Yttria Zirconia Research Articles

The Effect of Restoration Thickness on the Fracture Resistance of 5 mol% Yttria-Containing Zirconia Crowns.

To determine what thickness of 5 mol% yttria zirconia (5Y-Z) translucent crowns cemented with different cements and surface treatments would have equivalent fracture resistance as 3 mol% yttria (3Y-Z) crowns. The study included 0.8 mm, 1.0 mm, and 1.2 mm thickness 5Y-Z (Katana UTML) crowns and 0.5 and 1.0 mm thickness 3Y-Z (Katana HT) crowns as controls. The 5Y-Z crowns were divided among three treatment subgroups (n = 10/subgroup): (1) cemented using RMGIC (Rely X Luting Cement), (2) alumina particle-abraded then luted with the same cement, (3) alumina particle-abraded and cemented using a resin cement (Panavia SA Cement Universal). The 3Y-Z controls were alumina particle-abraded then cemented with RMGIC. The specimens were then loaded in compression at 30° until failure. All 5Y-Z crowns (regardless of thickness or surface treatment) had a similar to or higher fracture force than the 0.5 mm 3Y-Z crowns. Only the 1.2 mm 5Y-Z crowns with resin cement showed significantly similar fracture force to the 1 mm 3Y-Z crowns. In order to achieve a similar fracture resistance to 0.5 mm 3Y-Z crowns cemented with RMGIC, 5Y-Z crowns may be as thin as 0.8 mm. To achieve a similar fracture resistance to 1.0 mm 3Y-Z crowns cemented with RMGIC, 5Y-Z crowns must be 1.2 mm and bonded with resin cement.

Wear behavior at high temperature of ZrO2–Y2O3 (YSZ) plasma-sprayed coatings

The wear behavior of two plasma-sprayed zirconia–yttria coatings was studied at high temperatures. Agglomerated and sintered, as well as fused and crushed zirconia–yttria feedstock powders were used to manufacture bimodal and monomodal coatings by atmospheric plasma spraying onto an INCONEL 718 substrate previously coated with a NiCrAlY bond coat. The structure of the coatings was analyzed by SEM on their cross section and surface. The samples were subjected to wear conditions by sliding contact through a ball-on-disk test up to 1000 °C, using an alumina ball 6 mm in diameter as the counterbody, on which a load of 5 N was applied. The samples were rotated during 20000 cycles, reaching a speed of 0.10 m·s−1 at the contact area with the counterbody. The porosity, phase, and mechanical properties were determined before and after wear tests. The results indicate that at 25 °C, both coatings have enough mechanical resistance to withstand the tribological conditions they were exposed to. Therefore, low wear rates were produced by ductile deformation. The tribological conditions became more aggressive as the thermal stresses increased with the test temperature, producing cracking, and detaching particles in the coatings tested at 500 and 750 °C. Consequently, high wear rates related to brittle deformation were obtained. However, the transformation of the amorphous phase to the t′-zirconia phase, produced at 1000 °C, increased the hardness of both coatings and, consequently, their wear resistance; thus, the predominant mechanism of damage was ductile deformation, with wear rates similar to those obtained when the coatings were tested at 25 °C.

Microstructural Property Investigation of LSM-4Sc4YSZ Novel Composite Electrode Prepared Using All-Alkoxide Sol-Gel and Solid-State Reaction Methods for Solid Oxide Electrochemical Cells

Property investigation of co-doped 4 mol% scandia and 4 mol% yttria zirconia (Sc0.08Y0.08Zr0.84O1.92 or 4Sc4YSZ) synthesized via solid-state reaction (SSR) and all-alkoxide sol-gel (SG) method as precursor powders with LSM as composite electrode was conducted. The microstructure and morphology of the precursor powders and resulting LSM-4Sc4YSZ bulk composite electrodes were characterized. The results revealed that the 4Sc4YSZ was successfully synthesized via SG with more distinct cubic phases and finer particles than 4Sc4YSZ prepared via SSR. A more homogeneous and uniform distribution for LSM-4Sc4YSZ SG was also observed with a porosity of 30.65%. Moreover, using electrochemical impedance spectroscopy (EIS), the LSM-4Sc4YSZ SG revealed a total conductivity of 0.158 S/cm at 700 °C with an activation energy of 0.018 eV.

Rh promoted Ni over yttria–zirconia supported catalyst for hydrogen‐rich syngas production through dry reforming of methane

AbstractRh‐promoted YZr‐supported Ni catalyst (5Ni/YZr) is investigated for DRM and characterized with X‐ray diffraction, Raman, infrared spectroscopy, cyclic reduction–oxidation–reduction temperature programmed experiment, thermogravimetry, and transmission electron microscope. Over 5Ni/YZr, some active sites become inactive under the CO2 stream and limit H2 yield to ∼71%. Upon 4 wt% Rh addition over 5Ni/YZr; more than one type of stable active sites (Rh and Ni) generates, moderate basic sites are enhanced, wide ranges of CO2‐interacted surface species (especially bidentate CO2‐adsorbed species) are grown and graphitic carbon proportion over spent catalyst declines. This resulted in 87.35% H2 yield and 86.73% CO yield up to 420 min. 5Ni4Rh/YZr catalyst maintains ∼80% H2 yield at the end of 27 h of DRM reaction.

High carbon-resistant nickel supported on yttria–zirconia catalysts for syngas production by dry reforming of methane: The promoting effect of cesium

Dry reforming of methane (DRM) is a highly researched process for conversion of methane into syngas that consumes the greenhouse gas (CO2). In this work, the promotional effect of cesium on yttria-zirconia-supported nickel catalysts is studied, for the first time, in DRM. Cs loading was varied from 0.5 to 4.0 wt% and fresh materials were characterized by N2 sorption, XRD, TPR, and TEM, while spent catalysts were examined by TEM, Raman spectroscopy, and TGA after catalytic testing. Interestingly, cesium improved carbon resistance of the catalysts. It was shown that addition of up to 1.0 wt% Cs resulted in formation of 13–14 nm nanoparticles in strong interaction with the support, which prevented their sintering during reaction. In this case, hydrogen yield exceeded 75% after 420 min on stream, and this value was higher than those reported in literature for the same loading of other promoters like cerium and barium. However, as the amount of cesium surpassed 1.0 wt%, catalytic performance was lowered, even below that of Cs-free sample and this can be assigned to a possible coverage of active sites by excess cesium. An optimum range of 0.5–1.0 wt% was thus determined for a good performance in dry reforming of methane.

Survey of the mechanical and physical behaviors of yttria-stabilized zirconia from multiple dental laboratories

BackgroundWhen selecting zirconia for a dental restoration, laboratory prescriptions often refer to high strength and high translucency. In this survey, zirconia specimens were ordered from various dental laboratories for posterior (high strength) and anterior (high translucency) clinical indications. The specimens were then tested and evaluated for their mechanical and physical behaviors. MethodsIn a double-blinded manner, 9 laboratories provided 32 specimens from 17 different zirconia blanks, which were tested in the American Dental Association laboratory. Flexural strength tests were performed on standard specimens, and fracture surfaces were examined using both optical and scanning electron microscopy. Chemical composition, Vickers hardness, and absolute transmittance measurements were also performed. ResultsA large scatter in the strength values was observed. The zirconia intended for posterior applications displayed strengths (SD) from 195 through 783 MPa (490 [183] MPa), which overlapped greatly with the strengths (SD) of the zirconia intended for anterior applications, 320 through 768 MPa (581 [136] MPa). However, when the strength values were recalculated on the basis of yttria content, the strengths (SD) were 584 (158) MPa for 3 mol% yttria and 373 (104) MPa for 5 mol% yttria. ConclusionsWhen a prescription was given to dental laboratories to request zirconia on the basis of clinical requirements, there was a large scatter and no consistency in the resulting strength values partly because of mixed use of 3 mol% and 5 mol% yttria zirconia. The 3 mol% materials had much higher strength when the strength values were grouped according to yttria content. Strength was also highly dependent on processing and finishing at the dental laboratories.

Effect of Titanium-Base Abutment Height on Optical Properties of Monolithic Anterior Zirconia Crowns.

The effects of different heights of ti-base abutments on the color of anterior screw-retained zirconia restorations fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM) technologies may affect the optical clinical outcome. The purpose of this study was to measure and compare the color parameters of zirconia crowns in different shades on ti-base abutments. Identical specimens (N = 160) were milled to restore the screw-retained central maxillary incisor crown, using 5% mol yttria zirconia (5Y-TZP). The specimens were designed using computer design software to match 3.5 mm and 5.5-mm ti-base abutments and milled using one CAD-CAM technology. Specimens were divided into four main groups depending on zirconia shade (A1/0, A2/3, A3.5/4 and B2/3) and then assigned to two subgroups according to ti-base height. Color measurements in the CIELab coordinates were made using a spectrophotometer under room-light conditions. Color difference (ΔE*) values were calculated using the CIE76 and CIEDE2000 formula. Within the group of A0/1 and A2/3, for 5.5 mm abutment height, a significant difference was found between the means of colors ∆E00 and ∆Eab (<i>p</i> &amp;lt; 0.01). Using a 5.5 mm-height ti-base abutment may produce a clinically unacceptable outcome (ΔEab &amp;gt; 2) in A1/0 and A2/3 color groups.

Investigation of the Applicability of Y2O3–ZrO2 Spherical Nanoparticles as Tribological Lubricant Additives

Long-term environmental goals will motivate the automotive industry, component suppliers, and lubricating oil developers to reduce the friction of their tribosystems to improve overall efficiency and wear for increased component lifetime. Nanoscale ceramic particles have been shown to form a protective layer on components’ surface that reduces wear rate with its high hardness and chemical resistance. One such ceramic is yttria (Y2O3), which has an excellent anti-wear effect, but due to its rarity it would be extremely expensive to produce engine lubricant made from it. Therefore, part of the yttria is replaced by zirconia (ZrO2) with similar physical properties. The study presents the result of the experimental tribological investigation of nanosized yttria–zirconia ceramic mixture as an engine lubricant additive. Yttria-stabilized zirconia (YSZ) nanoparticle was used as the basis for the ratio of the ceramic mixture, so that the weight ratio of yttria–zirconia in the resulting mixture was determined to be 11:69. After the evaluation of the ball-on-disc tribological measurements, it can be stated that the optimal concentration was 0.4 wt%, which reduced the wear diameter by 30% and the wear volume by 90% at the same coefficient of friction. High-resolution SEM analysis showed a significant amount of zirconia on the surface, but no yttria was found.

Thermal conductivity study of ZrO2-YO1.5-NbO2.5 TBC

The reduction of thermal conductivity provided by the zirconia ceramic for TBC application improves protection of turbine blades during the thermal cycles and the high temperature operations. The TBC is a complex system composed of different layers: a metal substrate, a metallic bond coat, thermally grown oxide (TGO), and ceramic top coat. The present study determined thermal conductivity properties by theoretical calculation of the thermal diffusivity, measured by laser flash technique, at 800 °C and 1250 °C for ZrO2-YO1.5-NbO2.5 (TC) with 14.5, 16.0, and 17.5 mol% equimolar yttria and niobia in zirconia, by CO2 laser on the substrate of titanium. Although microscopy and EDS showed that specific parameters of the laser parameters must be defined to lager thickness of the TBC layers, zirconia co-doped with yttria and niobia promoted a significant reduction of the thermal conductivity by approximately 52 % when compared to zirconia with 7.6 % molar with yttria, currently used in gas turbine engine industry. That TC composition with laser processing could be explored as a candidate thermal insulation material for TBC application.

Biocompatibility of ZrO2 vs. Y-TZP Alloys: Influence of Their Composition and Surface Topography.

The osseointegration of implants is defined as the direct anatomical and functional connection between neoformed living bone and the surface of a supporting implant. The biological compatibility of implants depends on various parameters, such as the nature of the material, chemical composition, surface topography, chemistry and loading, surface treatment, and physical and mechanical properties. In this context, the objective of this study is to evaluate the biocompatibility of rough (Ra = 1 µm) and smooth (Ra = 0 µm) surface conditions of yttria–zirconia (Y-TZP) discs compared to pure zirconia (ZrO2) discs by combining a classical toxicological test, morphological observations by SEM, and a transcriptomic analysis on an in vitro model of human Saos-2 bone cells. Similar cell proliferation rates were observed between ZrO2 and Y-TZP discs and control cells, regardless of the surface topography, at up to 96 h of exposure. Dense cell matting was similarly observed on the surfaces of both materials. Interestingly, only 110 transcripts were differentially expressed across the human transcriptome, consistent with the excellent biocompatibility of Y-TZP reported in the literature. These deregulated transcripts are mainly involved in two pathways, the first being related to “mineral uptake” and the second being the “immune response”. These observations suggest that Y-TZP is an interesting candidate for application in implantology.

39 - Properties of Printed Zirconia Using Suspension Enclosing Projection Stereolithography

To evaluate the feasibility of using suspension enclosing projection stereolithography (SEPS) in printing zirconia dental restorations. Different from most AM processes, this technique is capable of printing overhanging shapes without the need of support structures. A zirconia material (3 M Lava Esthetic, 5%mol zirconia), commonly used to mill zirconia dental restorations, and two experimental printed zirconia groups were analyzed regarding flexural strength, hardness, and microstructure. Thirty-two bar-shaped (n=16) specimens were printed using SEPS from 5% mol yttria zirconia powder (Zpex-Tosoh, Japan) and a photopolymerizable resin from an STL file, at a 70:30, and at a 75:25 ratio. Specimens were cured for 10 minutes, then debinded and sintered. Sixteen specimens were sectioned from zirconia pucks (control) and sintered using a heating, holding, and cooling cycle. Three-point bending test was performed for all 48 specimens using a universal testing machine at 0.5mmm/min cross-head speed. Knoop hardness measurements were performed, using a load of 200 g for 15 s for both groups (n=8). The average of two measurements was recorded. An Independent-Samples Kruskal-Wallis Test was performed to test the flexural strength among the groups. A statistically significant difference was observed for the milled group(p<0.003). The microhardness was not significantly different among groups (p= 0.29, One-way ANOVA). SEPS showed to be a feasible technique to produce zirconia specimens. SEPS produced zirconia showed favorable microhardness properties for dental application. However, SEPS specimens had significantly reduced flexural strength when compared to the control, in particular for the 75% group. Further research is necessary to optimize the debinding and sintering settings when using SESP to print zirconia structures.

Phenomena Occurring upon the Sintering of a Mixture of Yttria-Zirconia Nanometric Powder and Sub-Micrometric Pure Zirconia Powder.

Mixtures of powders essentially differing in their particle morphology and size were applied to prepare polycrystals in a Y2O3-ZrO2 system. An yttria–zirconia solid solution nanometric powder with a Y2O3 concentration of 3.5% was prepared by subjecting co-precipitated gels to hydrothermal treatment at 240 °C. The crystallization occurred in distilled water. The pure zirconia powders composed of elongated and sub-micrometer size particles were also manufactured through the hydrothermal treatment of pure zirconia gel, although in this case, the process took place in the NaOH solution. Mixtures of the two kinds of powder were prepared so as to produce a mean composition corresponding to an yttria concentration of 3 mol%. Compacts of this powder mixture were sintered, and changes in phase composition vs. temperature were studied using X-ray diffraction. The dilatometry measurements revealed the behavior of the powder compact during sintering. The polished surfaces revealed the microstructure of the resulting polycrystal. Additionally, the electron back scattering diffraction technique (EBSD) allowed us to identify symmetry between the observed grains. Hardness, fracture toughness, and mechanical strength measurements were also performed.

Monolithic Zirconia Partial Coverage Restorations: An In Vitro Mastication Simulation Study.

To evaluate the survival rate (fatigue resistance), bonding efficiency and marginal integrity of monolithic zirconia partial and full coverage single restorations adhesively bonded to the tooth structure using air-particle abrasion, a primer with 10-methacryloyloxydecyl dihydrogen phosphate and a composite-resin cement (APC) protocol. Extracted human premolars (N = 32) were randomly divided into four groups of eight specimens each. Premolars were prepared for the following restorations: full crown (group 1, control), mesial-occlusal-distal-facial onlay (MODF, group 2) preserving 2 mm facio-lingual functional cusp width, mesial-occlusal-distal-lingual onlay (MODL, group 3) preserving 2 mm facio-lingual nonfunctional cusp width, mesial-occlusal-distal-buccal-lingual onlay (MODBL, group 4), overlay preparation. All restorations were milled from monolithic 3 mol% yttria (3Y) zirconia blocks (ZirCad, A1 LT, Ivoclar Vivadent) with CAD/CAM software presets at minimum occlusal and axial thicknesses of 1 mm. The intaglio surface of the restorations was air-particle abraded (50 µm Al2 O3 , 2-Bar pressure, 15 s, 10 mm distance) and primed. An adhesive cement system was used to bond the restorations. Each group was subjected to thermomechanical loading for 1.2 million cycles (force = 70 N, 1.4 Hz) with simultaneous thermocycling (5-55°C, 30 s dwell time) using a mastication simulator. All specimens were examined under scanning electron microscope (SEM) analysis (30, 100, and 150×) to evaluate cracks and marginal defects. Fracture of restoration and/or fracture within tooth structure, and debonding were considered modes of failure. One specimen from group 2 debonded at 632,000 cycles. None of the specimens failed due to fracture. SEM analysis at 30× indicated marginal integrity issue of the remaining seven intact specimens of group 2 in the area of antagonist contact. No specimens from group 1, 3, and 4 demonstrated marginal integrity issue at 30×. None of the specimens demonstrated any microcrack at 100× and150×. Due to its fatigue resistance, 3Y-zirconia is a viable option for partial and full coverage single restorations. Following a strict bonding protocol, zirconia demonstrated durable adhesion to the tooth structure. Occlusal contact on restoration margins should be avoided.

Synthesis and Mechanical Properties of Zirconia–Yttria Matrices/Alumina Short Fibre Composites

Yttria tetragonal zirconia polycrystals (YTZP)/alumina short fibre (Al2O3-SF) composites were prepared by wet ball milling. Three different commercial powders of YTZP containing 2, 2.5 and 3 mol% of yttria (denoted as TZ2Y, TZ2.5Y and TZ3YA, respectively) were used as matrices, reinforced with 20 wt% Al2O3-SF. The effect of sintering conditions on the mechanical properties of the composites was studied. XRD and SEM techniques were used for the characterization of the prepared composites. The fracture toughness and hardness were determined by the Vickers indentation technique. The bend strength was measured using a four-point bending test machine. The results showed that both strength and toughness increase with yttria content. The TZ3YA/20 wt% Al2O3-SF composite showed bend strengths up to 760 MPa and fracture toughness of 9.2 MPa√m upon pressureless sintering at 1600 °C. Higher values of the bend strength, up to 855 MPa, were obtained for the post-sintered hipped composites at 1500 °C. The high bend strength and fracture toughness, KIC, result from strong fibre matrix interface. The toughening mechanisms were found to comprise transformation toughening, domain switching and crack deflection toughening. The addition of Al2O3-SF to the matrices of low yttria content was invaluable due to its high monoclinic content upon sintering.

Interactions between zirconia–yttria–tantala thermal barrier oxides and silicate melts

The effects of TaO2.5 additions to Y4Zr3O12 (YZO) on its interactions with calcium-magnesium alumino-silicate (CMAS) melts are investigated. YZO is a candidate material for the protection of novel ZrO2-YO1.5-TaO2.5 based thermal barrier coatings (TBCs) against CMAS attack, but thermochemical considerations dictate that YZO contain TaO2.5 for interfacial compatibility. Oxides based on Y4Zr3-xTaxO12+0.5x (x = =0, 0.7, 1.4) were mixed with various ternary and quinary silicate compositions ranging in Ca:Si ratio from 0.35 to 1.13 and equilibrated at 1300 °C. The results show that all combinations form the desired apatite phase except for the mixture of the higher Ta5+ content with the lowest Ca:Si melt. It is found that the addition of Ta5+ increases the capture of Y3+ by the reprecipitated fluorite, decreasing the amount available to form apatite and eventually suppressing it at low Ca:Si. The effect is ascribed to the attractive interactions between Y3+ and Ta5+ in solid solution, similar to that found in tetragonal zirconia, but with concurrent incorporation of anion vacancies associated with excess Y3+ that stabilize the cubic form. As the Ca2+ content of the melt increases, so does the amount of Ca2+ incorporated in fluorite. The latter also interacts attractively with Ta5+ and leads to a reduction of captured Y3+ in fluorite as the Ca content in the reacting deposit increases. This serves to increase the amount of Y3+available in the melt to form apatite in TBC-CMAS interactions.

Effect of Titania Doping on Structural and Mechanical Properties of NiO/YSZ Anode Materials Sintered by Using Microwave Energy

The current article presents first-hand work on the synthesis of nickel oxide–titania-doped yttria-stabilized zirconia (NiO-YZT) composites of composition 0.40NiO-0.60{[(ZrO2)0.92(Y2O3)0.08]1−x(TiO2)x} with x = 0.00, 0.03, 0.06, 0.09, 0.12 and 0.15 using microwave processing. The composites are prepared by mixed oxide method by taking yttria (Y2O3), titania (TiO2) and monoclinic zirconia (ZrO2) in their stoichiometric ratio and sintered by using conventional and microwave processing techniques. The investigation of prepared composites has been carried out by x-ray diffractometer, scanning electron microscope and Vickers hardness technique to probe the crystal structure, microstructure and mechanical properties. Also, the results obtained are compared for both the conventionally and microwave-sintering routes. It was inferred that the microwave-sintered NiO-YZT showed better results than the conventional samples in terms of greater density, uniform microstructure and better microhardness.

Wide-band flat-gain optical amplifier using Hafnia and zirconia erbium co-doped fibres in double-pass parallel configuration

ABSTRACTA new compact and wide-band erbium-doped fibre amplifier (EDFA) was demonstrated by combining Hafnia-bismuth Erbium co-doped fibre (HB-EDF) and zirconia–yttria–aluminum Erbium co-doped fibre (Zr-EDF) as a hybrid gain medium, in parallel double-pass configuration. The proposed amplifier comprises a 0.5 m long HB-EDF and 4 m long Zr-EDF optimized for C- and L-band operations, respectively. The HB-EDF and Zr-EDF has erbium ion concentration of 12,500 ppm and 2800 ppm, respectively. At -10 dBm input signal, a wide-band flat gain of 15.7 dB is achieved with gain fluctuation of less than 1.5 dB within a wavelength region from 1525 to 1600 nm. Compared to same configuration of HB-EDF and Zr-EDF amplifiers which are using two pieces of HB-EDF and Zr-EDF, respectively with the same total amount of erbium ions, the proposed EDFA with hybrid gain medium provides even better performances in term of flat gain, bandwidth and noise figure.

Evaluation of Microstructure, Phase Composition and Hardness of Alternative Abradable Ceramic Coating Systems Produced by Means of Atmospheric Plasma Spraying

Only a few types of commercially available high temperature ceramic abradable coatings are presented on the market and most of them consist of partially stabilized yttria zirconia with polymer porosity former agent and/or hBN solid lubricant. The basic demand placed on abradable coatings include balance between hardness and erosion resistance. The contribution focuses on the description of microstructure, phase composition and hardness of alternative atmospheric plasma sprayed ceramic abradable coatings deposited from four different experimental powder mixtures: (i) commercial yttria-zirconia + 5 wt. % of experimental BaF2/CaF2, (ii) commercial yttria stabilized zirconia + 10 wt. % of experimental BaF2/CaF2, (iii) R&amp;D powder SrxTiOy and (iv) R&amp;D powder SrxTiOy + 5 wt. % of polyester. The abradable coating systems were of ~ 150 μm thick CoNiCrAlY bond coat and of ~ 800-1000 μm thick ceramic top coat. The microstructure and phase composition of all atmospheric plasma sprayed coating systems were evaluated by the means of scanning electron microscopy and X-ray diffraction techniques. To estimate coatings basic parameters the Rockwell hardness HR15Y was measured.

Stress-induced degradation of 5 mol% yttria–zirconia in water at 300 °C

5 mol% yttria–zirconia ceramic was studied for its use as solid electrolyte in high-temperature pH sensors since this material has interesting mechanical and ion-conducting properties and is available on an industrial scale. However, although its fracture mode in air is transgranular, some batches showed severe intergranular cracking in the working medium, water at 300 °C. In a previous study, it was found that the degradation could be related to the stress caused by the martensitic transformation of intergranular tetragonal precipitates. The aim of present study was to prove this assumption by experiment. To simulate the effect of transforming grain boundary precipitates, a nearly precipitate free material was subjected to an externally applied stress while exposed to 300 °C water. It was found that this also led to degradation by intergranular fracture. This proved the effect of tensile stress, but it also showed that the occurrence of intergranular fracture cannot be attributed solely to the location of the transforming precipitates at the grain boundaries. In an attempt to find the cause of the stress-induced intergranular fracture, 8 mol% yttria–zirconia was tested as well but this material showed only transgranular fracture. As a possible explanation, it is suggested that the occurrence of intergranular fracture in the 5 mol% yttria ceramic is not a property of the pure yttria–zirconia system but that sintering additives or impurities, segregated at the grain boundaries, could be the cause. However, examination of such segregation was not foreseen in the present study. Nevertheless, based on the present results it is thought that it should be possible to reduce degradation by a strict decrease of the amount and size of the intergranular tetragonal precipitates.

An efficient L-band Zirconia Yttria Aluminum Erbium co-doped fiber amplifier with 1480nm pumping

The optical amplification performance of the proposed Zirconia Yttria Aluminum Erbium co-doped fiber (Zr-EDF) was compared for two different pumping schemes; 1480 and 980[Formula: see text]nm. An efficient [Formula: see text]-band amplifier was achieved using 3[Formula: see text]m length of Zr-EDF while 1480[Formula: see text]nm pumping is found to provide higher attainable gain and better noise figure as compared to 980[Formula: see text]nm pumping. At a pumping wavelength of 1480[Formula: see text]nm and an input signal power of [Formula: see text]10[Formula: see text]dBm, the proposed amplifier provides a relatively flat-gain of about 13.3[Formula: see text]and 17.3[Formula: see text]dB with single-pass and double-pass configuration, respectively, where the gain variation was less than 1[Formula: see text]dB within a wavelength region of 1560–1600[Formula: see text]nm. The noise figures of the proposed Zr-EDFA were maintained below 8 and 14.5[Formula: see text]dB for single-pass and double-pass arrangement, respectively, within the flat-gain region. Compared to the conventional amplifier configured with silica based erbium-doped fiber amplifier, the proposed Zr-EDF-based amplifier achieves a higher and flatter gain and lower noise figure at [Formula: see text]-band region even though it uses a shorter length of gain medium.