Photoluminescence study of ZnO varistor stability

Ramanachalam, M. S.; Rohatgi, A.; Carter, W. B.; Schaffer, J.P.; Gupta, T. K.

doi:10.1007/bf02659707

Cited by 75 publications

(47 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The second one originates from its granular nature. It is well known that polycrystalline samples bear a large volume fraction of the material with high concentration of defects (mostly charged), namely grain boundaries (GB) 22 . The grain interiors bear relatively much lower concentration of defects.…”

mentioning

confidence: 99%

Interplay of defects in 1.2 MeV Ar irradiated ZnO

Chattopadhyay

Dutta

Jana

et al. 2010

Journal of Applied Physics

View full text Add to dashboard Cite

Defect characterization in 1.2 MeV Ar8+ irradiated polycrystalline ZnO has been carried out by x-ray diffraction (XRD), scanning electron microscopy (SEM) along with electrical resistivity, and photoluminescence (PL) measurements at room temperature (RT). Interestingly, irradiation with the initial fluence (1×1015 ions/cm2) changes the color of the sample from white to orange while the highest irradiation fluence (5×1016 ions/cm2) makes it dark reddish brown that appears as black. XRD study reveals no significant change in the average grain size of the samples with irradiation fluence. Increase in surface roughness due to sputtering is clearly visible in SEM with highest fluence of irradiation. RT PL spectrum of the unirradiated sample shows intense ultraviolet (UV) emission (∼3.27 eV) and less prominent defect level emissions (2–3 eV). The overall emission is largely quenched due to initial irradiation fluence. Increasing the fluence of Ar beam further, UV emission is enhanced along with prominent defect level emissions. Remarkably, the resistivity of the irradiated sample with highest fluence is reduced by four orders of magnitude compared to that of the unirradiated sample. This is due to an increase in donor concentration as well as their mobility induced by high fluence of irradiation. Change in color in the irradiated samples indicates dominant presence of oxygen vacancies. It is now well known that oxygen vacancies are deep donors in ZnO. So oxygen vacancies, in principle, are not the source of conductivity in ZnO at RT. Simultaneous evolution of coloration and conductivity in ZnO, as is seen in this study, indicate that oxygen vacancies strongly influence the stability of shallow donors, presumably zinc interstitial related (highly mobile Zn interstitials also need to form defect pair/complex to be stable), which act as major source of carriers. Such a contention is in conformity with most recent theoretical calculations.

show abstract

mentioning

confidence: 99%

Interplay of defects in 1.2 MeV Ar irradiated ZnO

Chattopadhyay

Dutta

Jana

et al. 2010

Journal of Applied Physics

View full text Add to dashboard Cite

show abstract

“…Compared with doping other elements, (Nb, Sm, Si)-doped varistors possess ultrahigh dielectric constant of 9.5 9 10 4 . The varistor action observed in ZnO ceramics is explained by the presence of Schottky type energy barrier [21] at the grain boundaries. In analogy to the model for a ZnO based varistor [22], the potential barriers for TiO 2 -based varistor created from the phase segregations.…”

Section: Resultsmentioning

confidence: 96%

Influence of Sm2O3 on electrical performance of (Nb, Si)-doped TiO2-based varistor

Zhu

Xiang

et al. 2015

J Mater Sci: Mater Electron

View full text Add to dashboard Cite

In this work, TiO 2 -based varistor ceramics doped with Nb 2 O 5 , SiO 2 and Sm 2 O 3 are prepared by using conventional solid state synthesis. X-ray diffractometry, scanning electron microscopy, energy dispersive spectrometer and direct current electrical measurement are used to study phase composition, microstructure and nonlinear properties. It is found that the second phase emerges at grain boundary, having a great influence on nonlinear electrical behaviors. Breakdown voltage E 1mA initially decreases and then increases with increasing of Sm 2 O 3 content. The minimum of breakdown voltage E 1mA (9.3 V/mm) occurs at the composition of 99.0 %TiO 2 -0.5 %Nb 2 O 5 -0.3 %SiO 2 -0.2 %Sm 2 O 3 . Relative dielectric constant initially increases and then decreases. When the content of Sm 2 O 3 increases to 0.3 %, the varistor has ultrahigh dielectric constant, which is consistent with its narrowest grain-boundary barriers. The nonlinear coefficient increases from 2.51 to 4.13 with increase of Sm 2 O 3 from 0.0 to 0.4 %, and varistor of 98.8 %TiO 2 -0.5 %Nb 2 O 5 -0.3 %SiO 2 -0.4 %Sm 2 O 3 owns the highest grain-boundary barriers.

show abstract

“…[10] Some other authors proposed the visible luminescence of ZnO is attributed to the Zn I ® V Zn transition. [11,12] At low temperatures, ZnO is a nonstoichiometric oxide and has Zn I sites, which are located at around 0.5 eV below the bottom of the conduction band. The occurrence of Zn I sites results in Zn vacancies with energies of about 0.7 eV above the top of the valence band.…”

Section: Zno/polymer Compositesmentioning

confidence: 99%

Generating Blue and Red Luminescence from ZnO/Poly(ethylene glycol) Nanocomposites Prepared Using an In‐Situ Method

Abdullah¹,

Morimoto²,

Okuyama³

2003

Adv Funct Materials

147

View full text Add to dashboard Cite

The peak of the luminescence spectrum of zinc oxide (ZnO) is usually observed above 500 nm (yellow region). By in‐situ growth of ZnO nanoparticles in a poly(ethylene glycol) (PEG) matrix, we have succeeded in producing ZnO/polymer composites with stable luminescence peaks down to 465 nm (blue region). The unbalanced precursor molarity approach, where the molarity of one precursor (LiOH) is several times larger than the molarity represented by a chemical reaction balance, was used. The blue luminescence, which was accompanied by an enhancement of luminescence intensity, was observed at very high LiOH concentrations. This was probably due to the simultaneous reduction in the crystalline size and improvement in the crystallinity. Doping ZnO nanoparticles with europium also generated a red luminescence at 616 nm, due to the 5D0 →7F2 transition of Eu ions.

show abstract

Photoluminescence study of ZnO varistor stability

Cited by 75 publications

References 17 publications

Interplay of defects in 1.2 MeV Ar irradiated ZnO

Interplay of defects in 1.2 MeV Ar irradiated ZnO

Influence of Sm2O3 on electrical performance of (Nb, Si)-doped TiO2-based varistor

Generating Blue and Red Luminescence from ZnO/Poly(ethylene glycol) Nanocomposites Prepared Using an In‐Situ Method

Contact Info

Product

Resources

About