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Paper Titles
Preface
Sintering Fundamentals: Historical Aspects
p.1
Sintering Simplified: Surface Area, Density, and Grain Size Relations
p.50
Rheology and Kinetics of Pressure Sintering
p.76
Dilatometry Coupled with Mass Spectrometry as Instrument for Process Control in Sintering of Powder Metallurgy Steels
p.106
Sintering Mechanisms of Functionally Graded Cemented Carbides
p.116
Doped Ceria Based Solid Oxide Fuel Cell Electrolytes and their Sintering Aspects: An Overview
p.199
Sintering and Microstructural Modification of Seeded and Neodymium Doped Lanthanum Hexaaluminate
p.237

Sintering and Microstructural Modification of Seeded and Neodymium Doped Lanthanum Hexaaluminate

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Abstract:

The effect of (i) heterogeneous nucleation by seeding or (ii) doping with neodymium on the formation of lanthanum hexaaluminate was studied during sol to gel conversion. The resultant dried gels were calcined at various temperatures starting from 1100°C to 1600°C for 2 h to study the phase evolution and microstructure.The combined effects of advanced sol gel processing and heterogeneous nucleation promoted the formation of lanthanum hexaaluminate phase at lower temperature (1200°C) than the conventional routes (1300°C). Lanthanum hexaaluminate phase was detected at 1200°C and 1300°C in seeded gel (SG) and unseeded gel (UG), respectively. Heterogeneous nucleation of SG decreases the temperature of formation of lanthanum hexaaluminate by 100°C. Single phase lanthanum hexaaluminate was formed at 1600°C in seeded gel whereas trace of lanthanum monoaluminate phase was still present in UG even at 1600°C.On the doped ones, randomly grown platelets of lanthanum magnesium hexaaluminate form a porous interlocking structure. Presence of various percentages of neodymium oxide significantly modifies the porous interlocking microstructure into self-reinforced, card-house like microstructure. Platelets of rare earth rich magnesium hexaaluminate were grown preferentially more than the stoichiometric rare earth magnesium hexaaluminate at elevated temperature greater than 1450°C. Rare earth rich magnesium hexaaluminate platelets formed the skeleton of a card house structure and the tiny platelets of stoichiometric rare earth magnesium hexaaluminate fill the rest. Lattice parameters of the hexagonal unit cell (c and a) decrease, relative density increases and pore size distribution remained almost unaltered with the increment of doping concentration.

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Periodical:

Materials Science Forum (Volume 835)

Pages:

237-250

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.835.237

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Online since:

January 2016

Authors:

P. Jana, P.S. Jayan, S. Mandal, Koushik Biswas*

Keywords:

Doping, Lanthanum Hexaaluminate, Microstructure, Seeding, Sintering

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