Textured Yttria-stabilized Zirconia Research Articles

Effect of environmental dust particles on laser textured yttria-stabilized zirconia surface in humid air ambient

Zirconium nitride is used as a selective surface for concentrated solar heating applications and one of the methods to form a zirconium nitride is texturing of zirconia surface by a high intensity laser beam under high pressure nitrogen gas environment. Laser texturing also provides hydrophobic surface characteristics via forming micro/nano pillars at the surface; however, environmental dust settlement on textured surface influences the surface characteristics significantly. In the present study, laser texturing of zirconia surface and effects of the dust particles on the textured surface in a humid air ambient are investigated. Analytical tools are used to assess the morphological changes on the laser textured surface prior and after the dust settlement in the humid air ambient. It is found that laser textured surface has hydrophobic characteristics. The mud formed during condensate of water on the dust particles alters the characteristics of the laser textured surface. The tangential force required to remove the dry mud from the textured surface remains high; in which case, the dried liquid solution at the mud-textured surface interface is responsible for the strong adhesion of the dry mud on the textured surface. The textured surface becomes hydrophilic after the dry mud was removed from the surface by a desalinated water jet.

Dual ion beam assisted magnetron deposition of biaxially textured YSZ and YBCO/YSZ thin films

Abstract Biaxially textured yttria stabilized zirconia (YSZ) thin films were deposited on polished hastelloy and silicon substrates using ion beam assisted deposition (IBAD). The IBAD apparatus includes a planar magnetron fitted with a crystalline YSZ target to provide the film-forming species, and two Kaufman-type ion beam sources which provide Ar+ ions for bombarding the film during growth. The two ion beam sources were mounted symmetrically at 55° angles to the substrate plane normal, making 110° angle between them. Textured YSZ films were deposited under three different IBAD conditions: (a) films were bombarded by a single ion beam source (SIBAD), (b) films were bombarded by a single ion beam source for a time alternating from the two symmetric directions (AIBAD), and (c) by dual ion beam assisted deposition (DIBAD) where the film was bombarded simultaneously from the two symmetric directions. The X-ray φ-scan results indicate that DIBAD followed by epitaxial growth of YSZ produced the highest degree of biaxial texture in YSZ films. Superconducting yttrium barium copper oxide (YBCO) films deposited on highly textured DIBAD YSZ films had φ-scan full width at half maximum of 7.1° and 5.5° for hastelloy and silicon substrates, respectively.

Reactive magnetron sputtering of uniform yttria-stabilized zirconia coatings in an industrial setup

Yttria-stabilized zirconia (YSZ) thin films were deposited by reactive magnetron sputtering in an industrial scale setup on silicon wafers as well as commercial NiO-YSZ fuel cell anodes. The texture, morphology, and composition of the deposited films were investigated as a function of deposition parameters. Homogeneous coatings could be deposited over large areas within the coating zone, which is important for industrial applications. The use of substrate bias during film growth was identified as a key parameter to promote less columnar coatings and made it possible to tailor the texture of films deposited on Si. Bias voltages≤−40V resulted in highly <200> textured YSZ films, intermediate bias voltages of −50V to −70V in <220> textured films and high bias voltages (≥−90V) in a mixed orientation. In contrast, films grown on NiO-YSZ were seen to be randomly orientated when deposited at substrate bias voltages≤−30V. When bias was further increased the film took over the orientation of underlying substrate due to substrate template effects.

Nanoscale effects on the ionic conductivity in highly textured YSZ thin films

The electrical conductivity of highly textured Yttria Stabilized Zirconia (YSZ) thin films deposited onto a MgO substrate can be enhanced significantly at thickness < 60 nm. The structure of these films is characterized by a negligible dislocation network coupled with only one film/substrate interface, which results in the absence of blocking effects. The in-plane conductivity measurements as a function of temperature and film thickness reveal a nanoscale effect with exceptionally high ionic conductivity for film thickness < 60 nm. The observed behavior is attributed to a significant contribution from interface conductivity with decrease in the film thickness. The analysis of presented results was performed using the rule of mixtures model and the lattice (grain) and interface related conductivities were separated. It was estimated that the thickness of interface layer is about 1.6 nm and interfacial conductivity is over three orders of magnitude larger than the lattice related conductivity, which illustrated the tremendous potential of nanoscaled materials.

Effects of neutralizers on the crystal orientation of YSZ films grown by using ion beam sputtering

Yttria-stabilized zirconia (YSZ) thin films, having cube-on-cube epitaxial relationship with Si, have been often fabricated by using ion beam sputtering for various buffer layer applications. Since the charging of Ar+ ion on targets is detrimental to the sputtering, an appropriate neutralizer eliminating the charging of YSZ target should be used in the sputtering. In order to identify optimum neutralizer for the YSZ film growth, various neutralizers, such as tungsten (W), thoria-coated Ir and zirconium (Zr) have been tried for the ion beam sputtering of YSZ film at 800°C. For the evaluation of the crystallinity and texture of YSZ films, X-ray diffraction analysis and high-resolution electron microscopy (HREM) were performed. The YSZ films grown with W neutralizer exhibited a texture with (1 1 1) preferred orientation. In addition, W particles of a 2–3 nm in diameter were often observed at the interface between the YSZ and Si substrate. Evaporated W during the deposition process was suggested to prevent the formation of (0 0 2) textured grain. The YSZ films with thoria-coated Ir and Zr neutralizers, however, revealed (0 0 2) preferred orientation without any precipitations present at the interface. Oxygen pressure with Zr neutralizer could increase effectively the (0 0 2) texture. Present results suggest that a Zr neutralizer is the best neutralizer for the growth of (0 0 2) textured YSZ thin film.

Effects of neutralizers on the crystal orientation of YSZ films grown by using ion beam sputtering

Yttria-stabilized zirconia (YSZ) thin films, having cube-on-cube epitaxial relationship with Si, have been often fabricated by using ion beam sputtering for various buffer layer applications. Since the charging of Ar + ion on targets is detrimental to the sputtering, an appropriate neutralizer eliminating the charging of YSZ target should be used in the sputtering. In order to identify optimum neutralizer for the YSZ film growth, various neutralizers, such as tungsten (W), thoria-coated Ir and zirconium (Zr) have been tried for the ion beam sputtering of YSZ film at 800°C. For the evaluation of the crystallinity and texture of YSZ films, X-ray diffraction analysis and high-resolution electron microscopy (HREM) were performed. The YSZ films grown with W neutralizer exhibited a texture with (1 1 1) preferred orientation. In addition, W particles of a 2–3 nm in diameter were often observed at the interface between the YSZ and Si substrate. Evaporated W during the deposition process was suggested to prevent the formation of (0 0 2) textured grain. The YSZ films with thoria-coated Ir and Zr neutralizers, however, revealed (0 0 2) preferred orientation without any precipitations present at the interface. Oxygen pressure with Zr neutralizer could increase effectively the (0 0 2) texture. Present results suggest that a Zr neutralizer is the best neutralizer for the growth of (0 0 2) textured YSZ thin film.

Growth of highly textured yttria-stabilized zirconia thin film by reactive magnetron sputtering

Growth of highly textured yttria-stabilized zirconia thin film by reactive magnetron sputtering

Growth of Biaxially Textured Yttria-Stabilized Zirconia Thin Films on Si(111) Substrate by Ion Beam Assisted Deposition

The (001) oriented yttria-stabilized zirconia (YSZ) films with in-plane biaxial texture have been deposited on Si(111) substrates by ion beam assisted deposition at ambient temperature. The effects of ion/atom arrival rate ratio (R=(Ar++O2+)/ZrO2) and incident angle of bombarding ion beam on the film texture development were investigated. It was found that the in-plane biaxial texture of the films was improved gradually with increasing ion/atom arrival rate ratio R up to a critical value 1.9, but it was degraded with the further increase of R. The optimal in-plane biaxial texture, whose full width at half maximum of the (111) φ-scan spectrum is 14°, can be obtained at R=1.9 and incident angle of 55°. For a fixed R, the optimal crystallinity and in-plane biaxial alignment of the YSZ films did not appear at the same incident angle and showed an opposite variation with the change of the incident angle from 51° to 55°. C-axis alignment (perpendicular to substrate surface) does not show any substantial variation with the change of incident angle within the range of 47° - 56°.

In-plane aligned YBCO film on textured YSZ buffer layer deposited on NiCr alloy tape by laser ablation with only O+ ion beam assistance

High critical current density and in-plane aligned YBa2Cu3O7-x (YBCO) film on a textured yttria-stabilized zirconia (YSZ) buffer layer deposited on NiCr alloy (Hastelloy c-275) tape by laser ablation with only O+ ion beam assistance was fabricated. The values of the x-ray phi-scan full width at half-maximum (FWHM) for YSZ(202) and YBCO(103) are 18° and 11°, respectively. The critical current density of YBCO film is 7.9 × 105 A cm-2 at liquid nitrogen temperature and zero field, and its critical temperature is 90 K.

High-T/sub c/ coated conductors-performance of meter-long YBCO/IBAD flexible tapes

One meter long tapes based on 50-100 /spl mu/m thick by 1 cm wide nickel alloy substrates have been coated in a continuous process with a textured yttria-stabilized zirconia layer by ion beam-assisted deposition, followed by a 1-2 /spl mu/m thick layer of YBCO by pulsed laser deposition. The best result to date is a tape with a critical current (I/sub c/) at 75 K of 96 A over an 87 cm measurement length. The overall critical current density and engineering current density are 1 MA/cm/sup 2/ and 10 kA/cm/sup 2/, respectively. Using a special probe, individual I-V curves were generated for each centimeter of tape length in order to investigate longitudinal uniformity of the transport properties: the highest and lowest I/sub c/ values fall within a range of /spl plusmn/25%.

Study on the growth of biaxially aligned yttria-stabilized zirconia films during ion beam assisted deposition

(001)-oriented and in-plane aligned yttria-stabilized zirconia (YSZ) thin films were synthesized on Ni–Cr alloy substrates by ion beam assisted deposition. It was found that it is not the 〈111〉 axial channel but the {110} plane channel that will always follow the direction of the bombarding ion beam and will result in the in-plane aligned structure of the YSZ films. At 55° incident angle, the bombarding ion beam is in the {110} plane channel and the 〈111〉 axial channel simultaneously; this produces the optimal biaxial alignment of YSZ films. On YSZ single crystalline substrates or textured YSZ layers, growth of YSZ films will not be controlled by the bombarding ion beam; rather, but the films continue to grow along the lattice orientation of the substrate. The formation of the biaxial alignment is an evolutionally selected process by ion beam selective bombardment. YSZ grains of (001) orientation are resputtered less than other oriented grains under ion beam bombardment, which causes the (001) orientation to emerge from initial random orientations evolutionally. About a 1000 Å-M20 thickness is needed to develop the alignment. The roughness of the substrate has no obvious influence on the alignment within several hundred Å. Increasing the substrate temperature tends to reduce the (001) orientation and to promote the (111) orientation along the substrate normal. Postannealing of the YSZ films fabricated at ambient temperature can improve the crystalline structure.

Enhancement of critical current density in Tl 2Ba 2CaCu 2O y superconducting thin film on polycrystalline Al 2O 3 substrates using textured YSZ buffer layers

Tl 2Ba 2CaCu 2O y superconducting thin films on polycrystalline Al 2O 3 substrates with and without textured yttria-stabilized-zirconia(YSZ) or CeO 2/YSZ buffer layers were fabricated. Ion beam-assisted laser deposition was used to obtain the textured YSZ buffer layers. The Tl 2Ba 2CaCu 2O y thin films grown on the YSZ buffer layers were highly c-axis oriented with respect to the film surface and strongly in plane textured. The zero resistance temperature of these films was 100–108K. The critical current density (J c) of the films grown on the YSZ buffer layers was 10 5A/cm 2. J c of the films grown on the CeO 2/YSZ buffer layer or on Al 2O 3 substrates directly was less than 10 4A/cm 2.

Tl 2Ba 2CaCu 2O y superconducting thin films on polycrystalline Al 2O 3 substrates with textured YSZ buffer layers

We report for the first time the successful fabrication of Tl 2Ba 2CaCu 2O y superconducting thin films on polycrystalline Al 2O 3 substrates using yttria-stabilized-zirconia (YSZ) buffer layers. Ion beam-assisted laser deposition was used to obtain the textured YSZ buffer layers. The Tl 2Ba 2CaCu 2O y thin films were shiny, highly c-axis oriented with respect to the film surface and strongly in plane textured. The zero resistance temperature of these films was as high as 108 K with a critical current density of ∼ 10 5 A/cm 2 at 77 K.

Preparation of in-plane textured buffer layers for YBa2Cu3Oy film growth by modified bias sputtering

Abstract A modified bias sputtering technique has been proposed to grow in-plane textured yttria-stabilized zirconia buffer layers on polycrystalline metallic substrates for deposition of YBa2Cu3Oy films. The principle of developing an in-plane texturing by this technique is basically the same as that of ion beam assisted deposition; an in-plane texturing occurs by off-normal ion beam bombardment because of the higher sputtering yields of all orientations other than the channelling direction. In our process, however, a flux of energetic particles impinging on the growing film is generated using specially devised negatively biased electrodes installed in a magnetron sputtering system instead of a separate ion-source in IBAD. So far an X-ray phi-scan width of 18° was attained for YSZ films on Hastelloy tapes. Epitaxial YBCO films grown on these buffer layers using pulsed laser deposition showed the Jc’s exceeding 105 A cm−2 (77 K, 0 T). In this paper, we present variation of the bias sputtering technique also used to obtain the textured films on large area substrates. Although the proposed process offers a very convenient method to grow textured films, more efforts must be made to increase growth rates of the films (currently ∽0.1 nm s−1) for large-scale applications of YBCO films.

Properties of YBa2Cu3O7−δ thick films on flexible buffered metallic substrates

We report superconducting and mechanical properties of YBa2Cu3O7−δ (YBCO) thick films on Ni-based alloys with a textured yttria-stabilized zirconia (YSZ) buffer layer. The YBCO and YSZ layers were deposited by pulsed laser deposition and ion beam assisted deposition, respectively. It was found that the transport critical current density (Jc) correlates very well with the YBCO mosaic spread. Jc over 1×10 6 A/cm2 at 75 K and ∼1×107 A/cm2 at 4 K were obtained in the 1-μm thick YBCO films. Zero field critical current of 120 amps at 75 K was obtained in a 2-μm-thick and 1-cm-wide YBCO film. Angular dependence measurement revealed Jc peaks for both H∥c and H∥a-b. The peak for H∥c implies additional pinning due to defects such as small angle grain boundaries or twin boundaries. Bending tests at 75 K showed that the YBCO thick films on the metallic substrates could sustain a strain of 0.4% and over 1% for tension and compression, respectively.

In situ single chamber laser processing of YBa2Cu3O7−δ superconducting thin films on Si (100) with yttria-stabilized zirconia buffer layers

In situ pulsed excimer laser processing of high Tc YBa2Cu3O7−δ films on Si (100) substrates with yttria-stabilized zirconia (YSZ) buffer layers, has been carried out for the first time using a multitarget deposition system. Both YSZ and YBa2Cu3O7−δ layers were deposited sequentially using a KrF excimer laser (λ=248 nm) at substrate temperature of 650 °C. The morphology and structure of the buffer layers and YBa2Cu3O7−δ films were determined using x-ray diffraction and transmission electron microscopy techniques. The superconducting transition temperature Tc (onset) of 90 K and Tc0 (zero resistance) of 82 K were achieved for YBa2Cu3O7−δ thin films on Si with YSZ buffer layers. An interesting result of this study was that good quality, highly textured YBa2Cu3O7−δ films with the c axis perpendicular to the substrate could be grown on single crystal as well as polycrystalline textured YSZ layers deposited on silicon substrates.