Characterization of gas sensing HfO2 coatings synthesized by spray pyrolysis technique

Ávila-García, A.; Garcı́a-Hipólito, M.

doi:10.1016/j.snb.2008.02.031

Cited by 17 publications

(6 citation statements)

References 22 publications

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“…Its high dielectric constant and insulating properties [16] allow its application as a dielectric material with relatively high refractive index and wide band gap, as well in the field of optical coatings and metal-oxide semiconductor devices of the next generation [17]. HfO 2 films have been used as sensors to detect CO gas [18], and sensing characteristics to propane of these films synthesized by the ultrasonic spray pyrolysis (USP) technique were recently studied [19]. HfO 2 can also be used for protective coatings due its thermal stability and hardness near to diamond in its tetragonal phase [20].…”

Section: Introductionmentioning

confidence: 99%

Blue-yellow photoluminescence from Ce3+→Dy3+ energy transfer in HfO2:Ce3+:Dy3+ films deposited by ultrasonic spray pyrolysis

Martínez-Martínez

Lira

Speghini

et al. 2011

Journal of Alloys and Compounds

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Section: Introductionmentioning

confidence: 99%

Blue-yellow photoluminescence from Ce3+→Dy3+ energy transfer in HfO2:Ce3+:Dy3+ films deposited by ultrasonic spray pyrolysis

Martínez-Martínez

Lira

Speghini

et al. 2011

Journal of Alloys and Compounds

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“…It is well known that pure, stoichiometric HfO 2 is an insulator with ionic conductivity, mainly attributed to O − 2 . However, point defects such as oxygen vacancies may generate intermediate energy levels and bands in the band gap of HfO 2 making it an n-type semiconductor [43][44][45]. DRS analyses show that our HfO 2 powder contains point defects such as oxygen vacancies.…”

Section: Gas Sensing Mechanismsmentioning

confidence: 94%

Enhanced room temperature sensitivity of undoped HfO2 nanoparticles towards formaldehyde gas

Chattopadhyay

Nayak

2021

Appl. Phys. A

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Hafnium oxide (HfO 2 ) nanoparticulate powders were synthesized via a single step sol gel route using citric acid and ethylene glycol as chelating agent and polymerizing agent, respectively. In order to burn off the volatile components and produce crystalline HfO 2 nanoparticles, the powders were calcined at moderately high temperatures ranging from 500 to 800 °C for 1 h each. The crystal structures of the nanoparticles were ascertained by powder X-ray diffraction. The nanocrystals in powder form had monoclinic structure and preferred orientation of the nanocrystals along (−111) direction was evident. The morphologies of the HfO 2 nanopowders were studied by Field Emission Scanning Electron Microscope (FESEM). Morphologies of the nanopowder were observed to change with calcination temperatures. The optical properties of the HfO 2 nanoparticles were evaluated by UV-Vis Diffuse Reflectance Spectroscopy (DRS). A small change in the band gap energy of HfO 2 nanoparticles was observed with a change in the calcination temperature. In order to study the electrical and gas sensing properties of HfO 2 nanoparticles, the powders were pressed into pellets with 12.0 mm diameter and 1.5 mm thickness. Gas sensing properties of HfO 2 pellets were investigated by exposing them to formaldehyde gas inside closed chambers. The sensitivity of HfO 2 towards formaldehyde gas initially increased with an increase in the calcination temperature due to increased porosity and decreased resistance of the HfO 2 pellet. The HfO 2 powder calcined at 700 °C showed highest sensitivity of 91.2% towards 264 ppm formaldehyde gas. The sensitivity declined with further increase in the calcination temperature because the HfO 2 pellet became less porous thereby. Selectivity of the HfO 2 sensor was tested with three volatile organic compound gases: acetone, ethanol and formaldehyde. Highest response was recorded for the formaldehyde gas.

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“…However, despite those great achievements for spray pyrolysis, several issues still remain. First, spray pyrolysis has generally been adopted for the synthesis of metal oxides (e.g., high‐purity Al 2 O 3 , MgO, ZnO, HfO 2 and ZrO 2 , complex oxides of BaTiO 3 and SrTiO 3 , oxide solid solution of Y‐stabilized ZrO 2 , and composites such as Pt‐supported by Al 2 O 3 or ZrO 2 ) . Only a few studies have reported its use for the preparation of non‐oxide ceramic materials such as nitrides, borides, and carbides .…”

Section: Introductionmentioning

confidence: 99%

“…First, spray pyrolysis has generally been adopted for the synthesis of metal oxides (e.g., high-purity Al 2 O 3 , MgO, ZnO, HfO 2 and ZrO 2 , complex oxides of BaTiO 3 and SrTiO 3 , oxide solid solution of Y-stabilized ZrO 2 , and composites such as Pt-supported by Al 2 O 3 or ZrO 2 ). [13][14][15][16] Only a few studies have reported its use for the preparation of non-oxide ceramic materials such as nitrides, 17,18 borides, 19 and carbides. 20,21 Even in those studies, expensive oxygen-free precursors (such as polysilazane for Si 3 N 4 synthesis 17 and poly(borazinylamine) 22 or borazine 23 for hBN preparation) and solvents (e.g., dry acetonitrile, 18 benzene 17 and liquid anhydrous ammonia 22,24 ) were often required.…”

Section: Introductionmentioning

confidence: 99%

Facile one‐step high‐temperature spray pyrolysis route toward metal carbide nanopowders

et al. 2018

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Fine ultrahigh‐temperature ceramic (UHTC) powders have found very important applications in many fields. In this work, a facile high‐temperature spray pyrolysis (HTSP) approach is implemented for the synthesis of HfC and TaC UHTC nanopowders starting from organic solvent (e.g., ethanol or 1‐pentanol) solutions of metal precursors (HfCl4 or TaCl5). It is proposed that, during HTSP, the precursor solution droplets would continuously undergo rapid drying, thermolysis (i.e., removal of low molecular weight species such as H2, H2O, and CO), and finally in situ carbothermal reduction (CTR) process to give rise to metal carbide nanopowders. The as‐obtained materials are shown by SEM as uniform and separated nanoparticles (~90 nm), whereas TEM reveals the carbide (e.g., HfC) nanoparticles are actually even smaller (~10‐20 nm) and embedded in amorphous carbon from excess solvent decomposition. It is found that among different processing parameters, the organic solvent used and the metal precursor concentration could largely influence the formation of metal carbide. In addition, lower HTSP temperatures (≤~1500°C for HfC) only lead to oxide‐carbon mixtures while higher temperatures (≥~1650°C) promote carbide formation. The HTSP method developed in this work is simple, low‐cost and efficient, and could potentially be optimized further for future large‐scale manufacturing of ultrafine UHTC nanopowders.

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Characterization of gas sensing HfO2 coatings synthesized by spray pyrolysis technique

Cited by 17 publications

References 22 publications

Blue-yellow photoluminescence from Ce3+→Dy3+ energy transfer in HfO2:Ce3+:Dy3+ films deposited by ultrasonic spray pyrolysis

Blue-yellow photoluminescence from Ce3+→Dy3+ energy transfer in HfO2:Ce3+:Dy3+ films deposited by ultrasonic spray pyrolysis

Enhanced room temperature sensitivity of undoped HfO2 nanoparticles towards formaldehyde gas

Facile one‐step high‐temperature spray pyrolysis route toward metal carbide nanopowders

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