X-ray powder diffraction (XRD) along with differential thermal analysis (DTA) carried out on the as-quenched samples in the 3BaO-3TiO2-B2O3 system confirmed their amorphous and glassy nature, respectively. The dielectric constants in the 1 kHz-1 MHz frequency range were measured as a function of temperature (323-748 K). The dielectric constant and loss were found to be frequency independent in the 323-473 K temperature range. The dielectric behavior was consistent with the universal dielectric response (UDR). The temperature coefficient of dielectric constant was estimated using Havinga's formula and found to be 16 ppm.K-1. The electrical relaxation was rationalized using the electric modulus formalism. The dielectric constant and loss were 17 \pm 0.5 and 0.005 \pm 0.001, respectively at 323 K in the 1 kHz-1 MHz frequency range which may be of considerable interest to capacitor industry.
The two-step heat treatment method is used to measure the steady state crystal nucleation rate and induction time as a function of temperature in BaO.2SiO2 and 5BaO.8SiO2 glasses. For both glasses, the temperature for maximum nucleation rate and the temperature range for significant nucleation agree well with previous estimates from differential thermal analysis studies. The data are analyzed with a new iterative method to obtain the interfacial free energy and critical work of cluster formation as a function of temperature. For temperatures below the temperature at which steady-state nucleati…
Transparent SrO-0.5Li2O-4.5B2O3 (SLBO) and BaO-0.5Na2O-4.5B2O3 (BNBO) glasses were fabricated via the conventional melt-quenching technique. The amorphous and glassy characteristics of the as-quenched samples were respectively confirmed by X-ray powder diffraction (XRD) and Differential Thermal Analysis (DTA) studies. Optically clear SLBO and BNBO glass nano/microcrystal composites were obtained by heat-treating the as-quenched glasses slightly above their respective glass transition temperatures. These glass nano/microcrystal composites exhibited second harmonic signals in transmission mode w…
We show that the experimentally observed behavior of thermal conductivity of dielectric glasses over a wide temperature range can be explained by a combination of two scattering processes. The first one comes from the phonon scattering due to biaxial dipoles of wedge disclinations while the second one is the Rayleigh type scattering. The results obtained support the cluster picture suggested earlier for glassy materials.
Dielectric permittivity and Second Harmonic Generation (SHG) studies in the field-cooled mode show a linear dependence of dielectric stiffness (inverse dielectric permittivity) on dc bias in PMN-PT crystals and SHG intensity in KTaO$_{3}$:Li at small Li concentrations. We explain this unusual result in the framework of a theory of transverse, hydrodynamic-type, instability of local polarization.
Electrical conduction and relaxation phenomena in bismuth borate glasses in the composition 2Bi2O3-B2O3 (Bi4B2O9) were investigated. Dielectric studies carried out on these glasses revealed near constant loss (NCL) response in the 1 kHz to 1MHz frequency range at moderately high temperatures (300-450K) associated with relatively low loss (D=0.006) and high dielectric constant (εr'=37) at 1kHz,300K. The variation in AC conductivity with temperature at different frequencies showed a cross over from NCL response characterized by local ion vibration within the potential well to universal Joncher's…
The frequency and temperature dependence of the dielectric constant and the electrical conductivity of the transparent glasses in the composition Li2O-3B2O3 (LBO) were investigated in the 100 Hz- 10 MHz frequency range. The dielectric constant and the loss in the low frequency regime were electrode material dependent. Dielectric and electrical relaxations were respectively analyzed using the Cole-Cole and electric modulus formalisms. The dielectric relaxation mechanism was discussed in the framework of electrode and charge carrier (hopping of the ions) related polarization using generalized Co…
The glasses in the system (100-x)TeO2-xCaCu3Ti4O12, (x=0.25 to 3 mol %) were fabricated. The color varied from olive green to brown as the CaCu3Ti4O12 (CCTO) content increased in TeO2 matrix. The X-ray powder diffraction and differential scanning calorimetric analyses that were carried out on the as-quenched samples confirmed their amorphous and glassy nature respectively. The dielectric constant and loss in the 100 Hz-1MHz frequency range were monitored as a function of temperature (50-400oC). The dielectric constant and the loss (D) increased as the CCTO content increased in TeO2 at all the …
The frequency and temperature dependence of the dielectric constant and the electrical conductivity of the transparent glasses in the composition 0.5Cs2O-0.5Li2O-3B2O3 (CLBO) were investigated in the 100 Hz - 10 MHz frequency range. The dielectric constant for the as-quenched glass increased with increasing temperature, exhibiting anomalies in the vicinity of the glass transition and crystallization temperatures. The temperature coefficient of dielectric constant was estimated (35 \pm 2 ppm.K-1) using Havinga's formula. The dielectric loss at 313 K is 0.005 \pm 0.0005 at all the frequencies un…
The frequency and temperature dependence of the dielectric constant, electric modulus and electrical conductivity of the transparent glasses in the composition 0.5Li2O-0.5Na2O-2B2O3 (LNBO) were investigated in the 100 Hz - 10 MHz frequency range. The dielectric data have been analyzed using Cole-Cole equation with an addition of the conductivity term. The electrical conductivity was found to be obeying Jonscher's universal law. The dielectric constant and the loss for the as-quenched glasses increased with increasing temperature, exhibiting anomalies in the vicinity of the glass transition and…
The efficiency of glass ceramic sealants plays a crucial role in high temperature applications performance and durability, such as oxygen separation from air. In order to develop suitable sealants, operating at about 950C, several glass-ceramics with different compositional additives and ratios in BAS system have been prepared and investigated. The effects of additive oxides, CaO, CoO, B2O3, as network modifiers on the thermal and dielectric properties of BAS glass-ceramic for further oxygen transport membrane OTM applications were evaluated and discussed. The addition of additives has evident…
Ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. In this context, new phosphate glass-ceramics 2BaO-0.5Na2O 2.5[(1-x)Nb2O5 xWO3]-1P2O5 (x=0, 0.1, 0.2, 0.3 and 0.4) designated as B0, B1, B2, B3, B4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 °C for 10 hours. Subsequently, the obtained glass-ceramics were studied by Differential Scanning Calorimetry (DSC), X-ray powder diffraction (XRD), Raman, impedance spectros…
Transparent glasses in the system 0.5Li2O-0.5M2O-2B2O3 (M=Li, Na and K) were fabricated via the conventional melt quenching technique. Amorphous and glassy nature of the samples were confirmed via the X-ray powder diffraction and the differential scanning calorimetry, respectively. The frequency and temperature dependent characteristics of the dielectric relaxation and the electrical conductivity were investigated in the 100 Hz - 10 MHz frequency range. The imaginary part of the electric modulus spectra was modeled using an approximate solution of Kohrausch-Williams-Watts relation. The stretch…
We compute the dielectric response of glasses starting from a microscopic system-bath Hamiltonian of the Zwanzig-Caldeira-Leggett type and using an ansatz from kinetic theory for the memory function in the resulting Generalized Langevin Equation. The resulting framework requires the knowledge of the vibrational density of states (DOS) as input, that we take from numerical evaluation of a marginally-stable harmonic disordered lattice, featuring a strong boson peak (excess of soft modes over Debye $\simω_{p}^{2}$ law). The dielectric function calculated based on this ansatz is compared with expe…
It has been considered that polar nanoregions in relaxors form at Burns temperature Td approx 600 K. High-temperature dielectric investigations of Pb(Mg1/3Nb2/3)O3 (PMN) and 0.7PMN-0.3PbTiO3 reveal, however, that the dielectric dispersion around 600 K appears due to the surface-layer contributions. The intrinsic response, analyzed in terms of the universal scaling, imply much higher Td or formation of polar nanoregions in a broad temperature range, while high dielectric constants manifest that polar order exists already at the highest measured temperatures of 800 K. The obtained critical expon…
The dielectric anomalies of window-type glasses at low temperatures ($T<$ 1 K) are rather successfully explained by the two-level systems (2LS) tunneling model (TM). However, the magnetic effects discovered in the multisilicate glasses in recent times \cite{ref1}-\cite{ref3}, and also some older data from mixed (SiO$_2$)$_{1-x}$(K$_2$O)$_x$ and (SiO$_2$)$_{1-x}$(Na$_2$O)$_x$ glasses \cite{ref4}, indicate the need for a suitable generalization of the 2LS TM. We show that, not only for the magnetic effects \cite{ref3,ref5} but also for the mixed glasses in the absence of a field, the right exten…
Low frequency dielectric measurements on plexiglass (PMMA) show that cooling and heating the sample at constant rate give an hysteretic dependence on temperature of the dielectric constant $ε$. A temporary stop of cooling produces a downward relaxation of $ε$. Two main features are observed i) when cooling is resumed $ε$ goes back to the values obtained without the cooling stop (i.e. the low temperature state is independent of the cooling history) ii) upon reheating $ε$ keeps the memory of the aging history ({\it Memory}). The analogies and differences with similar experiments done in spin gla…
The spin glasses are disordered and frustrated magnetic systems. They show aging phenomena which are also a characteristic feature of structural glasses, polymers, dielectrics, colloids, etc. Under a strong enough magnetic field variation, spin glasses can be "rejuvenated", in the same way as glasses under a high enough stress. But spin glasses also display non-trivial "rejuvenation and memory" effects when they are submitted to temperature variations. Comparable phenomena have recently been identified in some polymers and gels, although less sharply pronounced. We propose to describe aging ph…
Amorphous solids or glasses are known to exhibit stretched-exponential decay over broad time intervals in several of their macroscopic observables: intermediate scattering function, dielectric relaxation modulus, time-elastic modulus etc. This behaviour is prominent especially near the glass transition. In this Letter we show, on the example of dielectric relaxation, that stretched-exponential relaxation is intimately related to the peculiar lattice dynamics of glasses. By reformulating the Lorentz model of dielectric matter in a more general form, we express the dielectric response as a funct…
Characterizing the frequency-dependent response of amorphous systems and glasses can provide important insights into their physics. Here, we study the response of an electron glass, where Coulomb interactions are important and have previously been shown to significantly modify the conductance and lead to memory effects and aging. We propose a model which allows us to take the interactions into account in a self-consistent way, and explore the frequency-dependent conduction at all frequencies. At low frequencies conduction occurs on the percolation backbone, and the model captures the variable-…
Phase-coexistence in the manganese-oxide compounds or manganites with colossal magneto-resistance (CMR) has been generally considered to be an inhomogeneous ground state. An alternative explanation of phase-coexistence as the manifestation of a disorder-broadened first order magnetic phase transition being interrupted by the glasslike arrest of kinetics is now gradually gaining ground. This kinetic arrest of a first order phase transitions, between two states with long-range magnetic order, has actually been observed in various other classes of magnetic materials in addition to the CMR mangani…
Quantum two-level systems (TLSs) intrinsic to glasses induce decoherence in many modern quantum devices, such as superconducting qubits. Although the low-temperature physics of these TLSs is usually well-explained by a phenomenological standard tunneling model of independent TLSs, the nature of these TLSs, as well as their behavior out of equilibrium and at high energies above 1 K, remain inconclusive. Here we measure the non-equilibrium dielectric loss of TLSs in amorphous silicon using a superconducting resonator, where energies of TLSs are varied in time using a swept electric field. Our re…
This paper presents accurate data for the physical aging of organic glasses just below the glass transition probed by monitoring the following quantities after temperature up and down jumps: the shear-mechanical resonance frequency (around 360 kHz), the dielectric loss at 1 Hz, the real part of the dielectric constant at 10 kHz, and the loss-peak frequency of the dielectric beta process (around 10 kHz). The setup used allows for keeping temperature constant within 100 micro Kelvin and for thermal equilibration within a few seconds after a temperature jump. The data conform to a new simplified …
Samarium doped Na$_2$O-ZnO-TeO$_2$ (NZT) glasses were prepared by the melt quenching method. The glass-forming ability and glass stability of prepared glass was estimated by Hruby parameter using Differential Thermal Analysis (DTA) and Thermo-gravimetric Analysis (TGA). The study of FTIR spectra and X-ray diffraction described the ionic nature and the amorphous pattern of glass respectively. The absorption peaks were observed for the transitions 6H5/2-4P3/2 at 402 nm,6H5/2-4M19/2 at 418 nm, 6H5/2-4I15/2 at 462 nm and 6H5/2-4I11/2 at 478 nm in the absorption spectra. The optical band gap energy…
We have investigated the magnetic, dielectric and magnetodielectric (MDE) behavior of a geometrically frustrated spin-chain system, Ca3Co1.4Rh0.6O6, in the single crystalline form for different orientations. The results bring out that the magnetic behavior of this compound is by itself interesting in the sense that this compound exhibits an anisotropic glassy-like magnetic behavior with a huge frequency dependence of ac susceptibility peak for an orientation along the spin-chain in the range 30-60 K; this behavior is robust to applications of large external magnetic fields (H) unlike in canoni…
A new kind of memory effect on low frequency dielectric measurements on plexiglass (PMMA) is described. These measurements show that cooling and heating the sample at constant rate give an hysteretic dependence on temperature of the dielectric constant $ε$. A temporary stop of cooling produces a downward relaxation of $ε$. Two main features are observed i) when cooling is resumed $ε$ goes back to the values obtained without the cooling stop (i.e. the low temperature state is independent of the cooling history) ii) upon reheating $ε$ keeps the memory of all the cooling stops({\it Advanced memor…
Neodymium doped Na2O-ZnO-TeO2 (NZT) glasses were prepared by the conventional melt quenching technique. DTA and TG were used to confirmation of glass preparation through the glass transition temperature at 447°C for the glass system. The analysis of FTIR spectra and X-ray diffraction described the nature of the samples were ionic and amorphous respectively. The optical bandgap energy was estimated using absorption spectra and found to be decreased from 2.63eV to 1.32 eV due to the increase of doping concentration. The intensity of the emission spectra was enhanced for the higher concentration …
Topological defects are typically quantified relative to ordered backgrounds. The importance of these defects to the understanding of physical phenomena including diverse equilibrium melting transitions from low temperature ordered to higher temperatures disordered systems (and vice versa) can hardly be overstated. Amorphous materials such as glasses seem to constitute a fundamental challenge to this paradigm. A long held dogma is that transitions into and out of an amorphous glassy state are distinctly different from typical equilibrium phase transitions and must call for radically different …
We applied the recently developed Generalized Langevin Equation (GLE) approach for dielectric response of liquids and glasses to link the vibrational density of states (VDOS) to the dielectric response of a model orientational glass (OG). The dielectric functions calculated based on the GLE, with VDOS obtained in experiments and simulations as inputs, are compared with experimental data for the paradigmatic case of 2-adamantanone at various temperatures. The memory function is related to the integral of the VDOS times a spectral coupling function $γ(ω_p)$, which tells the degree of dynamical c…
Neutron diffraction studies using powder samples have been used to understand the complex sequence of low temperature phase transitions of NaNbO3 in the temperature range from 12 K-350 K. Detailed Rietveld analysis of the diffraction data reveal that the antiferroelectric to ferroelectric phase transition occurs on cooling around 73 K while the reverse ferroelectric to antiferroelectric transition occurs on heating at 245 K. However, the former transformation is not complete till down to 12 K and there is unambiguous evidence for the presence of the ferroelectric R3c phase coexisting with an a…
Many frequency-response analyses of experimental data for homogeneous glasses and single-crystals involving mobile ions of a single type indicate that estimates of the stretched-exponential beta1 shape parameter of the Kohlrausch K1 fitting model are close to 1/3 and are virtually independent of both temperature and ionic concentration. This model, which usually yields better fits than others, is indirectly associated with temporal-domain stretched-exponential response having the same beta1 parameter value. Here it is shown that for the above conditions several different analyses yield the imp…
