Phase structure and thermal evolution in coating films and powders obtained by sol-gel process: Part II. ZrO2–2.5 mole% Y2O3

1997 ◽  
Vol 12 (10) ◽  
pp. 2594-2601 ◽  
Author(s):  
R. Caruso ◽  
E. Benavídez ◽  
O. de Sanctis ◽  
M. C. Caracoche ◽  
P. C. Rivas ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Phase Structure ◽  
Thermal Evolution ◽  
Thermal Analyses ◽  
Sol Gel ◽  
Tetragonal Zirconia ◽  
Fast Diffusion ◽  
Coating Films ◽  
Angular Correlations ◽  
Heating And Cooling

Powders and coatings of zirconia doped with 2.5 mole% yttria have been produced via the sol-gel route. The phase structure and subsequent thermal evolution in heating and cooling cycles have been investigated using mainly perturbed angular correlations spectroscopy. Thermal analyses and XRD as a function of temperature have also been performed to obtain complementary information. Upon heating, the amorphous gels crystallized into the tetragonal structure and showed the same hyperfine pattern and thermal behavior as observed in tetragonal zirconia obtained by the ceramic route: the two configurations of vacancies around zirconium ions denoted as t1 and t2 forms and their mutual t1 → t2 transformation. While the powder sample exhibited an incipient thermal instability above 1000 °C and underwent completely the t2 form to m–ZrO2 transition during subsequent, gradual cooling below 500 °C, the coating retained the tetragonal phase within the whole temperature range investigated. Hyperfine results suggest that the tetragonal phase stabilization is favored by the highly defective nature of the t1 form and consequently hardened by the availability of oxygen. The PAC derived activation energy for the fast diffusion of the oxygen vacancies inherent to the t2 form was determined as 0.54 ± 0.14 eV.

ZrO2 phase structure in coating films and powders obtained by sol-gel process

1994 ◽  
Vol 3 (3) ◽  
pp. 241-247 ◽  
Author(s):  
R. Caruso ◽  
N. Pellegri ◽  
O. de Sanctis ◽  
M. C. Caracoche ◽  
P. C. Rivas
Keyword(s):  
Phase Structure ◽  
Sol Gel ◽  
Coating Films ◽  
Zro2 Phase ◽  
Sol Gel Process

Thermal analyses of bulk amorphous oxides and silicates of zirconium and hafnium

2002 ◽  
Vol 745 ◽  
Author(s):  
S. V. Ushakov ◽  
C. E. Brown ◽  
A. Navrotsky ◽  
A. Demkov ◽  
C. Wang ◽  
...  
Keyword(s):  
Crystallite Size ◽  
Thermal Analyses ◽  
Sol Gel ◽  
Tetragonal Zirconia ◽  
Interface Energy ◽  
Silica Content ◽  
Scanning Calorimetry ◽  
Amorphous Oxides ◽  
Hafnium Silicate ◽  
Crystallization Onset

ABSTRACTAmorphous pure and Y-doped ZrO2 and HfO2 were prepared by precipitation with ammonia or hydrazine. Amorphous zirconium and hafnium silicates with SiO2 content from 10 to 90 mol % were prepared by sol-gel. Crystallization was studied by differential scanning calorimetry (DSC) at 20 °C/min and crystallite size after crystallization was determined from XRD data. ZrO2 crystallized into the tetragonal phase with ΔH -21 ±2 kJ/mol and HfO2 into the monoclinic phase with ΔH -31 ±2 kJ/mol. Doping with 20 at.% Y decreased crystallite size after crystallization. Crystallization temperatures for pure and Y-doped ZrO2 samples were in the range 420–440 °C. Crystallization temperatures for pure and Y-doped HfO2 samples varied from 470 to 570°C and correlate with surface area. Crystallization onset temperature in silicates increased with silica content from about 650 to 950 °C for ZrO2·SiO2 and from 740 to 1030 °C for HfO2·SiO2. Tetragonal zirconia and hafnia were the only crystalline phases formed below 1100 °C in all zirconium silicates and in hafnium silicates with more than 10 mol% SiO2. Crystallite size after crystallization decreased with increase in silica content. In hafnium silicate, a decrease in HfO2 crystallite size from 5 to 2.5 ±1 nm corresponds to a crystallization enthalpy change from -22 to -15 ±2 kJ/mol. The tetragonal HfO2/amorphous SiO2 interface energy can be calculated from calorimetric data as ∼0.25 J/m2. The critical particle size for the tetragonal to monoclinic transformation of HfO2 in HfO2-SiO2 system is about 6 nm. We predict that tetragonal HfO2 will be stabilized in films thinner than 2 nm.

Phase structure and thermal evolution in coatings and powders obtained by the sol-gel process: Part I. ZrO2−11.3 mol% Y2O3

1997 ◽  
Vol 12 (2) ◽  
pp. 493-500 ◽  
Author(s):  
P. C. Rivas ◽  
M. C. Caracoche ◽  
J. A. Martínez ◽  
A. M. Rodríguez ◽  
R. Caruso ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Thermal Evolution ◽  
Sol Gel ◽  
Correlation Spectroscopy ◽  
Cubic Phase ◽  
Perturbed Angular Correlation Spectroscopy ◽  
Heating And Cooling ◽  
Sol Gel Process ◽  
Fast Movement ◽  
Zirconia Powders

Yttria-stabilized cubic zirconia powders and coatings produced by the sol-gel method have been investigated by Perturbed Angular Correlation Spectroscopy (PAC). Results indicate that the metastable cubic phase is retained during heating and cooling cycles. The hyperfine interaction that describes this cubic phase, once crystallized, exhibits two components in a constant ratio of 4 : 1. The components represent different vacancy configurations. For the fast movement of oxygen vacancies starting at 750 °C, which is reflected by the damping of the hyperfine pattern, an activation energy of 0.96 eV was determined.

Yttria-Doped Zirconia-Hydroxyapatite Composite Coating on Cp-Ti Implants by Biomimetic Method

2012 ◽  
Vol 445 ◽  
pp. 691-696 ◽  
Author(s):  
Aysu Karakas ◽  
A. Binnaz Hazar Yoruc ◽  
Duygu Ceylan Erdogan ◽  
Oktay Elkoca
Keyword(s):  
Tetragonal Phase ◽  
Sol Gel ◽  
Tetragonal Zirconia ◽  
Stress Shielding ◽  
Ceramic Composites ◽  
Composite Powders ◽  
Ti Alloys ◽  
High Fatigue ◽  
Superior Corrosion Resistance ◽  
Cp Ti

Titanium (Ti) and Ti-alloys are often used in dental and orthopedic applications because of their good mechanical properties and biocompatibility. The advantages of Ti and Ti-alloys are its superior corrosion resistance, high fatigue strength and low elastic modulus which reduce stress shielding. Morover biocompatibility of them can be improved coating with bioceramics such as hydroxyapatite (HA) or other ceramic composites. The hydroxyapatite [Ca10(PO4)6(OH)2, H is frequently used as a coating material on the surfaces of Ti-based medical implants to improve the bone fixation and thus the lifetime of the implant is increased. However, the main weakness of HA lies on its poor mechanical strength that makes it unsuitable for load-bearing applications. An attractive way to produce the tougher HA is to use composite powders such as Yttria-Doped Zirconia-Hydroxyapatite (YSZ-HA) consisting of 8 mol% yttria-stabilized tetragonal zirconia (YSZ) so that the apatite phase increases the biocompatibility and zirconia (ZrO2) phase improves the strength. Y2O3addition into zirconia can stabilize the tetragonal phase at room temperature (YSZ) and the tetragonal phase plays a major role to increase the fracture toughness. In the present study yttria-dopped zirconia powders by using ZrO(NO3)2.xH2O and Y(NO3)3.6H2O were produced to synthesize HA-YSZ composites. In accordance with this purpose, at the first step, Ca (NO3)2.4H2O, (NH4)2HPO4and YSZ powders were dissolved in simulated body fluids (SBF) to obtain sol. The gelatin solutions with different concentration were added into sol to provide the gelation. Then the surfaces of Ti implants were soaked in this solution. The coating rate of Ti samples was arranged as 14 cm/s and coated implants were sintered at 900°C. Structural analysis of coated powders was obtained by using XRD. Morphological examinations and coating thickness were investigated by SEM. After the sol-gel solution was dried at 80°C, dried-powder was sintered at 900°C. Sintered powders were analyzed by FT-IR to determine any gelatin residue.

scholarly journals Performance Improvement of ZnSnO Thin-Film Transistors with Low-Temperature Self-Combustion Reaction

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1099
Author(s):  
Ye-Ji Han ◽  
Se Hyeong Lee ◽  
So-Young Bak ◽  
Tae-Hee Han ◽  
Sangwoo Kim ◽  
...  
Keyword(s):  
Thin Film ◽  
Photoelectron Spectroscopy ◽  
Large Scale ◽  
Low Cost ◽  
Thermal Analyses ◽  
Thin Film Transistor ◽  
Sol Gel ◽  
Annealing Temperatures ◽  
Zinc Tin Oxide ◽  
Thermal Limitation

Conventional sol-gel solutions have received significant attention in thin-film transistor (TFT) manufacturing because of their advantages such as simple processing, large-scale applicability, and low cost. However, conventional sol-gel processed zinc tin oxide (ZTO) TFTs have a thermal limitation in that they require high annealing temperatures of more than 500 °C, which are incompatible with most flexible plastic substrates. In this study, to overcome the thermal limitation of conventional sol-gel processed ZTO TFTs, we demonstrated a ZTO TFT that was fabricated at low annealing temperatures of 350 °C using self-combustion. The optimized device exhibited satisfactory performance, with μsat of 4.72 cm2/V∙s, Vth of −1.28 V, SS of 0.86 V/decade, and ION/OFF of 1.70 × 106 at a low annealing temperature of 350 °C for one hour. To compare a conventional sol-gel processed ZTO TFT with the optimized device, thermogravimetric and differential thermal analyses (TG-DTA) and X-ray photoelectron spectroscopy (XPS) were implemented.

Synthesis and Intermolecularly Mediated Assembly of Organic Pigment in Hybrid Coating Films

1998 ◽  
Vol 519 ◽  
Author(s):  
Y. Yan ◽  
Z. Duan ◽  
D.-G. Chen ◽  
S. Ray Chaudhuri
Keyword(s):  
Sol Gel ◽  
Hybrid Coating ◽  
Hypsochromic Shift ◽  
Hybrid Films ◽  
Coating Films ◽  
Organic Pigment ◽  
Inorganic Hybrid ◽  
Matrix Interactions ◽  
Sol Gel Process

AbstractThe insoluble, strongly hydrogen bonded organic pigment of 3,6-bis-(4-chlorphenyl)-l,4- diketopyrrolo [3,4-c] pyrrole was transiently blocked by adding carbamate groups, and consequently incorporated into organic-inorganic hybrid matrices by a sol-gel process. The homo- (pigment-pigment) and hetero-intermolecular (pigment-matrix) interactions were found to control both the assembly and dispersion of pigment molecules in the hybrid coating films. A weaker interaction between matrices and pigment molecules results in aggregation of the carbamate pigment in the methyl-silicate films. A stronger interaction forms a homogenous dispersion and coloration of the phenyl-silicate films. The as-prepared methyl- and phenylsilicate films doped with the organic pigment were distinguished by a morphology change and a blue (hypsochromic) shift in absorption from 550 to 460 nm. Thermal treatment can remove the carbamate groups and in-situ form the organic pigment in the hybrid films.

scholarly journals Thickness-dependent electrocaloric effect in mixed-phase Pb 0.87 Ba 0.1 La 0.02 (Zr 0.6 Sn 0.33 Ti 0.07 )O 3 thin films

2016 ◽  
Vol 374 (2074) ◽  
pp. 20160056 ◽  
Author(s):  
T. M. Correia ◽  
Q. Zhang
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Phase Transitions ◽  
Film Thickness ◽  
Tetragonal Phase ◽  
Sol Gel ◽  
Breakdown Field ◽  
Electrocaloric Effect ◽  
Thickness Increase ◽  
Higher Temperature

Full-perovskite Pb 0.87 Ba 0.1 La 0.02 (Zr 0.6 Sn 0.33 Ti 0.07 )O 3 (PBLZST) thin films were fabricated by a sol–gel method. These revealed both rhombohedral and tetragonal phases, as opposed to the full-tetragonal phase previously reported in ceramics. The fractions of tetragonal and rhombohedral phases are found to be strongly dependent on film thickness. The fraction of tetragonal grains increases with increasing film thickness, as the substrate constraint throughout the film decreases with film thickness. The maximum of the dielectric constant ( ε m ) and the corresponding temperature ( T m ) are thickness-dependent and dictated by the fraction of rhombohedral and tetragonal phase, with ε m reaching a minimum at 400 nm and T m shifting to higher temperature with increasing thickness. With the thickness increase, the breakdown field decreases, but field-induced antiferroelectric–ferroelectric ( E AFE−FE ) and ferroelectric–antiferroelectric ( E FE−AFE ) switch fields increase. The electrocaloric effect increases with increasing film thickness. This article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

Synthesis and Characterizations of Strontium Substituted Hydroxyapatite Thin Films

2010 ◽  
Vol 93-94 ◽  
pp. 231-234
Author(s):  
B. Hongthong ◽  
Satreerat K. Hodak ◽  
Sukkaneste Tungasmita
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Chemical Composition ◽  
Spin Coating ◽  
Phase Structure ◽  
Sol Gel ◽  
Cross Linking ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sol Gel Process

Strontium substituted hydroxyapatite(SrHAp) were fabricated both in the form of powder as reference and thin film by using inorganic precursor reaction. The sol-gel process has been used for the deposition of SrHAp layer on stainless steal 316L substrate by spin coating technique, after that the films were annealed in air at various temperatures. The chemical composition of SrHAp is represented (SrxCa1-x)5(PO4)3OH, where x is equal to 0, 0.5 and 1.0. Investigations of the phase structure of SrHAp were carried out by using X-ray diffraction technique (XRD). The results showed that strontium is incorporated into hydroxyapatite where its substitution for calcium increases in the lattice parameters, and Sr3(PO4)2 can be detected at 900°C. The SEM micrographs showed that SrHAp films exhibited porous structure before develop to a cross-linking structure.

Surface Morphology of Anatase TiO2 Thin Film by Sol-Gel Method

2006 ◽  
Vol 517 ◽  
pp. 135-140 ◽  
Author(s):  
N. Al-Jufairi
Keyword(s):  
Sol Gel ◽  
Titanium Isopropoxide ◽  
Optical Microscope ◽  
Processing Route ◽  
Coating Process ◽  
Coating Films ◽  
Anatase Structure ◽  
Interferometric Technique ◽  
Structure Phase ◽  
Gel Processing

Sol-gel processing route has been used for the production of thin films from titanium isopropoxide (TIP). The surface properties and statistics results have been characterized by AFM; the coating process has been examined using SEM and optical microscope. The structure phase of TiO2 has been analyzed by XRD; the composition of TiO2 has been estimated through EDS; the thickness of film has been measured by polarized microscope in an interferometric technique. The coating films are always crystallined in the anatase structure with circular particles in nanometer size.

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