Grain boundary complexion transitions in WO3- and CuO-doped TiO2 bicrystals

Ma, Shuailei; Cantwell, Patrick R.; Pennycook, Timothy J.; Zhou, Naixie; Oxley, Mark P.; Leonard, Donovan N.; Pennycook, Stephen J.; Luo, Jian; Harmer, Martin P.

doi:10.1016/j.actamat.2012.11.044

Cited by 33 publications

(15 citation statements)

References 82 publications

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“…Lastly, we should also recognize the possibility that some of these IGFs exhibit discrete (instead of continuous) thickness (to form Dillon-Harmer GB complexions [23,41]) for certain specific GBs, e.g., some special GBs with low-index grain surfaces, as shown in a prior study for a (001) // (100) GB in a (CuO + SiO 2 ) doped TiO 2 bicrystal specimen [41]. The origin of the discrete thicknesses and the formation of Dillon-Harmer GB complexions can be explained in the same interfacial thermodynamic framework discussed above via incorporating (adding) an oscillatory structural interaction (as a result of a fixed, finite, atomic size using a hard-sphere approximation) in Eq.…”

Section: An Interfacial Thermodynamic Model and The Computed Gb  Diamentioning

confidence: 99%

“…The origin of the discrete thicknesses and the formation of Dillon-Harmer GB complexions can be explained in the same interfacial thermodynamic framework discussed above via incorporating (adding) an oscillatory structural interaction (as a result of a fixed, finite, atomic size using a hard-sphere approximation) in Eq. (3) or the interfacial coefficient f(h) [31,[41][42][43].…”

Section: An Interfacial Thermodynamic Model and The Computed Gb  Diamentioning

confidence: 99%

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Liquid-like grain boundary complexion and sub-eutectic activated sintering in CuO-doped TiO2

et al. 2017

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The eutectic temperature and composition of the TiO 2-CuO system were carefully measured to be 1010  10 C and 83CuO:17TiO 2 , respectively. Subsequently, a TiO 2-CuO phase diagram was computed, representing a correction and major improvement from the phase diagram available in literature. Dilatometry measurements and isothermal sintering experiments unequivocally demonstrated the activated (enhanced) sintering of TiO 2 with the addition of CuO, occurring at as low as >300C below the eutectic temperature. High resolution transmission electron microscopy (HRTEM) characterization of water-quenched specimens revealed the formation of nanometer-thick, liquid-like, intergranular films (IGFs), a type of grain boundary (GB) complexion (a.k.a. 2-D interfacial phase), concurrently with accelerated densification and well below the bulk eutectic temperature. Consequently, activated sintering is explained from the enhanced mass transport in this premelting-like complexion. An interfacial thermodynamic model was used to quantitatively explain and justify the stabilization of liquid-like IGFs below the eutectic temperature and the temperature-dependent IGF thicknesses measured by HRTEM. A GB  diagram was computed, for the first time for a ceramic system, to represent the thermodynamic tendency for general GBs in CuO-doped TiO 2 to disorder.

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Section: An Interfacial Thermodynamic Model and The Computed Gb  Diamentioning

confidence: 99%

Section: An Interfacial Thermodynamic Model and The Computed Gb  Diamentioning

confidence: 99%

Liquid-like grain boundary complexion and sub-eutectic activated sintering in CuO-doped TiO2

et al. 2017

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“…Recently, Harmer et al 3) showed a structural disordering of grain boundary caused by the excess CuO for a CuOdoped TiO 2 bicrystal. The disordering enhances the grain boundary diffusion along and across the grain boundary.…”

Section: Introductionmentioning

confidence: 99%

Low-temperature Sintering Behavior of TiO2 Activated with CuO

Paek

Shin²,

et al. 2016

J. Korean Ceram. Soc

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In TiO 2-CuO systems, low-temperature sinterability was investigated by a conventional sintering method. Sintering temperatures were set at under 950 o C, at which the volume diffusion is inactive. The temperatures are less than the melting point of Ag (961 o C), which is often used as an internal conductor in low-temperature co-fired ceramic technology. To optimize the amount of CuO dopant, various dopant contents were added. The optimum level for enhanced densification was 2 wt% CuO. Excess dopants were segregated to the grain boundaries. The segregated dopants supplied a high diffusion path, by which grain boundary diffusion improved. At lower temperatures in the solid state region, grain boundary diffusion was the principal mass transport mechanism for densification. The enhanced grain boundary diffusion, therefore, improved densification. In this regard, the results of this study prove that the sintering mechanism was the same as that of activated sintering.

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“…vs. T") observed by HRTEM. Lastly, we should also recognize the possibility that some of these IGFs exhibit discrete (instead of continuous) thickness (to form Dillon-Harmer GB complexions [23,41]) for certain specific GBs, e.g., some special GBs with low-index grain surfaces, as shown in a prior study for a (001)//(100) GB in a (CuO þ SiO 2 ) doped TiO 2 bicrystal specimen [41]. The origin of the discrete thicknesses and the formation of Dillon-Harmer GB complexions can be explained in the same interfacial thermodynamic framework discussed above via incorporating (adding) an oscillatory structural interaction (as a result of a fixed, finite, atomic size using a hard-sphere approximation) in Eq.…”

Section: An Interfacial Thermodynamic Model and The Computed Gb L Diamentioning

confidence: 99%

Probing the densification mechanisms during flash sintering of ZnO

et al. 2017

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a b s t r a c tThe eutectic temperature and composition of the TiO 2 -CuO system were carefully measured to be 1010 ± 10 C and 83CuO:17TiO 2 , respectively. Subsequently, a TiO 2 -CuO phase diagram was computed, representing a correction and major improvement from the phase diagram available in literature. Dilatometry measurements and isothermal sintering experiments unequivocally demonstrated the activated (enhanced) sintering of TiO 2 with the addition of CuO, occurring at as low as >300 C below the eutectic temperature. High resolution transmission electron microscopy (HRTEM) characterization of waterquenched specimens revealed the formation of nanometer-thick, liquid-like, intergranular films (IGFs), a type of grain boundary (GB) complexion (a.k.a. 2-D interfacial phase), concurrently with accelerated densification and well below the bulk eutectic temperature. Consequently, activated sintering is explained from the enhanced mass transport in this premelting-like complexion. An interfacial thermodynamic model was used to quantitatively explain and justify the stabilization of liquid-like IGFs below the eutectic temperature and the temperature-dependent IGF thicknesses measured by HRTEM. A GB l diagram was computed, for the first time for a ceramic system, to represent the thermodynamic tendency for general GBs in CuO-doped TiO 2 to disorder.

show abstract

Grain boundary complexion transitions in WO3- and CuO-doped TiO2 bicrystals

Cited by 33 publications

References 82 publications

Liquid-like grain boundary complexion and sub-eutectic activated sintering in CuO-doped TiO2

Liquid-like grain boundary complexion and sub-eutectic activated sintering in CuO-doped TiO2

Low-temperature Sintering Behavior of TiO2 Activated with CuO

Probing the densification mechanisms during flash sintering of ZnO

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