Dielectric Properties Of SrTiO3 Research Articles

Effect of the second phase on the microwave dielectric properties of strontium titanate

In this study, the effects of the second phase, either in the form of particulate or of lamella, on the microwave dielectric properties are investigated. Strontium titanate (SrTiO3) is considered to be a model system for this examination. Although SrTiO3 is an intermediate compound between SrO and TiO2, the solubilities of SrO and TiO2 in SrTiO3 are extremely low. Excess SrO and excess TiO2 lead to the formation of second phases as Sr3Ti2O7 and TiO2, respectively, within SrTiO3. TiO2 exists as particulates, and its presence marginally affects the microwave dielectric properties of SrTiO3. The Sr3Ti2O7 lamella is located on the long axis of the elongated SrTiO3 grain. With the formation of the Sr3Ti2O7 lamella, the permittivity decreases, and the product of quality factor and resonant frequency increases.

Giant permittivity and low dielectric loss of SrTiO3 ceramics sintered in nitrogen atmosphere

Abstract The dielectric properties of SrTiO 3 ceramics sintered in nitrogen (N 2 ) exhibit a weak temperature- and frequency-dependent giant permittivity (>10 4 ) as well as a very low dielectric loss (mostly

Effect of optical pump on the dielectric properties of SrTiO3 in terahertz range

Tuning the dielectric permittivity spectra of strontium titanate (SrTiO3) single crystals in an external optical field is investigated at room temperature by means of terahertz time-domain spectroscopy. The application of the optical field leads to an appreciable tuning of the permittivity, reaching up to 2.8%, with the dielectric loss changing about 3%. The observed behavior is interpreted in terms of soft-mode hardening due to the anharmonic character of its potential. We also find that the change of the refractive index responds linearly to the applied light power. These findings are attributed to a linear electro-optical effect of the internal space charge field of the crystal.

Effect of Pr substitution on structural and dielectric properties of SrTiO3

Pr-doped SrTiO3 ceramics were fabricated by the conventional solid-state reaction method. Pr-doping greatly decreased the lattice parameters and the average grain size of SrTiO3 ceramics sample. Two thermally activated dielectric relaxations were found for the low- and high-temperature relaxations, respectively. By means of a detailed analysis, the low-temperature relaxation was ascribed to the electric hopping between Pr3+ and Pr4+ induced by the Pr-doping, and the origin of the high-temperature relaxation was changed from oxygen vacancies to the polar nanoregions with the increase of Pr content.

Effect of Sample Size on Measurement Reliability of Microwave Dielectric Properties of Low-Loss Materials by a Resonant Cavity Method

The microwave dielectric properties of SrTiO3 and CaNdAlO4 single crystals were measured by the resonant cavity method, and the effect of sample size on measurement reliability was investigated. High measurement accuracy could always be achieved for SrTiO3, while the measurement was completely unreliable for CaNdAlO4 with small sizes. The difference was attributed to the much higher dielectric constant and electric energy filling factor of SrTiO3. It is indicated that the sample with much smaller size than usual might also be used for the resonant cavity method, as long as the electric energy filling factor of the sample was high enough.

Effect of Milling Time on Microstructure, Crystallite Size and Dielectric Properties of Srtio<sub>3 </sub>Ceramic Synthesized via Mechanical Alloying Method

SrTiO3 sample has been successfully prepared by mechanical alloying (MA) method. The effect of milling time on microstructure, crystallite size and dielectric properties of SrTiO3 were studied. The results revealed that the mean crystallite size of milled powders decreased from 84.56 to 12.87 nm with increasing milling time. However, the average lattice strain of milled powders increased from 0.2 to 0.93% with increasing milling time. A single phase SrTiO3 could not be formed with milling alone and required annealing process. A transformation of anatase-TiO2 to rutile-TiO2 was observed at 16 h of milling. After the milled powders were subjected to sintering process at 1200°C, formation of single-phase SrTiO3-type cubic (Pm-3m) perovskite structure was observed. The peak intensities of the sintered SrTiO3 samples decreased as the milling time was increased. For microstructural observations, the average grain size of the sintered SrTiO3 sample milled for 8 h showed the largest. For dielectric measurements, the dielectric constant of the sintered SrTiO3 sample milled for 8 h showed the highest among others. This could be due to the largest grain size obtained for sintered SrTiO3 sample milled for 8 h. The decrease in the grain size with increasing milling time resulted to the decrease in dielectric constant.

Microstructural studies and electrical properties of Mg-doped SrTiO 3 thin films

The structure–property relations of Mg-doped SrTiO 3 (ST) sol–gel thin films deposited on Pt/TiO 2/SiO 2/Si substrates have been investigated in order to determine the effect that Mg dopants have on the dielectric properties of SrTiO 3. It has been predicted that Mg-doped SrTiO 3 should exhibit a dielectric anomaly similar to that observed recently in Bi doped SrTiO 3 but, to date, no polar state has been reported. It has been suggested that this may relate to the low solubility of Mg on the A-site in bulk ceramics (<0.05 at.%). However, for Sr 1− x Mg x TiO 3 (SMT) ( x ⩽ 0.30) films annealed at 750 °C, all Mg ions were accommodated in the perovskite lattice and for SMT films annealed at 900 °C, the solubility limit of Mg was x = 0.10, above which a Mg-rich ilmenite second phase was observed. Irrespective of the higher solid solubility limit of Mg in the ST lattice for sol–gel ST films compared to equivalent ceramics, no ferroelectric or relaxor phase transition was observed, refuting previous predictions for this dopant.

Dielectric properties of SrTiO 3/POE flexible composites for microwave applications

Composites fabricated with SrTiO 3 ceramic filler dispersed inside a thermoplastic polyolefin elastomer (POE) polymer matrix, with excellent dielectric properties and good flexibility, have been studied in this paper. The relative permittivity of SrTiO 3/POE composites blended with different volume fraction of ceramic filler was investigated as a function of temperature and frequency. The results indicated that with the increase of ceramic filler, both the relative permittivity and the dissipation factor of composites increased. Good frequency stability within a wide range was observed in all the samples. The theoretical dielectric constant obtained from the effective medium theory of Bruggeman's model is in good agreement with the experimental data. For the composites containing 40 vol.% SrTiO 3, the dielectric constant and the loss tangent were 11.0 and 0.01 at 900 MHz, respectively, while the mechanical test results showed good flexibility on the final quality of the composites with the elongation of 90%. This indicates that the ST/POE composites have the promising characteristics for potential applications in the flexible dielectric waveguide and related flexible microwave devices.

Paraelectric ceramics/metal dual composites SrTiO3∕Pt system with giant relative permittivity

Dielectric properties of SrTiO3–Pt (platinum) composites prepared using conventional ceramic method were investigated. Dense complex ceramics were obtained without chemical reaction between SrTiO3 and Pt during sintering processes. The relative permittivity (εr) of SrTiO3 was increased by the addition of Pt particles nearly up to the percolation threshold of 27.8vol% as predicted using normalized percolation theory. The maximum εr of 2150 at 1MHz was obtained for the composite including 27vol% Pt due to the increased electric field around Pt particles. Using finite difference time domain method, the increase of electric field in the direction of applied electric field was confirmed visually in the vicinity of the embedded metal particles.

Characterization and dielectric properties of (SrTiO 3/BaTiO 3) n multilayer thin films deposited on Pt/Ti/SiO 2/Si substrates by double rf magnetron sputtering

The dielectric properties of SrTiO 3/BaTiO 3 multilayer thin films ((ST/BT) n ) prepared by double target rf magnetron sputtering have been characterized as a function of thickness, frequency and applied voltage. The XRD pattern shows the formation of the (ST/BT) 4 multilayers with designated modulation. The lattice strain increases from 0.30 to 1.2% when the layers number ( n) increases from 1 to 4. The dielectric constant increases with increasing layer number. The remanent polarization ( P r) and coercive field ( E c) are 3 and 7 μC/cm 2, and 20 and 60 kV/cm, respectively, for the (ST/BT) 2 and (ST/BT) 4 multilayers. The result shows that the (ST/BT) n multilayers exhibit ferroelectricity and have an increased E c, and decreased P r, as compared with the bulk material.

Effects of A-site ion size mismatch on dielectric properties of SrTiO3

In order to investigate the effects of A-site ionic size mismatch on the dielectric properties of SrTiO3, simultaneous substitution of Ca2+ and Ba2+ for Sr2+ was carried out while keeping the lattice parameter at a constant value. For samples with low substitution value, a quantum ferroelectric behavior was observed. As for those with high substitution value, a diffused phase transition was observed, indicating the existence of a relaxor-like substitution range.

Dielectric properties of SrTiO 3 thin films grown on various perovskite electrodes by pulsed laser deposition

The dielectric properties of SrTiO 3 (STO) thin films deposited on LaAlO 3 (LAO) substrates with various perovskite conducting layer including YBa 2Cu 3O 7 (YBCO), SmBa 2Cu 3O 7 (SmBCO), GdBa 2Cu 3O 7 (GBCO) and SrRuO 3 (SRO) as bottom electrode in a parallel-plate capacitor configuration were evaluated. The lattice mismatch between STO and different electrode materials varies markedly, but the dielectric constants of the STO films were not much different for different bottom electrodes. However, lower dielectric loss was observed in STO films on SRO electrodes. Under the optimum deposition conditions the tunability was large and the loss tangent was in the range of 0.001–0.01 at 1 kHz and zero bias field.

Dielectric properties of SrTiO3 and BST thin films fabricated using ECR-PEMOCVD

The SrTiO3 Thin films were deposited on Pt/SiO2/Si by ECR-PEMOCVD and their dielectric properties were investigated as a function of composition. The chemical bonding states of elements consisting these films were investigated using X-ray photoelectron spectroscopy (XPS) and Discrete Variational (DV)Xα simulation. The asymmetry of composition dependence on dielectric properties was explained by the XPS data. Further, effectiveness of NH3 carrier gas over Ar to deposit SrTiO3 is discussed in detail. Based on these data, the thickness dependence of dielectric constant of BST films was explained.

Sr/Ti ratio dependence of the dielectric properties of SrTiO3 thin films prepared by sol-gel method

Sr/Ti ratio dependence of the dielectric properties of SrTiO3 thin films prepared by sol-gel method

Atmosphere Control of Interface Migration and Its Effect on Dielectric Property of CuO‐Infiltrated Strontium Titanate

The control of interface migration and its effect on dielectric properties of SrTiO3 based materials have been investigated. SrTiO3 specimens with or without Nb2O5 doping were prepared, and the atmospheres of sintering and heat treatment were varied during the processing. It has been demonstrated that the change in defect structure at the interface of Nb‐doped SrTiO3 grains by atmosphere change was the cause of interface migration observed during CuO infiltration or heat treatment. The interface migration caused by sintering in a reducing atmosphere and infiltration in air could be suppressed by preoxidizing grain interfaces before the CuO infiltration in air. The suppression of migration increased the effective dielectric constant of the material.

Properties of Reactively Sputter Deposited SrTiO3 Films for IR Detector Readout Electronics

ABSTRACTThe effects of film thickness, oxygen partial pressure, electrode type, substrate temperature, and position on the room temperature and 77 K dielectric properties of SrTiO3 (ST) films were studied. The film composition and properties vary with radial position and oxygen partial pressure. A maximum in dielectric constant occurs near the same position where stoichiometric films are obtained. The room temperature and 77K dielectric constants increase with increasing thickness, while the capacitance density decreases. Capacitance densities as high as 4 fF/μm2 were observed for films deposited at low temperature and subsequently crystallized. Elevated temperature deposition, however, results in better properties than room temperature deposition followed by annealing. Dielectric constants as high as 200 with capacitance densities up to 9 fF/μ2 were observed. For optimized deposition conditions, no dielectric break-down of the capacitors was observed at 20V after 111 days of testing. The properties of capacitors with n+Si bottom electrodes were not as good as those with Ti/Pt electrodes, however, integration with Si integrated circuit processing is expected to be much simpler.