Temperature Dependence Of Resonance Frequency Research Articles

The order–disorder transition in Bi 2O 3–Nb 2O 5 fluorite-like dielectrics

An analysis of the microwave dielectric properties showed that the cubic fluorite solid solutions (1 − x)Bi 2O 3· xNb 2O 5 (0.23 ≤ x ≤ 0.26), the so-called δ-BN SS Type II, exhibit a high permittivity of 100, but also high dielectric losses ( Q × f = 300 GHz) and a high temperature dependence of resonant frequency ( τ f = −200 ppm/K). Investigations using X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that the cubic incommensurate phase undergoes an order–disorder phase transition into a commensurate tetragonal phase at temperatures below 900 °C (for x = 0.25). The higher degree of ordering in the tetragonal phase reduces the dielectric losses ( Q × f = 1000 GHz) and changes the sign of the temperature coefficient of resonant frequency ( τ f = 100 × 10 −6/K).

Development of low cost, high performance Ba(Zn1/3Nb2/3O3) based materials for microwave resonator applications

Solid solutions of the (x)Ba(Zn1/3Nb2/3)O3 – (1-x)Ba(Co1/3Nb2/3)O3 system were produced by the mixed oxide route. Sintering temperatures of 1300–1500 °C with cooling rates of 3–180 °C/h were used. Sintered densities of ⩽95% were achieved. A second phase deficient in Co and Zn was detected. Slow cooling after sintering, down to 900 °C, induced B-site ordering which increased the dielectric Q values. Compositions near to 0.6[Ba(Zn1/3Nb2/3)O3] – 0.4[Ba(Co1/3Nb2/3)O3] exhibited zero temperature dependence of resonant frequency (τf ∼0). The presence of the second phase (Zn/Co deficient) improved the dielectric properties. Ceramics of optimum composition, having x∼0.6, have excellent electrical properties, (Q value ∼43,000 at 2 GHz, relative permittivity εr ∼35.5 and τf tunable through zero). The material will offer a new design option for filter engineers in the development of 3G and other similar telecommunication systems.

Studies of molecular dynamics of thiazides by35Cl NQR spectroscopy and DFT calculation

Molecular dynamics of three derivatives of 1,2,4-benzothiadiazine-1,1-dioxide, hydrochlorothiazide (HCTZ), althiazide (ATZ) and chlorothiazide (CTZ), was studied by35Cl nuclear quadrupole resonance (NQR) spectroscopy. The temperature dependence of the resonance frequency was analyzed within the 6 known standard models. The activation energies estimated from the temperature dependence of the35Cl NQR frequency assuming the Bayer model were 1.07, 2.35 and 2.76 kJ/mol for HCTZ, ATZ and CTZ respectively, which confirms that HCTZ is less rigid than CTZ and ATZ is much more rigid than HCTZ, and suggests that the mechanism of relaxation is based on small amplitude librations. The characteristic temperatures estimated from the Bayer model, with that for CTZ (332.5 K) being much higher than for HCTZ (132.1 K), mean that the intermolecular interactions in CTZ are much stronger than in HCTZ, as suggested by the melting point of CTZ being higher than that for HCTZ. For ATZ the characteristic temperature (288 K) takes an intermediate value, which suggests that the intermolecular interactions in this compound are stronger than in HCTZ and weaker than in CTZ. A significant narrowing of the resonance35Cl NQR line observed for all these compounds at room temperature, relative to that at the liquid nitrogen temperature, suggests an averaging of dipolar interactions as a result of fast rotation of nonquadrupole nuclei in the vicinity of the quadrupole nuclei, when 2πνQτc ≫ 1 (a rotation of the −NH2 group in the direct neighborhood of the chlorine nuclei) or a change in the gradient orientation with its value preserved (which is equivalent to rotation of the quadrupole nucleus Cl). The influence of the rotations of the −NH2 and −CH2SCH2CH=CH2 groups (ATZ) or −CHCl2 group (TCTZ) on the35Cl NQR frequency was modelled by the B3LYP/6-31G* method. The frequencies of the libration vibrations calculated from the temperature dependence of the NQR resonance frequency were compared with experimental ones and those implied by the density functional theory, infrared and Raman spectra. For HCTZ the anomalies in the temperature dependence of the35Cl NQR frequency, the lack of hysteresis and small but notable changes in the slope and the jump in the frequency observed at 253 K which does not exceed 0.05 MHz suggest a second-order phase transition at 253 K.

Dynamical Properties of the FR(LT)-FR(HT) Phase Transition in Zr-Rich Lead Zirconate Titanate Ceramics

The dielectric, elastic and piezoelectric properties of the F R(LT)-F R(HT) phase transition were investigated on Nb-doped lead zirconate titanate (PZT) Pb(Zr1-xTix)O3 ceramics (x=0.05 and 0.25). Dielectric anomaly and thermal hysteresis are observed through the F R(LT)-F R(HT) phase transition in PZT(Nb)95/5, but no anomaly appears in PZT(Nb)75/25. Two compositions show pronounced dielectric dispersions in the rhombohedral ferroelectric phases. The temperature dependences of resonance frequency (f r), elastic constant (s11 E) and Poisson's ratio(σ) show remarkable anomalies around the F R(LT)-F R(HT) phase transition in both compositions. However, the temperature range of the anomaly of PZT(Nb)75/25 is much broader than that of PZT(Nb)95/5. The electromechanical coupling factor (K p) decreases abruptly in PZT(Nb)95/5, while, in contrast, it increases gradually in PZT(Nb)75/25. These results are discussed on the basis of the coupling of M-type and R-type oxygen octahedral tilts to polarization and strain.

Temperature Dependence of Resonance Frequency of Shape-Memory Alloy Vibrated Photothermally

The temperature dependence of the resonance frequency for a cantilever of a shape-memory alloy vibrated photothermally is described. The temperature coefficient of the resonance frequency of the alloy with memory for shape recovery was positive (2.0×10-2/° C) at a temperature near the martensitic transformation, in contrast with it being negative (-2.2×10-3/° C) for the alloy without memory. The technique of using one laser for both excitation and detection was adopted for determining the resonance frequency of the photothermal vibration.

TICaBaCuO high Tc superconducting microstrip ring resonators designed for 12 GHz

Microwave properties of sputtered TICaBaCuO thin films were investigated by designing, fabricating and testing microstrip ring resonators. Ring resonators designed for 12 GHz fundamental resonance frequency, were fabricated and tested. From the unloaded Q values for the resonators, the surface resistance was calculated by separating the conductor losses from the total losses. The penetration depth was obtained from the temperature dependence of resonance frequency, assuming that the shift in resonance frequency is mainly due to the temperature dependence of penetration depth. The effective surface resistance at 12 GHz and 77 K was determined to be between 1.5 and 2.75 mΩ, almost an order lower than Cu at the same temperature and frequency. The effective penetration depth at 0 °K is approximately 7000 Å.

Vibration analysis of length extensional mode quartz crystal resonator with plural vibration bars

AbstractA length extensional mode quartz crystal resonator of small size and good antishock performance and which functions at relatively low frequencies of 200 kHz to 1.536 MHz has been used in pagers and IC cards. An on/off repetition in quartz resonators of this type is common and therefore the start‐up transient performance becomes important.This paper describes a length extensional mode quartz crystal resonator with plural vibration bars which has a short start‐up time. The objective of this paper is to clarify both theoretically and experimentally motional inductance L1, frequency characteristics and temperature dependence of resonance frequency, and also electric properties of the resonator.Motional inductance L1 is derived first. Especially, L1 is found theoretically to be inversely proportional to the number of bars. Next, a vibration analysis of bars and supporters is made by taking into account the lateral motions based on an energy method and then a frequency equation is derived. The frequency characteristics, temperature dependence of resonance frequency, and electric properties are analyzed and compared with experimental results. The calculated results are found to be in agreement with the experimental ones. Finally, it is shown that a length extensional mode quartz resonator exhibits a short start‐up time, since L1 and R1 are compared to the single‐bar case. Such resonators are believed to be manufactured in a small form and also exhibit a good anti‐shock performance since vibrational and supporting portions can be made as one solid body by an etching method.

Piezoelectric resonance detection of single grain rochelle salt crystal

Abstract Piezoelectric resonance signal is observed from a crystalline minute single grain (size∼0.4 mm × 0.4 mm × 0.6 mm, mass ∼100 μg) Rochelle salt by using an inductive pulse detection method. A kink in the temperature dependent resonance frequency at the high Curie temperature T ch = 24°C is clearly seen from our measurements with open circuited condition. The kink, which was noted as a morphic effect, is smeared by the applied do electric field. The electric field also induces changes in the resonance frequency in such ways that δf, × k,E + k2E2 and δf, ×E for the high and low temperature nonferroelectric phases, respectively.

New-type calorimetric gas sensor using temperature characteristics of piezoelectric quartz crystal fitted with noble metal catalyst film

A new type of piezoelectric crystal sensor coated with a sputtered noble metal (Pt, Pd, Ir, or Pt-Ir) film is proposed for the detection of inflammable gases, such as H 2, CO and isobutane diluted with air, in the temperature range 100–400 °C. Its sensing principle utilizes an increase in resonance frequency of the quartz crystal with the increase in temperature due to the oxidation of an inflammable gas on the coated catalyst film. Experiments show that the sensitivity increases linearly with H 2 concentration up to 0.4 vol.%, with a 90% response time of about 20 s to 0.3 vol.% H 2 at 200 °C. The sensitivity is dependent on the operation temperature due to the temperature-dependent resonance frequency of the crystal. Among the various coating films tested, sputtered Pt-Ir film gives the best sensor, with high sensitivity to inflammable gases and high resistance to interference by coexisting water vapour.

Temperature dependence of resonant frequency in all-fibre optically addressed silicon microresonator sensors

A compact sensor head for pressure and temperature measurements has been developed and demonstrated. The temperature dependence of resonant frequency in such a sensor system has been measured and analysed. It has been determined from the observed results that the additional thermal expansion of the substrate used to fix the silicon bridge results in a decrease of the overall temperature sensitivity of resonant frequency. The overall temperature coefficient of resonant frequency changes from a positive to a negative value and gradually reduces as temperature increases.

Study on the Light Scattering Mechanism at Precipitates on Dislocation Lines in an Indium Doped GaAs Crystal

The light intensities scattered from the precipitates on dislocations in an In-doped GaAs crystal were measured as a function of the temperature with three different frequencies of lasers. The scattered intensity showed a few peaks from 30 K to 260 K depending upon the wave length of the incident beams. The temperature dependence of resonance frequencies was obtained by Ogawa's resonance scattering model (R.S.M.) and compared with the experimental result.

Silicon resonator sensors: interrogation techniques and characteristics

Interferometric and noninterferometric optical-fibre sensing systems for resonator vibrations are described. The quality factor variation with pressure, the temperature dependence of resonant frequency and the acceleration sensitivity are given for a double-ended tuning-fork based acceleratometer.

Temperature dependence of resonant frequency in optically excited diaphragms

Silicon diaphragms of 4 μm thickness, fabricated by anisotropic etching techniques, are coated with a thin layer of aluminium. An intensity-modulated laser beam focused on the diaphragm generates transverse vibrations which are detected interferometrically. The measured deflections, resonant frequencies and temperature dependence of resonant frequencies are reported.

High-Q Dielectric Resonator Sintered at Low Firing Temperature

The microwave properties of dielectric resonators were investigated. The dielectric ceramics with Ba(Mg, Co)1/3 Nb2/3O3-Ba(Co1/3Ta2/3)O3 system were found to be fired at a low temperature below 1400°C and to have high-εr and high-Q value. Dielectric properties at microwave frequency were measuered. Dielectric properties of the ceramic resonator were dielectric constant of 31, the Q-value of 10000 at 10 GHz. The temperature dependence of resonant frequency was 0.25 ppm/°C from -40°C to 100°C.

A low-cost digital temperature sensor system

Suitably cut quartz crystals exhibit a temperature dependent resonance frequency. This can be used for a fully digital temperature measurement system. Various properties of several mass producted sensor quartzes have been measured over the temperature range −25°C to 75°C, including temperature coefficient, non-linearity, reproducibility and influence of lead temperature. A single conventional circuit for analog quartz clocks is used as an oscillator, divider and as a noise-immune two-wire digital transmission system. The supply current is modulated with a factor of > 100 in temperature-dependent time intervals of approximately 1 s. This technique is especially suitable for microprocessors with an internal counter. With single poiny calibration, system accuracies are in the range 10 mK– 100 mK.

14N Nuclear Quadrupole Resonance in Simple Compounds Containing the Amino Group

Abstract14N nuclear quadrupole resonance was observed in acetamide, CH3CONH2, and chloroacetamide, CH2ClCONH2, by pulse technique. The resonance frequencies in both compounds increase with raising from 80 K to 340 K. In acetamide the activation energy was calculated to be 17.6 kJ · mol−1 in the temperature range from 260 K to 320 K and 48.1 kJ · mol−1 above 320 K. The former is thought to be attributed to the reorientation of the amino group and the latter, to the torsional motion of molecule. In the case of chloroacetamide the echo signal is too weak to obtain the correct T1 value, but the relaxation mechanism seems to be similar to that of acetamide. The positive temperature dependence of resonance frequencies is due to the hydrogen bond.

NMR Study of 59Co in Gd1-xYx (Fe.7Co.3)2 and Gd1-xYx (Fe.5Co.5)2

Nuclear magnetic resonance of 59 Co nuclei in Gd 1- x Y x (Fe .7 Co .3 ) 2 and Gd 1- x Y x (Fe .5 Co .5 ) 2 has been observed at 77 K as a function of Y concentration. The contribution of 4f electrons of Gd atoms to the hyperfine fields is estimated as at most 10 kOe in these two systems. This value is interpreted as the sum of the change in three kinds of contributions caused by Y substitution; the core polarization in the central Co atom, the conduction electron polarization arising from nearest neighbor Fe and Co atoms and the transferred hyperfine field from neighboring Gd atoms. The temperature dependence of resonance frequencies in Gd(Fe .7 Co .3 ) 2 and Gd(Fe .5 Co .5 ) 2 has also been measured.

Single Crystal Growth and Pyroelectric, Dielectric, Piezoelectric, Elastic, and Thermoelastic Properties of Orthorhombic Li2SiO3, Li2GeO3, and Na2GeO3

AbstractSingle crystals of optical quality of isotypic Li2SiO3, Li2GeO3, and Na2GeO3, space group Ccm21, with diameters of ca 16 mm and lengths of ca 20 mm (Li2SiO3) and ca 60 mm (Li2GeO3 and Na2GeO3) have been grown from the melt using the Czochralski technique. On Li2SiO3, Li2GeO3, and Na2GeO3 pyroelectric coefficients and complete dielectric, piezoelectric, elastic, and thermoelastic tensor properties have been determined; the latter from the temperature dependence of resonance frequencies. All crystals investigated exhibited only a small amount of 180° twins. They all possess large pyroelectric coefficients about‐five times that of tourmaline. The longitudinal piezoelectric constant d333 is about five times larger than d111 of alpha quartz. Qualitative measurements on Na2SiO3 revealed similar values of pyroelectric and piezoelectric effects. The technical application of these crystals encounters some difficulties: Li2SiO3 is excellently cleavable parallel (010). This face contains the polar direction [001]. Na2GeO3 suffers from chemical decomposition in humid atmosphere and is well cleavable too. Both happens to a much less extent in Li2GeO3. Na2SiO3 proved to be hardly suitable for any application of its polar properties due to its bad chemical stability against humid air and its excellent cleavage.

Nuclear quadrupole resonance of nitrogen-14 in some primary aliphatic amines

The nuclear quadrupole resonance of 14N in ethylamine, n-propylamine, isopropylamine, n-butylamine, and tert-butylamine were observed at liquid nitrogen temperature. For ethylamine, the temperature dependence of resonance frequencies was measured, and a phase transition was found at 184°K. The observed frequencies, ν I and ν II, yield almost the same quadrupole coupling constant and asymmetry parameter regardless of the kind of alkyl groups. The ionic character of NH and NC bonds was estimated as 0.42 and 0.27, respectively.

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