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You searched for subject:(lanthanum silicate). Showing records 1 – 3 of 3 total matches.

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1. Elias, Daniel Ricco. Síntese e caracterização de pós de silicato de lantânio tipo apatita para eletrólito em SOFC.

Degree: Mestrado, Tecnologia Nuclear - Materiais, 2014, University of São Paulo

A temperatura de operação de células a combustível de óxido sólido (SOFCs) que utilizam zirconia estabilizada com itria (YSZ) como eletrólito é 1000 °C. Essa alta temperatura gera graves problemas relativos a materiais e vida util da célula. Por isso, condutores iônicos que possuem alta condutividade em temperaturas inferiores são pesquisados atualmente. Estudos mostraram que La10Si6O27 tipo apatita possui alta condutividade iônica de oxigenio, que é comparativamente maior que a de YSZ, a 500 °C, sendo, portanto, um potencial candidato como eletrólito para SOFC. O objetivo do presente trabalho é o desenvolvimento de técnicas de síntese de silicato de lantânio tipo apatita. Rotas inéditas de solgel modificada para sintetizar La9,33Si6O26 são propostas. Volumes estequiométricos de soluções de Na2SiO3 e LaCl3 foram misturados para a formação de gel de Si. Em seguida este gel foi calcinado a 900 °C, lavado, filtrado e tratado novamente a 900 °C. Em outra rota, volumes estequiométricos de soluções de Si (Na2SiO3 ou TEOS) e de La (LaCl3) foram utilizados para obtenção de gel de Si. Em seguida, hidróxido de La foi precipitado pela adição de uma base (NaOH ou NH4OH) ao gel. O material resultante foi calcinado a 900 °C, lavado, filtrado e tratado novamente a 900 °C. Pós de aglomerados fracos e alta sinterabilidade foram obtidos. DRX dos pós mostrou a estrutura de apatita monofásica a 900 °C. Morfologia de ceramica densa foi observada em imagens de MEV da superfície das pastilhas sinterizadas a 1200,1300 e 1400 °C por 4 h. Estas temperaturas e tempo de sinterização são significativas, pois no método convencional temperaturas superiores a 1700 °C e tempos muito maiores são necessários para obtenção de tais cerâmicas. Densidades relativas superiores a 90% foram obtidas através dos métodos propostos. Uma conclusão importante é que TEOS, o reagente usual de alto custo, pode ser substituído por Na2SiO3, de preço muito mais baixo, para obter La9,33Si6O26 tipo apatita.

Solid oxide fuel cell (SOFCs) operating temperature that uses yttria stabilized zirconia (YSZ) as the electrolyte is 1000ºC. This high temperature causes serious problems concerning cell life and materials. Therefore, the ionic conductors which have high conductivity at lower temperature are currently researched. Studies have shown that the composition of La10Si6O27 apatite type has high oxygen ionic conductivity, which is comparably higher than that of YSZ, at 500 °C, it is therefore a potential candidate as for SOFC electrolyte. The objective of the present work is the development of lanthanum silicate with apatite type synthesis techniques. Novel modified solgel routes to synthesize La9.33Si6O26 are proposed. Stoichiometric volumes of Na2SiO3 and LaCl3 solutions were mixed for the formation of Si gel. This gel was calcined at 900 °C, washed, filtered and again thermally treated at 900 °C. In the other route, stoichiometric volumes of Si (Na2SiO3 or TEOS) and La (LaCl3) solutions were used for obtaining Si gel. Then, La hydroxide was precipitated by adding of a…

Advisors/Committee Members: Yamagata, Chieko.

Subjects/Keywords: apatita; apatite; electrolyte; eletrólito; lanthanum silicate; silicato de lantânio; SOFC; SOFC; sol-gel; sol-gel

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Elias, D. R. (2014). Síntese e caracterização de pós de silicato de lantânio tipo apatita para eletrólito em SOFC. (Masters Thesis). University of São Paulo. Retrieved from http://www.teses.usp.br/teses/disponiveis/85/85134/tde-25022014-101948/ ;

Chicago Manual of Style (16th Edition):

Elias, Daniel Ricco. “Síntese e caracterização de pós de silicato de lantânio tipo apatita para eletrólito em SOFC.” 2014. Masters Thesis, University of São Paulo. Accessed August 05, 2020. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-25022014-101948/ ;.

MLA Handbook (7th Edition):

Elias, Daniel Ricco. “Síntese e caracterização de pós de silicato de lantânio tipo apatita para eletrólito em SOFC.” 2014. Web. 05 Aug 2020.

Vancouver:

Elias DR. Síntese e caracterização de pós de silicato de lantânio tipo apatita para eletrólito em SOFC. [Internet] [Masters thesis]. University of São Paulo; 2014. [cited 2020 Aug 05]. Available from: http://www.teses.usp.br/teses/disponiveis/85/85134/tde-25022014-101948/ ;.

Council of Science Editors:

Elias DR. Síntese e caracterização de pós de silicato de lantânio tipo apatita para eletrólito em SOFC. [Masters Thesis]. University of São Paulo; 2014. Available from: http://www.teses.usp.br/teses/disponiveis/85/85134/tde-25022014-101948/ ;


University of North Texas

2. Chen, Chao-Hsu. Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries.

Degree: 2014, University of North Texas

Solid state lithium ion electrolytes are important to the development of next generation safer and high power density lithium ion batteries. Perovskite-structured LLT is a promising solid electrolyte with high lithium ion conductivity. LLT also serves as a good model system to understand lithium ion diffusion behaviors in solids. In this thesis, molecular dynamics and related atomistic computer simulations were used to study the diffusion behavior and diffusion mechanism in bulk crystal and grain boundary in lithium lanthanum titanate (LLT) solid state electrolytes. The effects of defect concentration on the structure and lithium ion diffusion behaviors in LLT were systematically studied and the lithium ion self-diffusion and diffusion energy barrier were investigated by both dynamic simulations and static calculations using the nudged elastic band (NEB) method. The simulation results show that there exist an optimal vacancy concentration at around x=0.067 at which lithium ions have the highest diffusion coefficient and the lowest diffusion energy barrier. The lowest energy barrier from dynamics simulations was found to be around 0.22 eV, which compared favorably with 0.19 eV from static NEB calculations. It was also found that lithium ions diffuse through bottleneck structures made of oxygen ions, which expand in dimension by 8-10% when lithium ions pass through. By designing perovskite structures with large bottleneck sizes can lead to materials with higher lithium ion conductivities. The structure and diffusion behavior of lithium silicate glasses and their interfaces, due to their importance as a grain boundary phase, with LLT crystals were also investigated by using molecular dynamics simulations. The short and medium range structures of the lithium silicate glasses were characterized and the ceramic/glass interface models were obtained using MD simulations. Lithium ion diffusion behaviors in the glass and across the glass/ceramic interfaces were investigated. It was found that there existed a minor segregation of lithium ions at the glass/crystal interface. Lithium ion diffusion energy barrier at the interface was found to be dominated by the glass phase. Advisors/Committee Members: Du, Jincheng, Brostow, Witold, 1934-, Shepherd, Nigel Dexter.

Subjects/Keywords: Solid state electrolytes; lithium ion battery; molecular dynamics; nudge elastic band; diffusion coefficients; lithium silicate; Lithium ion batteries.; Lanthanum.; Titanates.; Diffusion  – Computer simulation.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chen, C. (2014). Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries. (Thesis). University of North Texas. Retrieved from https://digital.library.unt.edu/ark:/67531/metadc700110/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Chen, Chao-Hsu. “Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries.” 2014. Thesis, University of North Texas. Accessed August 05, 2020. https://digital.library.unt.edu/ark:/67531/metadc700110/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Chen, Chao-Hsu. “Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries.” 2014. Web. 05 Aug 2020.

Vancouver:

Chen C. Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries. [Internet] [Thesis]. University of North Texas; 2014. [cited 2020 Aug 05]. Available from: https://digital.library.unt.edu/ark:/67531/metadc700110/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Chen C. Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries. [Thesis]. University of North Texas; 2014. Available from: https://digital.library.unt.edu/ark:/67531/metadc700110/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


North Carolina State University

3. Jur, Jesse Stephen. Lanthanide-based Oxides and Silicates for High-K Gate Dielectric Applications.

Degree: PhD, Materials Science and Engineering, 2007, North Carolina State University

The ability to improve performance of the high-end metal oxide semiconductor field effect transistor (MOSFET) is highly reliant on the dimensional scaling of such a device. In scaling, a decrease in dielectric thickness results in high leakage current between the electrode and the substrate by way of direct tunneling through the gate dielectric. Observation of a high leakage current when the standard gate dielectric, SiO2, is decreased below a thickness of 1.5 nm requires engineering of a replacement dielectric that is much more scalable. This high- dielectric allows for a physically thicker oxide, reducing leakage current. Integration of select lanthanide-based oxides and silicates, in particular lanthanum oxide and silicate, into MOS gate stack devices is examined. The quality of the high-K dielectrics is monitored electrically to determine properties such as equivalent oxide thickness, leakage current density and defect densities. In addition, analytical characterization of the dielectric and the gate stack is provided to examine the materialistic significance to the change of the electrical properties of the devices. It is shown that optimization of low-temperature processing can result in MOS devices with an equivalent oxide thickness (EOT) as low 5 Å and a leakage current density of 5.0 A⁄cm2. High-temperature processing, consistent with a MOSFET source-drain activation anneal, yields MOS devices with an EOT as low as 1.1 nm after optimization of the TaN/W electrode properties. The decrease in the device effective work function (phi_M,eff) observed in these samples is examined in detail. First, as a La2O3 capping layer on HfSiO(N), the shift yields ideal-phi_M,eff values for nMOSFET deices (4.0 eV) that were previously inaccessible. Other lanthanide oxides (Dy, Ho and Yb) used as capping layers show similar effects. It is also shown that tuning of phi_M,eff can be realized by controlling the extent of lanthanide-silicate formation. This research, conducted in conjunction with SEMATECH and the SRC, represents a significant technological advancement in realizing 45 and sub-45 nm MOSFET device nodes. Advisors/Committee Members: Angus Kingon, Committee Chair (advisor), Gregory Parsons, Committee Member (advisor), Jon-Paul Maria, Committee Member (advisor), Mark Johnson, Committee Member (advisor).

Subjects/Keywords: dc magnetron sputtering; physical vapor deposition; tungsten oxide; tungsten; W; tantalum nitride; TaN; lanthanum; lanthanum oxide; La; La2O3; La2SiO5; lanthanum silicate; La2Si2O7; Ho; holmium; holmium oxide; cation diffusion; back-side SIMS; secondary ion mass spectroscopy; SIMS; XRD; x-ray diffraction; molecular beam deposition; PMA; XPS; x-ray photoemission spectroscopy; post metallization anneal; RCA; chemical oxide; metal oxide semiconductor field effect transistor; MBE; silica; SiO2; interfacial layer; gate dielectric; dielectric; silicate; oxide; high-kappa; EOT; equivalent oxide thickness; high-k; band diagram; valance band offset; conduction band offset; band gap energy; effective work function; work function; voltage shift; threshold voltage; flat band voltage; leakage current; capacitance; mobility; electronic materials; scaling; Moore?s Law; MIS; MOS; MOSFET; high resolution transmission electron microscopy; HRTEM; RTA; rapid thermal anneal; PVD; tantalum; Ta; gate electrode; metal electrode; hafnium silicate; hafnium oxide; hafnium; ytterbium; ytterbium oxide; Yb; dysprosium oxide; dysprosium; Dy; E-beam evaporation; thermal evaporation; forming gas anneal; ozone; ammonia anneal; FGA

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Jur, J. S. (2007). Lanthanide-based Oxides and Silicates for High-K Gate Dielectric Applications. (Doctoral Dissertation). North Carolina State University. Retrieved from http://www.lib.ncsu.edu/resolver/1840.16/5447

Chicago Manual of Style (16th Edition):

Jur, Jesse Stephen. “Lanthanide-based Oxides and Silicates for High-K Gate Dielectric Applications.” 2007. Doctoral Dissertation, North Carolina State University. Accessed August 05, 2020. http://www.lib.ncsu.edu/resolver/1840.16/5447.

MLA Handbook (7th Edition):

Jur, Jesse Stephen. “Lanthanide-based Oxides and Silicates for High-K Gate Dielectric Applications.” 2007. Web. 05 Aug 2020.

Vancouver:

Jur JS. Lanthanide-based Oxides and Silicates for High-K Gate Dielectric Applications. [Internet] [Doctoral dissertation]. North Carolina State University; 2007. [cited 2020 Aug 05]. Available from: http://www.lib.ncsu.edu/resolver/1840.16/5447.

Council of Science Editors:

Jur JS. Lanthanide-based Oxides and Silicates for High-K Gate Dielectric Applications. [Doctoral Dissertation]. North Carolina State University; 2007. Available from: http://www.lib.ncsu.edu/resolver/1840.16/5447

.