scispace - formally typeset
Search or ask a question
Topic

Temperature coefficient

About: Temperature coefficient is a research topic. Over the lifetime, 14126 publications have been published within this topic receiving 202714 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, a theoretical model for the dependence of the diode forward voltage (Vf) on junction temperature (Tj) was developed, and an expression for dVf∕dT was derived that took into account all relevant contributions to the temperature dependence of Vf including the intrinsic carrier concentration, the band-gap energy, and the effective density of states.
Abstract: A theoretical model for the dependence of the diode forward voltage (Vf) on junction temperature (Tj) is developed. An expression for dVf∕dT is derived that takes into account all relevant contributions to the temperature dependence of the forward voltage including the intrinsic carrier concentration, the band-gap energy, and the effective density of states. Experimental results on the junction temperature of GaN ultraviolet light-emitting diodes are presented. Excellent agreement between the theoretical and experimental temperature coefficient of the forward voltage (dVf∕dT) is found. A linear relation between the junction temperature and the forward voltage is found.

397 citations

Journal ArticleDOI
TL;DR: The origin of an apparent 'band-like', negative temperature coefficient of the mobility (dmu/dT<0) in spin-coated films of 6,13-bis(triisopropylsilylethynyl)-pentacene is investigated and optical spectroscopy of gate-induced charge carriers is used to show that, at low temperature and small lateral electric field, charges become localized onto individual molecules in shallow trap states, but that a moderate lateralElectric field
Abstract: The mobility mu of solution-processed organic semiconductors has improved markedly to room-temperature values of 1-5 cm(2) V(-1) s(-1). In spite of their growing technological importance, the fundamental open question remains whether charges are localized onto individual molecules or exhibit extended-state band conduction like those in inorganic semiconductors. The high bulk mobility of 100 cm(2) V(-1) s(-1) at 10 K of some molecular single crystals provides clear evidence that extended-state conduction is possible in van-der-Waals-bonded solids at low temperatures. However, the nature of conduction at room temperature with mobilities close to the Ioffe-Regel limit remains controversial. Here we investigate the origin of an apparent 'band-like', negative temperature coefficient of the mobility (dmu/dT<0) in spin-coated films of 6,13-bis(triisopropylsilylethynyl)-pentacene. We use optical spectroscopy of gate-induced charge carriers to show that, at low temperature and small lateral electric field, charges become localized onto individual molecules in shallow trap states, but that a moderate lateral electric field is able to detrap them resulting in highly nonlinear, low-temperature transport. The negative temperature coefficient of the mobility at high fields is not due to extended-state conduction but to localized transport limited by thermal lattice fluctuations.

396 citations

Journal ArticleDOI
TL;DR: In this article, it is shown that the combined mechanical, thermal and electrical interaction between the filler particles via their electrical contacts and the surrounding polymer host matrix are responsible for the properties of the composite material.
Abstract: Conducting polymer composites become increasingly important for technical applications. In this article, the resulting electrical properties of such materials are illustrated by a variety of experimental examples. It is shown that the combined mechanical, thermal and electrical interaction between the filler particles via their electrical contacts and the surrounding polymer host matrix are responsible for the properties of the composite material. A short review is given of the theoretical background for the understanding of the electrical transport in such materials. The arrangement of the filler particles and the resulting conductivity can be described either by percolation or by effective medium theories. It can also be related to different types of charge carrier transport processes depending on the internal composite structure. Special emphasis is given to the microstructure of the filler particles such as size, hardness, shape and their electrical and thermal conductivities. A detailed analysis of the physics of the contact spots and the temperature development during current flow at the contact is given. It is shown that the polymer matrix has a strong influence on the electrical conductivity due to its elastic properties and the response to external thermal and mechanical stimulation. Strong changes in the electrical conductivity of conducting polymer composites can be realized either by thermal stimuli, leading to a positive and negative temperature coefficient in resistivity, or by applying mechanical stress. By using nonlinear fillers an additional degree of functionality can be achieved with conducting polymers.

381 citations

Journal ArticleDOI
TL;DR: In this article, the dielectric, ferroelectric and piezoelectric properties of perovskite and bismuth layered-structured Ferroelectric (BLSF) ceramics are described as superior candidates for lead-free piezolectric materials to reduce environmental damage.
Abstract: The dielectric, ferroelectric and piezoelectric properties of perovskite ferroelectric and bismuth layered-structured ferroelectric (BLSF) ceramics are described being superior candidates for lead-free piezoelectric materials to reduce environmental damage. Perovskite-type ceramics seem to be suitable for actuator and high-power applications that require a large piezoelectric constant, d33, and a high Curie temperature, Tc, or a depolarization temperature, Td (>200 °C). For BaTiO3-based solid solutions, (1-x)BaTiO3–x(Bi0.5K0.5)TiO3 (BT–BKT100x) ceramics, Tc increases with increasing amount of x. The BT–BKT20 + MnCO3 (0.1 wt %) ceramic shows a high Tc greater than 200 °C and an electromechanical coupling factor of k33 =0.35. In the case of a(Bi1/2Na1/2)TiO3–b(Bi1/2K1/2)TiO3–cBaTiO3 [BNBK (100a/100b/100c)] solid solution ceramics, d33 is 191 pC/N for BNBK (85.2/2.8/12). KNbO3 (KN)-based ceramics are also a candidate for lead-free piezoelectrics. In Mn-doped KN ceramics, a higher k33 of 0.507 is obtained for KN + MnCO3 (0.1 wt %). On the other hand, BLSF ceramics seem to be excellent candidates as piezoelectric sensors for high temperatures and ceramic resonators with a high mechanical quality factor, Qm, and a low temperature coefficient of resonance frequency, TC-f. The k33 value of the donor (Nb)-doped and grain-oriented (HF) Bi4Ti3-xNbxO12 (BITN-x) ceramic is 0.39 for x=0.08 and is able to keep the same stable value up to 350 °C. Nd(0.01) and V(0.75) co-doped Bi4Ti3O12 ceramics, BNTV(0.01, 0.75), show a relatively low TC-f. Bi3TiTaO9 (BTT)-based solid solution, Srx-1Bi4-xTi2-xTaxO9 [SBTT2(x)] (1x2), displays the high Qm value (=13500) in (p)-mode at x=1.25. For resonator applications, (Sr1-xCax)2Bi4Ti5O18 (SCBT) (0x0.5) ceramics are suitable.

375 citations

Journal ArticleDOI
TL;DR: In this article, the dielectric properties of single-phase ceramics in the TiO2-rich region of the BaO-TiO2 system were investigated.
Abstract: The dielectric properties of ceramics in the TiO2-rich region of the BaO-TiO2 system were investigated. In the composition range between BaTi4O9 and TiO2, another compound, Ba2Ti9O20, can be obtained when calcining and sintering conditions are controlled carefully. When dense and single-phase, this ceramic has excellent dielectric and physical properties. At 4 GHz, the dielectric K= 39.8, Q= 8000, and τK (temperature coefficient of dielectric constant) =−24 ± 2 ppm/°C.

363 citations


Network Information
Related Topics (5)
Dielectric
169.7K papers, 2.7M citations
91% related
Thin film
275.5K papers, 4.5M citations
89% related
Silicon
196K papers, 3M citations
89% related
Amorphous solid
117K papers, 2.2M citations
88% related
Band gap
86.8K papers, 2.2M citations
87% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023206
2022387
2021391
2020408
2019444
2018511