Barium titanate (BaTiO3) is a common ferroelectric material with perovskite structure widely used for the production of a variety of electro-optical devices. When doping with rare earth elements, very interesting characteristics can be attributed to BaTiO3. Among the methods used to synthesize BaTiO3, wet chemical approaches are the most suitable for preparing homogenous and pure nanostructured materials. In this sense, the present article aims to summarize the state-of-the-art of the most relevant wet chemical routes for the synthesis of nanocrystalline BaTiO3 doped with rare earth (RE) ions (BaTiO3:RE), which include the following: sol–gel, sol–emulsion–gel, Pechini, solvothermal/hydrothermal, and co-precipitation methods. The influence of each method on morphology and particle size, as well as on the dielectric and/or luminescent properties of the powders is discussed.

Wet chemical synthesis of rare earth-doped barium titanate nanoparticles

This paper studies negative bias temperature instability in commercial IRF9520 p-channel power VDMOSFETs under both static and pulsed bias stress conditions in order to model this effect. The pulsed voltage stressing caused generally lower shifts as compared to static stressing performed at the same temperature with equal stress voltage magnitude, as a consequence of partial recovery during the low level of pulsed gate voltage. It was shown that the quantitative differences between static and pulsed NBT stress depend on the duty cycle, and the differences become more significant as the duty cycle decreases. It was found that $25~\mu {\mathrm{ s}}$ off-time of the pulsed stress voltage could suffice to remove the major part of the recoverable component of the degradation created during the foregoing pulse on-time. An equivalent electrical circuit has been proposed and on the basis of these experimental results a modeling of threshold voltage shifts induced by pulsed negative bias temperature stress has been done.

Modeling of NBTS Effects in P-Channel Power VDMOSFETs

In this paper, we report an experimental evidence of the impact of applied a low magnetic field ( ${B ) during negative bias temperature instability (NBTI) stress and recovery, on commercial power double diffused MOS transistor. We show that both interface ( ${\Delta }{N_{it}}$ ) and oxide trap ( ${\Delta }{N_{ot}}$ ) induced by NBTI stress are reduced by applying the magnetic field. This reducing is more pronounced as the magnetic field is high. However, the dynamic of interface trap during stress and recovery phase is not affected by the applied magnetic field. While, the dynamic of oxide trap is affected in both stress and recovery phases.

Experimental Investigation of NBTI Degradation in Power VDMOS Transistors Under Low Magnetic Field

Influence of mechanical activation on functional properties of barium hexaferrite ceramics

La doped barium titanate/polyimide nanocomposites: A study of the effect of La doping and investigation on thermal, mechanical and high dielectric properties

This paper introduces a new experimental approach allowing to investigate the recoverable and permanent components in commercial p-channel power VDMOSFETs subjected to negative bias temperature (NBT) stressing. In many applications, devices can be used in multiple modes, which include application of static or pulsed gate voltages at different stages of device operation. Accordingly, we have investigated stress-induced degradation in the cases where the static stress was followed by the pulsed NBT stress conditions and vice versa. The results are discussed in terms of the mechanisms responsible for the buildup of oxide charge and interface traps. It has been shown that the differences in the permanent components of the oxide charge and interface traps between devices exposed to static stress followed by pulsed NBT stress and those exposed only to static NBT stress tend to decrease during the pulsed stress as the duty cycle increases but cannot be completely removed.

On the Recoverable and Permanent Components of NBTI in p-Channel Power VDMOSFETs

La/Mn codoped BaTiO 3 ceramics with different La 2 O 3 content, ranging from 0.3 to 1.0 at% La, together with undoped BaTiO 3 ,were investigated regarding their microstructure and dielectric properties. The content of MnO 2 kept constant at 0.01 at% Mn in all investigated samples. La/Mn codoped and undoped BaTiO 3 were obtained by a modified Pechini method and sintered in air at 1300 0 C for two hours. The homogeneous and completely fine-grained microstructure with average grain size from 0.3 to 1mm was observed in samples doped with 0.3 at% La. In high doped samples, apart from the fine grained matrix, the appearance of local area with secondary abnormal grains was observed. The dielectric permittivity and dissipation factor were investigated as a function of frequency and temperature. Dielectric permittivity of doped BaTiO 3 was in the range of 3945 to 12846 and decreases with increase of additive content. The highest value of dielectric constant at room temperature (e r = 12846) and the greatest change at Curie temperature (e r = 17738) were measured in 0.3at% La doped samples. Dissipation factor was range from 0.07 to 0.62 for all investigated samples. The Curie constant (C) and Curie-Weiss temperature (T 0 ) together with critical exponent of nonlinearity (g) were calculated using a Curie-Weiss and modified Curie-Weiss law. The Curie constant increase with increasing dopant content and the highest values were measured in 1.0 La doped samples.  The obtained values of g is in the range from 1.04 to 1.53 and pointed out the sharp phase transformation from ferroelectric to paraelectric phase at Curie temperature.

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DIELECTRIC PROPERTIES OF La/Mn CODOPED BARIUM TITANATE CERAMICS

This paper reports results of the transient modeling of thermoelectric cooling/heating modules as power generators with the aim to select preferable ones for use in thermal energy harvesting wireless sensor network nodes. A study is conducted using the selected commercial thermoelectric generators within the node of a compact design with aluminum PCBs. Their equivalent electro-thermal models suitable for SPICE-like simulators are presented. Model components are extracted from the geometrical, physical and thermo-electrical parameters and/or experimentally. SPICE simulation results mismatch within 7% in comparison with the experimental measurements. The presented model is used for the characterization of different thermoelectric generators within the wireless sensor network node from the aspects of harvesting efficiency, cold boot time, node dimensions and compactness, and maximum applicable temperature. The choice of the preferred generator is determined by its electrical resistance, the number of thermoelectric pairs, external area and thermoelectric legs length, depending on the primary design goal and imposed thermal operating conditions. The node can provide load power of 1.3 m W and the cold boot time of 66 s for generator with 31 thermoelectric pairs at a temperature difference of 15 ° C with respect to the ambient, and 7.6 m W of load power and the cold boot time of 40 s for generator with 71 thermoelectric pairs at a temperature difference of 25 ° C .

https://www.mdpi.com/2079-9292/9/6/1015/pdf

A Transient Modeling of the Thermoelectric Generators for Application in Wireless Sensor Network Nodes

In this study, the electrical resistivity (ρ) and PTC effect of Er doped BaTiO3 ceramics are investigated. The concentrations of Er2O3 in the doped samples vary from 0.01 to 1.0 at% Er. The samples are prepared by the conventional solid state reaction, and sintered at 1320° and 1350 °C in air atmosphere for 4 hours. The SEM analysis shows that all of measured samples are characterized by polygonal grains. The uniform and homogeneous microstructure with grain sizes from 20 to 45μm is the main characteristic of the low doped samples (0.01 and 0.1 at% Er). For the samples doped with the higher dopant concentration (0.5 and 1.0 at%) the average grains sizes have been ranged from 5 to 10 μm. The electrical resistivity is measured in the temperature range from 25 °C to 170 °C, at frequencies 1 kHz, 10 kHz and 100 kHz. The electrical resistivity values, measured at frequency of 1 kHz and room temperature, have been ranged from 1.62·104 Ωcm to 4.24∙104 Ωcm, for samples sintered at 1320 °C and from 1.43·104 Ωcm to 1.94∙104 Ωcm, for samples sintered at 1350 °C. A nearly flat and stable electrical resistivity-temperature response is characteristic for all samples at the temperature range from 25 °C to 120 °C. Above this temperature, the electrical resistivity increases rapidly. At 170°C the value of electrical resistivity is ranged 9.84·104 Ωcm -1.62·105 Ωcm, for Tsin=1320 °C, and 6.11·104 Ωcm 1.32·105 Ωcm, for Tsin=1350 °C. The electrical resistivity decreases with concentration increment up to 0.5 at%, while above 0.5 at% it increases. Also, with increasing frequency, ρ decreases for a few orders of magnitude.

/pdf/electrical-characteristics-of-er-doped-batio3-ceramics-3xqrct9ww4.pdf

Electrical characteristics of Er doped BaTiO3 ceramics

The Ho doped BaTiO3 ceramics, with different Ho2O3 content, ranging from 0.01
 to 1.0 wt % Ho, were investigated regarding their microstructural and
 dielectric characteristics. Doped BaTiO3 were prepared using conventional
 solid state reaction and sintered at 1380°C for four hours. SEM analysis of
 Ho/BaTiO3 doped ceramics showed that the low doped samples exhibit mainly
 fairly uniform and homogeneous microstructure with the grain size ranged from
 20-40 μm. In the samples with the higher dopant concentration the abnormal
 grain growth is inhibited and the grain size ranged between 2-10 μm.
 Measurements of dielectric properties were carried out as a function of
 temperature up to 180 °C at different frequencies. The samples doped with
 0.01wt % of Ho, exhibit the high value of dielectric permittivity (er = 2160)
 at room temperature. A nearly flat permittivity-response was obtained in
 specimens with higher additive content. Using a Curie-Weiss law and modified
 Curie-Weiss law the Curie constant (C), Curie temperature (Tc) and a critical
 exponent of nonlinearity (g) were calculated. The Curie temperature of doped
 samples were ranged from 128 to 130°C. The Curie constant for all series of
 samples decrease with increase of dopant concentration and the lowest values
 were observed on samples doped with 0.01 wt % of holmium.

/pdf/microstructural-and-dielectrical-characterization-of-ho-5e6by7bvbx.pdf

Milos Marjanovic

Papers

On the Recoverable and Permanent Components of NBTI in p-Channel Power VDMOSFETs

DIELECTRIC PROPERTIES OF La/Mn CODOPED BARIUM TITANATE CERAMICS

A Transient Modeling of the Thermoelectric Generators for Application in Wireless Sensor Network Nodes

Electrical characteristics of Er doped BaTiO3 ceramics

Microstructural and Dielectrical Characterization of Ho Doped BaTiO3 Ceramics