Ionic Packing Density Research Articles

Synthesis, characterization and optical studies of mixed alkali phosphate glasses containing MnO2

In this paper, new phosphate glasses with the general formula 40P2O5–10MnO2–(50-x)Li2O–xK2O, x= 5, 15, 25, 35, and 45 mol % were prepared using a conventional melt quenching technique. The mixed alkali effect (MAE) was explored in the physical and optical properties of the present glassy system. The amorphous nature of the samples was corroborated by X-ray diffraction analysis. The density of the glassy samples showed a nonlinear variation upon gradual replacement of Li2O by K2O, which is due to the MAE. From density, some physical parameters such as molar volume, lithium, potassium and manganese ion concentrations, ionic packing ratio and oxygen packing density were calculated for all samples. Nonlinear behavior of the optical parameters with K2O content supported the existence of the MAE in the optical properties of the system.

A Review on Physical and Optical Properties of Zinc Tellurite Glasses Co-doped with different rare earth ions

In this work we review the effect of physical and optical properties with different ion zinc contents of tellurite base glass. The physical properties of the glasses were evaluated and the change in density, molar volume and ionic packing density in these glasses indicates the effect of ZnO different content show on the glasses structure. The study of optical properties such as the optical band gap and refractive index of zinc tellurite glass were studied. Zinc Tellurite glasses doped with Er3+ ions were synthesized by varies researcher. The glasses were characterized by X- ray diffraction, optical absorption and photoluminescence spectra. The glassy nature of zinc Tellurite host glass has been confirmed through XRD measurements. The glasses doped or co-doped with rare-earth ions have generated much interest due to the possibility of several promising applications such as optical data storage, visible laser, fibre amplifier, optical communication and sensor devices

Physical, Structural, and Raman Spectroscopic Traits of Neodymium-Doped Lead Oxyfluoride Zinc Phosphate Glass

Nd3+ with composition of (60 - x) P2O5 - 10ZnO - 30PbF2 - (x) Nd2O3 where (0.0 ≤ x ≤ 2.0 mol %) was prepared using a melt-quenching approach to the development of transparent glasses. These glasses have been confirmed to be an amorphous structure through XRD analysis. The glass density, molar volume and ionic packing density were obtained in the range of 3.978-4.157 g cm−3, 41.949 - 41.073 cm3 mol−1 and 0.614-0.624, respectively. Using Fourier Transform Infrared (FTIR) and Raman Spectroscopy, the chemical functional groups and biomolecules of samples were characterised. The FTIR spectra revealed six main bands assigned to P-O, P-O-P, P=O, (PO3)2- and hydroxyl groups (O-H), while Raman shift detected five symmetric and asymmetric bands attributed to P-O-P bonds in Q1 units, (PO4)3- bonds in Q0 units, (PO3)2- bonds in Q1 units, (PO2)− bonds in Q2 units and P=O bonds in Q3 units. It is believed that the proposed oxyfluoride glasses may be useful and suitable applicant to lasing materials and sensors sensitivity.

Effect of ZrO2 addition on electrical and mechanical properties of B2O3–PbO–Li2O3 glasses

In this work, the electrical and mechanical properties of 40B2O3+40PbO+ 20Li2O3+xZrO2 (where x = 0.0, 0.25, 0.5, and 1.5 wt%) were experimentally investigated. The electrical and dielectric data were measured in the temperature range of 20–300 °C. Based on Makishima–Mackenzie's model, a total of dissociation energy (Gt) and the ionic packing density (Vt) for the investigated specimens were calculated. Then, the mechanical features, including Poisson's ratio and elastic moduli, were calculated. It was found that Vt decreased in the range of 0.3708–0.3051 m3 mol−1, while the Gt was enhanced in the range of 34.74 × 106 - 35.8803 × 106 kJ m−3 as the ZrO2 content increased. Young's modulus changed from 25.7637 to 21.8953 GPa. At the same time, the shear modulus was found to change from 11.4460 to 10.4782 GPa. The bulk modulus varied from 11.464 to 8.0167 GPa; the longitudinal modulus varied from 26.7255 to 21.9877 GPa. The values of Poisson's ratio were found to change from 0.1254 to 0.0448. The electrical results revealed that the addition of ZrO2 minimized the electrical conductivity in the temperature range of 20–300 °C; besides, it maximized the activation energy.

Investigation of mechanical features and gamma-ray shielding efficiency of ternary TeO2-based glass systems containing Li2O, Na2O, K2O, or ZnO

Mechanical features and gamma-ray shielding competence of four ternary TeO2−based glass systems with the form of 80TeO2–10Li2O–10BaO (S1), 80TeO2–10Na2O–10BaO (S2), 80TeO2–10K2O–10BaO (S3), and 80TeO2–10Na2O–10ZnO (S4) were evaluated. The mechanical parameters were estimated via Makishima–Mackenzie's (M-M) model, while the gamma-ray shielding parameters were evaluated via the Monte Carlo method (Geant4) and the theoretical calculation (Phy-X/PSD). The results of these two methods were in good agreement. The results showed that the ionic packing density (Vt) was observed in the order of 0.504, 0.496, 0.495, and 0.499 (m3/mol) for S1, S2, S3, and S4 glasses, respectively. The total dissociation energy (Gt) varied from 54.94 × 106 (KJ/m3) for S1 glasses to 49.07 × 106 (KJ/m3) for S3 glasses. The maximum elastic properties (Km, Em, Gm, Lm), Poisson's ratio (σm), and hardness (H) were found for S1 glasses, while the minimum was found for S3 glasses. The mass attenuation coefficient (MAC) of the investigated S1–S4 glasses was in the order: (MAC)S1 > (MAC)S3 > (MAC)S2 > (MAC)S4. The LAC arranged according to the order of (LAC)S1 > (LAC)S2 > (LAC)S4 > (LAC)S3. It was found that S1 has the lowest HVL with values from 0.00312 cm (at 15 keV) to 3.428 cm at (15 MeV). Buildup factors for gamma exposure (EBF) and gamma absorption energy (EABF) were also evaluated and discussed in terms of their variation with energy and their variation with penetration depths. Finally, the neutron shielding properties of the investigated glass were estimated for each glass in terms of removal cross section for fast neutrons. The S1 glass was found to own shielding efficiency better than commercial glasses and ordinary concrete.

Mechanical features, alpha particles, photon, proton, and neutron interaction parameters of TeO2–V2O3–MoO3 semiconductor glasses

Mechanical properties, alpha particles, gamma-ray, proton, and neutron interaction parameters of 40TeO2-(60-x)V2O5-xMoO3: 20 ≤ xMoO3 ≤ 60 mol% (TVM20-TVM60) semiconductor glasses have been investigated. Based on Makishima–Mackenzie's model, the total ionic packing density (Vt) and the total dissociation energy (Gt) for TVM-glasses have been computed. Elastic moduli, hardness, and Poisson's ratio haven been calculated. Utilizing WinXcom and EXABCal computer codes, mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half value layer (HVL), mean free path (MFP), effective atomic number (Zeff), equivalent atomic number (Zeq), energy absorption and exposure built up factors (EABF and EBF), and fast neutron removal cross section ∑R have been computed. Results reflected that the (Vt) of the TVM-glasses varied from 0.597 to 0.610 (m3/mol), while the (Gt) increased from 63.36 × 106 to 63.48 × 106 (KJ/m3) for TVM20 to TVM60 glasses. The highest elastic features were found for TVM60 glass sample with highest value of MoO3 content. The elastic properties varied from 75.77 to 77.45 GPa for Young's modulus, from 54.67 to 56.70 GPa for bulk modulus, and from 0.267 to 0.272 for Poisson's ratio. The TVM60 glass sample possess the highest MAC, followed by TVM50, TVM40, TVM30, and TVM20, respectively. The maximum HVL was obtained at 8 MeV for all glass samples with values of 5.75, 5.30, 5.05, 4.71 and 4.31 cm for TVM 20, TVM30, TVM40, TVM50, and TVM60, respectively. The TVM60 has a better fast neutron shielding capacity compare to the other glasses. The relative difference between EABF and EBF of the glasses were in the order TVM20 > TVM30 > TVM40 > TVM50 > TVM60. We can say that TVM60 glass can attenuate more photons than TVM20-TVM50 glasses.

Effect of Tungsten on Physical and Optical Properties of Niobate Tellurite Glasses

In the present work, three optically transparent tungsten niobate tellurite glasses with compositions of (90-x)TeO2-10Nb2O5-xWO3 (x = 0, 6, 12 mol%) were synthesized by conventional melt quenching technique. For all these three glass samples, the structural and the compositional dependence of different physical parameters such as density, molar volume and ionic packing density have been analyzed. It been observed that the amorphous nature of the samples has been confirm by X-ray diffraction analysis. The physical properties of the glasses were evaluated and the change in density ( ), molar volume ( ) and ionic packing density ( ) in these glasses indicates the effect of WO3 different content registered on the glasses structure. The highest refractive indexes value 2.171 at 632.8 nm was measured for 78TeO2–10Nb2O5–12WO3 glass. It is found that the addition of WO3 concentration to TeO2-Nb2O5 glass system increase the value of density, molar volume as well as ionic packing density. The refractive index value of the glass increase with tendency for small optical energy band gap.

Role of aluminum on the physical and spectroscopic properties of chromium-doped strontium alumino borate glasses

The glass samples were prepared in accordance with the formula: (30-x)SrO–xAl2O3–69.8B2O3–0.2Cr2O3(0 [Formula: see text]x [Formula: see text] 15 mol %) by melt quenching method. The absence of Bragg’s peaks confirmed the amorphous nature of the prepared glass samples. It was observed that the molar volume was increasing while the density is decreasing with increasing of Al2O3content. Optical absorption study was performed to evaluate the optical bandgap, oxygen packing density, ionic packing density and Urbach energies. The Racah parameters (B and C) and D[Formula: see text]/B ratio have been calculated. Fourier transform infrared (FTIR) spectra recorded in the region from 400–1600 cm[Formula: see text] at room-temperature (RT) confirmed the formation of BO3, BO4and AlO4groups upon the addition of strontium oxide as modifier. The Raman spectra of all the glasses recorded over continuous spectral range 200–1600 cm[Formula: see text] exhibited different spectral bands. The EPR spectra recorded at 9.7 GHz (X-band frequency) have four resonance signals. The signal at g [Formula: see text] 5.33 is due to Cr[Formula: see text] ion sites of rhombic symmetry and signal at g [Formula: see text] 1.97 is due to contribution from Cr[Formula: see text] and Cr[Formula: see text] ion pairs.

Hardness and Structure of Er<sup>3+</sup>:Sm<sup>3+</sup> Co-Doped Oxychloride Zinc Tellurite Glass

Glass samples with composition of (64-x)TeO2 + (x)ZnO + 15 ZnCl2 + 0.5 Sm2O3 + 0.5 Er2O3 (x = 20, 25 and 30 mol%) are prepared by melt quenching method. The season for co-doping with rare earth ions such as samarium (Sm3+) and erbium (Er3+) is to explore the feasibility of their simultaneous exploitation as high performing up-converted lasing materials. The role of varying modifier of ZnO concentration in improving the hardness and structural properties are evaluated. The density is observed to reduce and ionic packing density is augmented with increasing concentration of ZnO. Glass with 25 mol% of ZnO revealed the optimum hardness of 2830 N/mm2. Incorporation of Zn2+ into the tellurite host matrix is found to shift the IR bands position slightly without altering their intensity. Bonding vibrations corresponding to bending of TeO3 unit (784-762 cm-1), stretching of TeO4 units (678-676 cm-1) and Zn-O bonds (462-452 cm-1) are evidenced. Incorporation of ZnO as modifier is established to enhance the hardness and improved the structural properties. The proposed glass composition may be useful for industrial purposes.

Structural and Thermal Behavior of Sm3+ Ions Doped Sodium Tellutite Glasses

The effect of Sm +3 ions concentration doped TeO 2 -Na 2 O glasses on structural and thermal parameters have been discussed. Glass samples with molar composition (80- x ) TeO 2 -20Na 2 O- x Sm 2 O 3 glasses ( x =0, 0.3, 0.6, 1, 1.2, 1.5) are prepared by melt quenching technique. Crystallization temperature ( T c ) , melting temperature ( T m ) and glass transition temperature ( T g ) are measured by using differential thermal analysis (DTA), it is found that the stability factor ( ΔT ) increases from (58.5-97.8) oC with the increasing of Sm 2 O 3 . The amorphous phase nature of the glass samples are observed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectrometer are applied to study the structural properties of the glass samples. Values of density ( ρ ), molar volume ( V M ), and ionic packing density ( V t ) were calculated for each of the glass compositions. The effect of the Sm 2 O 3 on the glass structure have been investigated by using FTIR and Raman spectroscopies, the FTIR spectra are characterized by a band of 637 cm -1 for the telluride glass, high frequency peak at 668 cm -1 presented by Raman spectra which indicates that these glasses network are basically consists of TeO 4 and TeO 3 /TeO 3+1 structural units. The spectra of Raman shows the presence of Sm-O bond, Na-O bond, Te-O-Te bridging configurations, vibrations of Te-O-Te bonds and stretching modes of non-bonding oxygen found on the TeO 3 /TeO 3+1 structural unit.

Effect of AgCl NPs: Physical, thermal, absorption and luminescence properties

Silver nanoparticles (AgCl NPs) are embedded in Er3+/Nd3+ co-doped lithium niobate tellurite glasses of the form (68-x)TeO2-15Li2CO3-15Nb2O5-1Er2O3-1Nd2O3-(x)AgCl with x = 1,2 and 3 mol% via conventional melt-quenching technique. The physical properties such as density, ionic packing density, refractive index and electronic polarizability are computed utilizing the usual method. The existence of AgCl NPs with an average size of 3.7 nm is confirmed using TEM analysis. Moreover, the thermal stability and Hruby criterion of the glass decreases as the AgCl NPs content increases. The direct optical band gap are found decrease as the AgCl NPs content increase, but both indirect optical band gap and Urbach energy are found increases as AgCl NPs content increases. The luminescence spectra shows two strong emission which is the purple emission at 436 nm and red emission at 724 nm which also been observed has strong quenching due to the AgCl NPs, Er3+/Nd3+ dopant and modifier, lithium niobate which possessed magnetic penetration. These glass compositions may be potential for various applications such as solid state devices including laser.

Ionic Strength, Surface Charge, and Packing Density Effects on the Properties of Peptide Self-Assembled Monolayers.

The various environmental parameters of packing density, ionic strength, and solution charge were examined for their effects on the properties of the immobilized peptide mimotope CH19 (CGSGSGSQLGPYELWELSH) that binds with the therapeutic antibody Trastuzumab (Herceptin) on a gold substrate. The immobilization of CH19 onto gold was examined with a quartz crystal microbalance (QCM). The QCM data showed the presence of intermolecular interactions resulting in the increase of viscoelastic properties of the peptide self-assembled monolayer (SAM). The CH19 SAM was diluted with CS7 (CGSGSGS) to decrease the packing density as CH19/CS7. The packing density and ionic strength parameters were evaluated by atomic force microscopy (AFM), ellipsometry, and QCM. AFM and ellipsometry showed a distinct conformational difference between CH19 and CH19/CS7, indicating a relationship between packing density and conformational state of the immobilized peptide. The CH19 SAM thickness was 40 Å with a rough topology, while the CH19/CS7 SAM thickness was 20 Å with a smooth topology. The affinity studies showed that the affinity of CH19 and CH19/CS7 to Trastuzumab were both on the order of 107 M-1 in undiluted PBS buffer, while the dilution of the buffer by 1000× increased both SAMs affinities to Trastuzumab to the order of 1015 M-2 and changed the binding behavior from noncooperative to cooperative binding. This indicated that ionic strength had a more pronounced effect on binding properties of the CH19 SAM than packing density. Electrochemical impedance spectroscopy (EIS) was conducted on the CH19/CS7 SAM, which showed an increase in impedance after each EIS measurement cycle. Cyclic voltammetry on the CH19/CS7 SAM decreased impedance to near initial values. The impact of the packing density, buffer ionic strength, and local charge perturbation of the peptide SAM properties was interpreted based on the titratable sites in CH19 that could participate in the proton transfer and water equilibrium.

A basic insight on structural modification of manganese oxide nanoparticles included borotellurite glass with europium impurities

This paper reports the Manganese oxide nanoparticles (Mn3O4 NPs) concentration dependent structural modification of europium (Eu3+) doped borotellurite glass. Series of glass samples with chemical composition (59-x)TeO2-30B2O3-10MgO-1Eu2O3-xMn3O4 (0.0≤x≤2.0mol%) are synthesized using melt quenching method. Prepared samples are thoroughly characterized using various spectroscopic and imaging techniques. XRD pattern confirmed the samples amorphous phase and DTA results verified their thermal stability. Glass containing 1.0mol% of NPs exhibited highest thermal stability. Influence of NPs contents on the physical properties including density, molar volume, ionic packing density, optical basicity, bonding parameters and oxygen packing density are evaluated. Mn3O4 NPs revealed two surface plasmon resonance bands positioned at 388nm and 516nm. FTIR and Raman spectra displayed NPs assisted alteration in the TeOTe, BO3, BO4, TeO3 trigonal pyramidal and TeO4 trigonal bipyramidal bonding vibrations. TEM image manifested the nucleation of NPs with mean diameter ~15±1nm. HRTEM data authenticated the growth of such NPs along (103) lattice plane having 0.276nm spacing. The Mn3O4 NPs mediated modification in the overall structural properties is explained in terms of symmetry, generation of non-bridging oxygen atoms and effects of covalency. This new glass composition may generate renewed interests towards the development of functional glass useful for magneto-optic applications.

Influence of CuO and Al2O3 addition on the optical properties of sodium zinc phosphate glass absorption filters

The phosphate glasses having chemical composition of 45P2O5-(35-y)ZnO-(20-x)Na2O-xCuO-yAl2O3 (0≤x≤5, 0≤y≤4) have been prepared using the melt quenching technique. XRD analysis has been carried out on the investigated samples in order for confirming the amorphous nature. The density has been measured using Archimedes method and then the molar volume has been calculated. It is found that the density, unlike molar volume, increases with increasing CuO content. This is due to the difference in atomic weight between Cu and Na. Addition of Al2O3 causes a slight decrease in density and a large increase in molar volume. The ionic concentration, inter ionic distance and oxygen packing density have been calculated for all investigated glasses. Using optical absorption, the optical bandgap has been calculated and found to decrease with increasing CuO concentration. This decrease becomes slower in the presence of Al2O3 which makes an increase in the bandgap at the the absence of CuO. The transmission spectrum of the investigated glasses shows that the samples containing CuO behave as bandpass filters. the characterized parameters of these filters, i.e. area, center, width, height and full wave half maximum (FWHM) of bandpass, have been estimated. These parameters have been found to be more affected by CuO and Al2O3 addition. The refractive index, extinction coefficient, real and imaginary part of the dielectric constant have also been calculated at the bandpass.

Effect of Sm<sup>3+</sup> Concentration on Physical Properties of Magnesium Tellurite Glasses Containing Silver Nanoparticles

A series of tellurite glass containing samarium ion and silver nanoparticles with a composition of (89.6-x)TeO2-10MgO-(x)Sm2O3-0.4AgCl with 0.2 ≤ x ≤ 1.0mol% have been synthesized by a conventional melt quenching technique. The X-ray diffraction pattern verified the amorphous nature of glasses. A systematic study on the relationship between Sm2O3 concentration and the physical properties of the glass has been made. The effect on the progressive replacement of TeO2 by Sm2O3 on density, molar volume, refractive index and electronic polarisability has been investigated. The results show that density and ionic packing density are in the range of 4.91-5.04 g cm-3 and 0.444 – 0.455, respectively, increases as the amount of Sm2O3 is increased up to 0.8 mol% and decrease afterward. However, the molar volume which is in between, 29.59-30.26 m3 mol-1 decreasing as the amount of Sm2O3 is increased up to 0.8 mol% and increase thereafter. Meanwhile the refractive index which is deduced from optical energy band gap is found to possess a value in the range of 2.37 to 2.45 and electronic polarisability is in the range of 7.14-7.51Å3. All the results will be discussed with respect to the glass composition.

Influence of Sm2O3 Ion Concentration on Structural and Thermal Modification of TeO2-Na2O Glasses

The effect of Sm+3 ions concentration doped TeO2-Na2O glasses on structural and thermal parameters have been discussed. Glass samples with molar composition (80-x) TeO2-20Na2O-xSm2O3 glasses (x=0, 0.3, 0.6, 1, 1.2, 1.5) are prepared by melt quenching technique. Crystallization temperature (Tc), melting temperature (Tm) and glass transition temperature (Tg) are measured by using differential thermal analysis (DTA), it is found that the stability factor (ΔT) increases from (58.5-97.8) oC with the increasing of Sm2O3. The amorphous phase nature of the glass samples are observed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectrometer are applied to study the structural properties of the glass samples. Values of density (ρ), molar volume (VM), and ionic packing density (Vt) were calculated for each of the glass compositions. The effect of the Sm2O3 on the glass structure have been investigated by using FTIR and Raman spectroscopies, the FTIR spectra are characterized by a band of 637 cm-1 for the telluride glass, high frequency peak at 668 cm-1 presented by Raman spectra which indicates that these glasses network are basically consists of TeO4 and TeO3/TeO3+1 structural units. The spectra of Raman shows the presence of Sm-O bond, Na-O bond, Te-O-Te bridging configurations, vibrations of Te-O-Te bonds and stretching modes of non-bonding oxygen found on the TeO3/TeO3+1 structural unit.

Physical and absorption properties of titanium nanoparticles incorporated into zinc magnesium phosphate glass

We report the influences of Titania (TiO2) nanoparticles (NPs) on the physical and optical properties of melt quench synthesized zinc magnesium phosphate glasses. Five glass samples with composition (42−x)P2O5–50ZnO–8MgO–xTiO2, where x=0, 1, 2, 3, 4mol% are prepared and characterized. XRD pattern verified the amorphous nature of all samples. TEM images manifested the growth of Ti NPs of average size≈5.78nm. TiO2 NP concentration dependent variation in the physical properties including glass density, molar volume, molar refractivity, electronic polarizability and ionic packing density are determined. The values of glass refractive indices, density and ionic packing density are increased with the increase of TiO2 NP contents. Conversely, the Urbach energy, direct and indirect optical band gap are found to decrease with the increase of TiO2 NP concentration. These glass compositions may be potential for various solid state devices including laser.

Effect of silver nanoparticles incorporated with samarium-doped magnesium tellurite glasses

Silver nanoparticles (Ag NPs) are incorporated in samarium doped tellurite glass of a composition (89−x)TeO2–10MgO–1Sm2O3–xAgCl, where 0.0≤x≤0.6mol%, by a melt quenching technique. It is found that all the glasses are amorphous in nature, and the existence of Ag NPs with an average size of 16.94nm is confirmed by Transmission Electron Microscopy. Meanwhile, their physical properties such as glass density, molar volume and ionic packing density are computed utilizing the normal method. The density and ionic packing density are observed to decrease with increasing Ag NPs, but increase when the Ag NPs are beyond 0.2mol%. On the other hand, the molar volume behaves exactly opposite to the increase in Ag NPs content. It decreases when the Ag NPs content value is more than 0.2mol%. The optical energy band gap and Urbach energy are evaluated from the absorption spectra in the range of 200–900nm at room temperature. It is also observed that the direct and indirect optical energy band gaps reduce with Ag NPs content, but enhance when the Ag NPs are beyond 0.2mol%. Meanwhile, the Urbach energy is found to increase as the Ag NPs content is increased but decreases when Ag NPs is 0.2mol%. The refractive index is deduced from indirect optical energy band gap. Meanwhile, molar refraction and electronic polarizability have been calculated from the Lorentz–Lorentz relation. Refractive index and electronic polarizability are also observed to raise with Ag NPs content, but drop off when Ag NPs content is more than 0.2mol%. In this paper, all properties are discussed with respect to the Ag NPs concentration.

Physical and optical properties of zinc arsenic tellurite glasses

Glasses in the system xZnF2–(20−x)ZnO–40As2O3–40TeO2 (x=0, 4, 8, 12, 16 and 20mol%) were prepared by normal melt quenching method. The change in density and ionic packing density in these glasses indicates the effect of ZnF2 on the glass structure. The optical constants of these glasses are determined over a spectral range, providing the complex dielectric constant to be calculated. The values of the optical band gap Eg for all types of electronic transitions and refractive index have been determined and discussed. The optical parameters such as N/m∗, ε∞, ωp, Ed and E0 have been estimated. The values of N/m∗ reflect an increase in the free carrier concentration with increasing ZnF2 content. This leads to an increase in the reflectance, R which in turn increases the refractive index.

Calorimetric Investigation of Tricritical Behavior in Tetragonal Pb(ZrxTi1−x)O3

The order of the cubic ↔ tetragonal phase change in ferroelectric Pb(ZrxTi1−x)O3(PZT) was investigated by measurements of the specific heat. The specimens studied were highly crystalline powder samples carefully prepared by chemical synthesis methods to ensure chemical homogeneity. The existence of a tricritical point in the compositional range 0.30≤x≤0.40 was established. The results demonstrated a close correspondence between the effects of hydrostatic pressure and the effects of zirconium substitution on the order of the transition. A relationship between the first-order character of the transition and the ionic packing density in the cubic structure was proposed.