Synthesis of the mineral geikielite MgTiO3

The preparation of pure geikielite, MgTiO₃, is carried out by precipitation with NaOH solution at pH 12 from solutions Ti⁴⁺/Mg²⁺ in molar ratio 1/1 M and calcination of the precipitate at 600°C in a dynamic atmosphere: heating rate 300°Ch^–1.At room temperature and a 1 KHz of frequency the dielectric constant () and the electric resistivity () were measured. The values were = 1 5.0 and = 1.1×10¹⁰ cm^–1.     

Influence of poling conditions on the piezoelectric properties of PZT ceramics

The influence of the poling temperature, the poling electric field, the poling time and the distance between electrodes on the dielectric constant _r and the electro-mechanical coupling factor k_r of PZT were investigated using a statistical analysis method. Interactions between various factors affecting _r and k_r parameters were found particularly, with regard to the poling temperature. The k_r value of PZT is influenced more by the absolute voltage than by the applied electric field strength.     

Dielectric and pyroelectric properties of PZFNT/PZT bimorph thin films

Pyroelectric Pb_1,1(Zr_0.58Fe_0.2Nb_0.2Ti_0.02)O₃/Pb_1.1(Zr_0.9Ti_0.1)O₃ (PZFNT/PZT) bimorph thin films are processed via a modified sol-gel method on highly textured (1 1 1)Pt/Ti/SiO₂/Si substrates. XRD and SEM investigations show full pyrochlore to perovskite phase transformation after annealing at 750 °C. XPS depth profiling reveals diffusion of Fe leading to a broad transition layer. The PZT 90/10 bottom layer was shown to be effective for dielectric permittivity control of the bimorph structure. The small signal dielectric constant, , was determined as 580 at 10 kHz. The temperature dependence of is shown to exhibit a single maximum at approximately 195 °C. The C–V characteristics of the bimorph structure show the typical behavior of ferroelectric perovskites. These results are attributed to microstructural effects, particularly the presence of a broad transition layer. The pyroelectric properties are reported in the temperature range from 20 to 60 °C and compared to monomorph PZT and PZFNT films. It is shown that the bimorph thin film has higher pyroelectric coefficient and detectivity than the constituent monomorph films.     

Preparation and Characterization of Epitaxial-Grown Ba0.65Sr0.35TiO3 Thin Films by the Sol-Gel Process on Pt/MgO Substrates

Epitaxial-grown barium-strontium-titanate (BST, Ba_0.65Sr_0.35TiO₃) thin films have been successfully deposited on Pt/MgO (100) substrates using sol-gel techniques. Crack-free 350-nm-thick films were fabricated using a multilayer spinning technique and calcination at 650°C in oxygen for 1 hr. The X-ray diffraction pattern showed that (001) planes of BST films were mainly laid parallel to Pt (100) and MgO (100). The dielectric constant and dissipation factor for BST thin films at a frequency of 10 kHz were 480 and 0.02, respectively. The results of the temperature-dependence of the dielectric constant and dissipation factor showed that sol-gel–derived BST films had Curie temperatures of about 35°C and diffused ferroelectric phase transition characteristics. The leakage current density through the BST films was about 2.75 × 10^–7 A/cm² at an applied voltage of 3 V. The BST films exhibited a well-saturated ferroelectric hysteresis loop with remnant polarization P _r = 2.8 C/cm² and coercive field E _c = 52 kV/cm.     

The effect of PbO content on a modified lead titanate ceramic

Modified lead titanate ceramics were prepared from batches with compositions Pb_xCa_0.30Ti₀₉₄ (Co_1/2W_1/2)_0.06O_23+x (x = 0.67, 0.68, 0.69, 0.70, 0.71 and 0.72) with 1 mol % MnO to determine the effect of PbO content on the dielectric and piezoelectric properties. An increase in PbO content increased the grain size and reduced the planar coupling factork _p. The dielectric constant _T ³³ /₀ and the piezoelectric constantd ₃₃ reached a maximum for a ceramic made from a batch with stoichiometric PbO content (x = 0.70).     

Characterization of (Pb,La) TiO3 thin films prepared by the sol-gel method

Pb_(1–1.5x)La_xTiO₃ thin films were synthesized by the sol-gel spin-coating technique. The films became crystallized when the spin-coated films were annealed at 600 °C and at higher temperature, and became amorphous when annealed at 550 °C. The breakdown voltage, V _B, was recorded at around 30 V for 600–650 °C annealed films and varied only slightly with the composition. The V _B value of the amorphous films was observed to be higher than that of the crystalline films. The ferroelectric properties of both the amorphous and crystalline films were found to be similar. The dielectric constant, charge storage density and optical index of refraction of the films were _r =5–20, Q _c=0.12–0.54 C cm^–2 and n=1.6–2.3, respectively. They all increased moderately with La³⁺ content in the films. One possible reason why the ferroelectric properties are not modified as the amorphous films crystallize, may be that the octahedra are equilateral, whether the films are amorphous or crystalline. Additionally, a possible cause which lowers the breakdown voltage in crystalline film, is the formation of lead vacancies due to lead loss. The electrical properties of films coated on bare silicon become significantly lowered due to interdiffusion between films and substrate. The diffusion of Si⁴⁺ ions into-the films can be prevented by coating SrTiO₃ on the silicon substrate as a buffer layer. The charge storage capacity consequently becomes substantially enhanced.     

High-field electrical conduction in m Hgl2

The electrical and dielectric properties of illuminated Hgl₂ were studied at room temperature under various a.c.-signal amplitudes in the frequency range 1 Hz to 10 kHz. Below 40 H, We real part of the dielectric constant, ,was found to vag slightly with voltege for low electric fields (E < 10³V cm^–1, above which it showed a steady increase with the applied voltage. At higher frequencies, no voltage dependence of (or the geometrical capacitance) of the crystal was observed. On the other hand, the imaginary part of the dielectric constant, or the a.c. conductivity, (=_o) was found to decrease considerably with the applied voltage forE < 10³V cm^–1 at all frequencies. For higher fields (E > 10³V cm^–1), exp [C(E/)^1/2], whereC is e constant. Above 40 Hz, this variation was in good agreement with the behaviour of the bulk, resistance of the crystal. Such behaviour is discussed in the view of Richardnon-Schottky and Poole-Frenkel conduction mechanisms, which seem to be operative in Hgl₂ at room temperature.     

Study on the properties of a nanocrystal and polymer composite PbTiO3/PEK-c film with optical anisotropy

Composite thin films of PbTiO₃ nanocrystals and PEK-c polymer for applications in nonlinear optical devices were prepared by spin coating. The size of PbTiO₃ nanocrystals was estimated to be 30–40 nm. The microstructure of PbTiO₃/PEK-c composite polymer film before and after poling was analyzed by X-ray diffraction, which show that this film is c axis-orientated. The poled composite film displayed the refractive index anisotropy. In this sample the TE- and TM-indices differences are found to be 0.02945 for 633 nm and 0.03915 for 414 nm. The electro-optic coefficient ₃₃ of poled composite film was measured to be 12.89 pm V^–1 at 633 nm by the transmission technique. The dielectric constant of it at 100 KHz under room temperature was determined to be 7.32. The figure of merit F ₂ was estimated to be 492. In addition, a relaxation process was observed in the time range of 28 days and the relaxation time constant was calculated to be 2393 min.     

Pb(Zr0.52Ti0.48)O3/TiNi multilayered heterostructures on Si substrates for smart systems

Ferroelectric/shape memory alloy thin film multilayered heterostructures possess both sensing and actuating functions and are considered to be smart. In this article, Pb(Zr_0.52Ti_0.48)O₃ (PZT) ferroelectric thin films and Ti-riched TiNi shape memory alloy thin films have been deposited on Si and SiO₂/Si substrates in the 400-600 °C temperature range by pulsed laser deposition technique. Deposition processing, microstructure and surface morphology of these films are described. The TiNi films deposited at 500 °C had an austenitic B2 structure with preferred (110) orientation. The surfaces of the films were very smooth with the root-mean-square roughness on a unit cell level. The structure of the TiNi films had a significant influence on that of the subsequently deposited PZT films. The single B2 austenite phase of the TiNi favored the growth of perovskite PZT films. The PZT/TiNi heterostructures with the PZT and TiNi films respectively deposited at 600 and 500 °C exhibited a polarization-electric field hysteresis behavior with a leakage current of about 2 × 10^− 6 A/cm².     

Viscoelastic-plastic behaviour with mean strain changes in polypropylene

The stress-strain curves and stress-relaxation curves of polypropylene are obtained by using a closed-loop, electrohydraulic, servo-controlled testing machine. Effects of mean strain changes on deformation behaviour are examined in a tension-compression mode under strain control at room temperature (18–23 °C). The hysteresis loops of three mean strains show a steady-state response from the stress-strain curves at a strain rate of 1 × 10^–3 s^–1 at a strain width of 5%, at a number of cycles of N=50 and at three mean strains (_m=0, + 1.0 and + 2.0%). The drop of stress at the mean strain of _m= -1.0% is larger in magnitude than that at _m=+1.0%; this is caused by the higher stress level at _m=- 1.0% as compared with the stress level at _m=+1.0%. From the results of stress amplitude and the stress drop behaviour, the magnitude of stress drop is hardly affected by the mean strain.     

Improved dielectric properties of chemical solution derived Pb0.5Sr0.5TiO3 thin films by a layer-by-layer annealing method

Pb_0.5Sr_0.5TiO₃ thin films were prepared on Pt/TiO₂/SiO₂/Si and LaNiO₃ (LNO)/Si substrates by using chemical solution deposition technique, and a layer-by-layer annealing method was used in an attempt to improve the dielectric properties of the thin films. The structure, dielectric, and ferroelectric properties of the thin films were investigated. Improved dielectric properties of the thin films were clearly confirmed: the dielectric constant and dielectric loss for the films on Pt/TiO₂/SiO₂/Si substrates annealed at 650 °C were 1064 and 0.027, respectively, at 1 kHz, with a dielectric tunability of more than 50%; similarly, the films prepared on LNO/Si substrates, showed a high dielectric constant of 1280 and a low dielectric loss of 0.023, at 1 kHz. P-E hysteresis loop measurements indicated that the remanent polarization and coercive field for the films on Pt/TiO₂/SiO₂/Si substrates annealed at 650 °C were 15.7 μC/cm² and 51 kV/cm, respectively.     

Problem of measuring the thermophysical characteristics of thin resistive and dielectric films

We consider the theoretical and experimental possibilities of determining a complex of thermophysical characteristics of thin films on a substrate, on the basis of a nonstationary method with boundary conditions of the fourth kind.Notation time - x coordinate perpendicular to the film surface - ₂, ₀, ₁ coefficients of thermal activity (=/a) of the substrate, the film, and the secpnd body - T₀₀ initial temperature of the film-substrate system - T₁₀ initial temperature of the second body - =T₁₀ – T₀₀ T ₀ ⁰ temperature at the boundary after contact as 0 - T ₀ ^t8 temperature at the boundary after contact as Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 98–101, January, 1982.     

The dielectric properties of aluminium nitride substrates for microelectronics packaging

The dielectric behaviour of sintered polycrystalline aluminium nitride substrates has been examined over the frequency range 500 Hz to 10 MHz and correlated with composition and microstructure. For pure, white AlN at 20 ° C both the permittivity () and dielectric loss () are frequency independent giving = 9.2±0.05 and tan = (2.1±0.1) × 10^–3. The permittivity is less than for pure alumina substrates ( = 10.2) but tan compares favourably, with that (1.4 × 10^–3) of alumina, which though used more widely has a thermal conductivity some eight times less than that of AlN. The addition of impurities, particularly iron, to give opaque black AlN causes large, frequency dependent increases in ; at 500 Hz the loss is seven times that of pure white AlN and is two times greater above 100 kHz. The temperature coefficient of permittivity [( – 1)( + 2)]^–1 [/T]_p between –180 and +180 ° C for pure white AlN is 1.05×10^–5 K^–1 which is similar to the value of 9×10^–6 K^–1 for pure Al₂O₃. For impure black AlN the coefficient below 20 ° C is the same but above 20 ° C there is a rapid, non-linear increase of with temperature. Below 180 ° C for pure white AlN and 20 ° C for impure black AlN the values of temperature coefficient are frequency independent at least up to 200 kHz.     

Electrical properties of non c-axis oriented SrBi2(Ta0.95V0.05)2O9 thin films

Pulsed laser deposition technique was used to grow off c-axis oriented SrBi₂(Ta_0.95V_0.05)₂O₉ (SBTV) ferroelectric thin films. X-ray diffraction studies revealed the c-axis suppression in the films grown at lower substrate temperature (350°C) followed by annealing at higher temperatures (650°C). In-plane lattice parameters of the films were decreased with increase in annealing temperature. SBTV films annealed at 750°C exhibited enhanced ferroelectric properties with remanent polarization (2P _r) of 31.5 C/cm² and coercive field (E _c) of 157 kV/cm. The dielectric permmitivity of the films increased with increase in annealing temperature and it was attributed to the grain size dependence. The films annealed at 750°C showed maximum value of dielectric permittivity 172 with a tangential loss of 0.1, at 100 kHz. Higher value of dissipation factor at lower annealing temperature is explained in terms of space charge accumulation at grain boundaries. The leakage current densities of the films follow ohmic behavior at low field regime and space charge limited current dominates at higher fields.     

Structural and electrical characteristics of chemical solution derived (Bi3.2La0.4Nd0.4)Ti3O12 thin films

(Bi_3.2La_0.4Nd_0.4)Ti₃O₁₂ (BLNT) thin films were prepared on Pt/Ti/SiO₂/Si substrates by using chemical solution deposition technique, and the effects of annealing temperatures in the range of 550-750 °C on structure and electrical properties of the thin films were investigated. X-ray diffraction analysis shows that the thin films have a bismuth-layered perovskite structure with preferred (117) orientation. The surface morphology observation by field-emission scanning electron microscopy confirms that films are dense and smooth with uniformly distributed grains. The grain size of the thin films increases with increasing annealing temperature; meanwhile, the structural distortion of the thin films also increases. It was demonstrated that the thin films show good electrical properties. The dielectric constant and dielectric loss are 191 and 0.028, respectively, at 10 kHz for the thin film annealed at 600 °C, and the 2Pr value of the thin film annealed at 700 °C is 20.5 μC/cm² at an electric field of 500 kV/cm.     

Role of La0.5Sr0.5CoO3 template layers on dielectric and electrical properties of pulsed-laser ablated Pb(Nb2/3Mg1/3)O3-PbTiO3 thin films

Relaxor ferroelectric thin films of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) deposited on platinized silicon substrates with and without template layers were studied. Perovskite phase (80% by volume) was obtained through proper selection of the processing conditions on bare Pt/Ti/SiO₂/Si substrates. The films were initially grown at 300 °C using pulsed-laser ablation and subsequently annealed in a rapid thermal annealing furnace in the temperature range of 750-850 °C to induce crystallization. Comparison of microstructure of the films annealed at different temperatures showed change in perovskite phase formation and grain size etc. Results from compositional analysis of the films revealed that the films initially possessed high content of lead percentage, which subsequently decreased after annealing at temperature 750-850 °C. Films with highest perovskite content were found to form at 820-840 °C on Pt substrates where the Pb content was near stoichiometric. Further improvement in the formation of perovskite PMN-PT phase was obtained by using buffer layers of La_0.5Sr_0.5CoO₃ (LSCO) on the Pt substrate. This resulted 100% perovskite phase formation in the films deposited at 650 °C. Dielectric studies on the PMN-PT films with LSCO template layers showed high values of relative dielectric constant (3800) with a loss factor (tan δ) of 0.035 at a frequency of 1 kHz at room temperature.     

Damping properties of epoxy-based composite embedded with sol–gel-derived Pb(Zr<Subscript>0.53</Subscript>Ti<Subscript>0.47</Subscript>)O<Subscript>3</Subscript> thin film annealed at different temperatures

Pb(Zr_0.53Ti_0.47)O₃ (PZT) thin films were prepared on Pt/Ti/SiO₂/Si substrate by sol–gel method. The effect of annealing temperature on microstructure, ferroelectric and dielectric properties of PZT films was investigated. When the films were annealed at 550–850 °C, the single-phase PZT films were obtained. PZT films annealed at 650–750 °C had better dielectric and ferroelectric properties. The sandwich composites with epoxy resin/PZT film with substrate/epoxy resin were prepared. The annealing temperature of PZT films influenced their damping properties, and the epoxy-based composites embedded with PZT film annealed at 700 °C had the largest damping loss factor of 0.923.     

Optical and photoelectric properties of Cd<Subscript>1 - <Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>x</Subscript>As<Subscript>2</Subscript> single crystals

The optical absorption, photoconductivity, and short-circuit photocurrent spectra of structurally perfect Cd_{1 - x} Zn_xAs₂ (x = 0.03, 0.05, 0.06) single crystals are studied for the first time near the intrinsic edge in the range 80–300 K. The results demonstrate that the intrinsic edge in the solid solutions is due to indirect transitions involving the formation of excitons for both the E c and E c polarizations. The indirect gaps _g ⁱ of the solid solutions are determined. In the range 80–300 K, the data for x = 0–0.06 and both polarizations are well fitted by _g ⁱ (x) = _g ⁱ (0) + 0.0866x + 2.35x ². The introduction of 6 mol % ZnAs₂ into CdAs₂ increases its _g ⁱ by 14 meV.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 268–272.Original Russian Text Copyright © 2005 by Morozova, Marenkin, Mikhailov, Koshelev.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Characterization and optoelectronic properties of sol-gel-derived CuFeO2 thin films

In this study, CuFeO₂ thin films were deposited onto quartz substrates using a sol-gel and a two-step annealing process. The sol-gel-derived films were annealed at 500 °C for 1 h in air and then annealed at 600 to 800 °C for 2 h in N₂. X-ray diffraction patterns showed that the annealed sol-gel-derived films were CuO and CuFe₂O₄ phases in air annealing. When the films were annealed at 600 °C in N₂, an additional CuFeO₂ phase was detected. As the annealing temperature increased above 650 °C in N₂, a single CuFeO₂ phase was obtained. The binding energies of Cu-2p_3/2, Fe-2p_3/2, and O-1s were 932.5 ± 0.1 eV, 710.3 ± 0.2 eV and 530.0 ± 0.1 eV for CuFeO₂ thin films. The chemical composition of CuFeO₂ thin films was close to its stoichiometry, which was determined by X-ray photoelectron spectroscopy. Thermodynamic calculations can explain the formation of the CuFeO₂ phase in this study. The optical bandgap of the CuFeO₂ thin films was 3.05 eV, which is invariant with the annealing temperature in N₂. The p-type characteristics of CuFeO₂ thin films were confirmed by positive Hall coefficients and Seebeck coefficients. The electrical conductivities of CuFeO₂ thin films were 0.28 S cm^− 1 and 0.36 S cm^− 1 during annealing at 650 °C and 700 °C, respectively, in N₂. The corresponding carrier concentrations were 1.2 × 10¹⁸ cm^− 3 (650 °C) and 5.3 × 10¹⁸ cm^− 3 (700 °C). The activation energies for hole conduction were 140 meV (650 °C) and 110 meV (700 °C). These results demonstrate that sol-gel processing is a feasible preparation method for delafossite CuFeO₂ thin films.     

Fabrication and electrical properties of Ba0.64Sr0.36TiO3 thin films by sol-gel on platinum coated silicon

The Ba_0.64Sr_0.36TiO₃ thin films have been prepared by the sol-gel method on a platinum-coated silicon substrate. The structure and electrical properties of sol-gel derived Barium-strontium-titanate (Ba_0.64Sr_0.36TiO₃) thin films have been investigated. The as-fired thin films are found to be amorphous, and the films crystallize to a perovskite structure after a post deposition annealing at 700°C for 1 h in air. The dielectric constant and dissipation factor for Ba_0.64Sr_0.36TiO₃ thin film at a frequency of 200 Hz were 592 and 0.028, respectively. The temperature dependence of dielectric constant and dissipation factor exhibited a diffused ferroelectric to paraelectric phase transition at 40°C. The ferroelectric nature of this film at room temperature was confirmed by the existence of butterfly-shaped C-V curves caused by switching of the ferroelectric domains. The capacitance changed from 495 to 1108 pF with the applied voltage in the –5 to +5 V range at a frequency of 100 kHz. The pyroelectric coefficient at room temperature (25°C) is 1860 C/m²K, and the figure-of-merit of this film is 37.4 C/m³K. The high pyroelectric coefficients and the greater figures of merit of Ba_0.64Sr_0.36TiO₃ thin films make it possible to be used for thermal infra-red detection and imaging.