufficiently high magnetic fields, Нcool > 5 kOe, the HEB value is approximately twice in the doped compound than in the parent compound. This difference is attributed to the lower exchange interaction and the higher saturation magnetization of the ferromagnetic phase in (Nd₀,₉Y₀,₁)₂/₃Ca₁/₃MnO₃