Enhanced electrical conductivity of ultrafine-grained 8Y2O3 stabilized ZrO2 produced by two-step sintering technique

Hesabi, Z. Razavi; Mazaheri, Mehdi; Ebadzadeh, T.

doi:10.1016/j.jallcom.2010.01.046

Cited by 33 publications

(7 citation statements)

References 17 publications

(30 reference statements)

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“…The activation energy is estimated to be 0.61 eV in the relevant SOFC operating temperature range of 700–800°C. The estimated activation energy values for honeycomb structured 8YSZ specimens used in the present study were found to be lower than the earlier reported value by Razavi and Mondal complementing relatively high ionic conductivity values observed in the present study.…”

Section: Resultscontrasting

confidence: 70%

Colloidal Shaping of 8 mol% Yttria‐Stabilized Zirconia Electrolyte Honeycomb Structures by Microwave‐Assisted Thermal Gelation of Methyl Cellulose

Rajeswari

Biswas

Suresh

et al. 2012

Int J Applied Ceramic Tech

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Eight mol% Yttria‐stabilized zirconia, the most commonly employed electrolyte material for solid oxide fuel cells (SOFC), was shaped into honeycomb structures by thermally induced gelation of aqueous zirconia slurry containing methyl cellulose using microwave irradiation. The green honeycomb samples were subjected to green density and green compressive strength measurements revealing a uniform gelation and hence a relatively higher strength for microwave irradiated samples. The green honeycomb samples were further sintered to crack‐free dense honeycombs (>99% TD) at 1525°C for 1 h. Honeycomb samples were characterized for their physical, cellular, and electrical properties. A relatively high ionic conductivity value of 0.07 S/cm at 800°C and corresponding low activation energy of 0.61 eV in the temperature range 700–800°C provide opportunities to explore the development of novel designs for SOFC application.

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Section: Resultscontrasting

confidence: 70%

Colloidal Shaping of 8 mol% Yttria‐Stabilized Zirconia Electrolyte Honeycomb Structures by Microwave‐Assisted Thermal Gelation of Methyl Cellulose

Rajeswari

Biswas

Suresh

et al. 2012

Int J Applied Ceramic Tech

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“…Hence, TSS on 8YSZ controls the grain growth compared to 3Y-TZP due to its cubic crystal structure. TSS has been widely applied to 8YSZ to improve mechanical, electrical as well as the gas permeance via controlling the grain growth [3,9,24,[32][33][34] ) [9]. In addition to the above property, it is necessary to control grain growth to achieve optimum ratio of grain size to electrolyte layer thickness (0.1 < z < 0.3) to control gas permeance value for SOFC [64].…”

Section: Sintering Of 8yszmentioning

confidence: 99%

“…Hesabi et al [9] reported that the TSS is efficient in obtaining fine grain 8YSZ when compared to conventional and microwave sintering with nearly full density. The grain size and conductivity of conventionally sintered sample at 1500°C with a heating rate of 5°C/min, microwave-sintered samples at 1500°C with a heating rate of 50°C/min and TSS with the first-step sintering temperature of 1250°C with no holding time and the second-step sintering temperature of 1050°C with 20 h holding time were compared.…”

Section: Sintering Of 8yszmentioning

confidence: 99%

Two-Step Sintering of Ceramics

Sutharsini¹,

Murugathas²,

RameshSingh³

2018

Sintering of Functional Materials

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Sintering is a critical phase in the production of ceramic bodies. By controlling the density and microstructure formation, sintering now emerged as a processing technology of ceramic materials. Tailoring the structural, mechanical, electrical, magnetic and optical properties is widening the application of ceramics in various fields. Recently, many advanced sintering methods have reported to fabricate ceramic materials with controlled properties. Two-stage sintering (TSS) is one of the simple and cost-effective methods to obtain near-theoretical density materials with controlled grain growth without adding any dopants. Many recent works have reported the use of TSS as a processing method to fabricate nanoceramics for various applications. With this background, this chapter reviews the advantages of TSS in ceramic preparation based on properties and materials and explores the future directions.

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“…Nanocrystalline 8YSZ was produced by Mazaheri et al [70][71][72] via glycine-nitrate process in a muffle furnace using ZrO(NO 3 ) 2 ?6H 2 O and Y(NO 3 ) 3 ?6H 2 O as sources of oxidants. In order to break the foamy agglomerates, the as-synthesised nanocrystalline agglomerates were ground in a planetary ball mill.…”

Section: Powder Synthesismentioning

confidence: 99%

“…The optimised schedule ( T 1 = 1250°C; T 2 = 1050°C for 20 h) corresponded to 97% TD and 295 nm. 72 Muccillo and Muccillo 141 obtained sintered 8YSZ specimens with >97% TD and grain size of 580 nm by TSS ( T 1 = 1330°C; T 2 = 1230°C for 20 h).…”

Section: Sintering Schedules In Conventional Furnacesmentioning

confidence: 99%

Obtaining highly dense YSZ nanoceramics by pressureless, unassisted sintering

Hotza

García

Castro

2015

International Materials Reviews

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For technological applications, zirconia is commonly blended with other oxides to stabilise the tetragonal and/or cubic phases at low temperature, being yttria the most frequently added dopant. It is generally desirable to obtain highly dense ceramics while maintaining grain sizes in the nanoscale (,100 nm). Small grains contribute to stabilise the tetragonal phase and to improve the toughness and flexural strength. Moreover, a higher ionic conductivity for cubic zirconia electrolytes is achieved with smaller grain size and lower thickness of the intergranular regions. The sintering onset temperatures required for nanometric particles are significantly reduced when compared to conventional micrometric powders. However, densification is generally accompanied by an undesirable grain coarsening. A Ramp and Hold Sintering (RHS) is the simplest densification schedule, consisting of heating up to the peak temperature followed by a holding time at that temperature. Another approach, called Two-Step Sintering (TSS) is based on the principle that the activation energy for grain growth is lower than the activation energy of densification. The key elements in this method are heating up to a high temperature to achieve a density .75% Theoretical Density (TD) to render the pores unstable, and then cooling down rapidly to a lower temperature to finish sintering and hinder grain growth. Alternatively, considerable efforts have been made in increasing the heating rate and/or reducing the hold time at the peak temperature during sintering cycles in processes that are generally referred to as 'Fast Firing' (FF) or 'rapid sintering'. This review summarises the attempts in the literature for obtaining dense monolithic nanocrystalline Yttria-Stabilized Zirconia (YSZ) ceramics by pressureless sintering schedules carried out in conventional furnaces. RHS, FF and TSS schedules are reported only from YSZ as starting powders, i.e. without the aid of any additional dopant or grain growth inhibitor. For the sake of comparison, the discussion is focused mainly on YSZ nanoceramics with final densities .99% TD and average grain size ,100 nm. Powder and shaping effects on microstructure and properties of bulk nanoceramics are discussed. A comparison among sintering approaches is then made taking into account the microstructural development of the nanostructures and some key properties of the products.

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Enhanced electrical conductivity of ultrafine-grained 8Y2O3 stabilized ZrO2 produced by two-step sintering technique

Cited by 33 publications

References 17 publications

Colloidal Shaping of 8 mol% Yttria‐Stabilized Zirconia Electrolyte Honeycomb Structures by Microwave‐Assisted Thermal Gelation of Methyl Cellulose

Colloidal Shaping of 8 mol% Yttria‐Stabilized Zirconia Electrolyte Honeycomb Structures by Microwave‐Assisted Thermal Gelation of Methyl Cellulose

Two-Step Sintering of Ceramics

Obtaining highly dense YSZ nanoceramics by pressureless, unassisted sintering

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