Oxygen ionic transport in SrFe1−yAlyO3−δ and Sr1−xCaxFe0.5Al0.5O3−δ ceramics

The oxygen permeability of mixed-conducting Sr_1−xCa_xFe_1−yAl_yO_3−δ (x=0–1.0; y=0.3–0.5) ceramics at 850–1000 °C, with an apparent activation energy of 120–206 kJ/mol, is mainly limited by the bulk ionic conduction. When the membrane thickness is 1.0 mm, the oxygen permeation fluxes under pO₂ gradient of 0.21/0.021 atm vary from 3.7×10⁻¹⁰ mol s⁻¹ cm⁻² to 1.5×10⁻⁷ mol s⁻¹ cm⁻² at 950 °C. The maximum solubility of Al³⁺ cations in the perovskite lattice of SrFe_1−yAl_yO_3−δ is approximately 40%, whilst the brownmillerite-type solid solution formation range in Sr_1−xCa_xFe_0.5Al_0.5O_3−δ system corresponds to x>0.75. The oxygen ionic conductivity of SrFeO₃-based perovskites decreases moderately on Al doping, but is 100–300 times higher than that of brownmillerites derived from CaFe_0.5Al_0.5O_2.5+δ. Temperature-activated character and relatively low values of hole mobility in SrFe_0.7Al_0.3O_3−δ, estimated from the total conductivity and Seebeck coefficient data, suggest a small-polaron mechanism of p-type electronic conduction under oxidising conditions. Reducing oxygen partial pressure results in increasing ionic conductivity and in the transition from dominant p- to n-type electronic transport, followed by decomposition. The low-pO₂ stability limits of Sr_1−xCa_xFe_1−yAl_yO_3−δ seem essentially independent of composition, varying between that of LaFeO_3−δ and the Fe/Fe_1−γO boundary. Thermal expansion coefficients of Sr_1−xCa_xFe_1−yAl_yO_3−δ ceramics in air are 9×10⁻⁶ K⁻¹ to 16×10⁻⁶ K⁻¹ at 100–650 °C and 12×10⁻⁶ K⁻¹ to 24×10⁻⁶ K⁻¹ at 650–950 °C. Doping of SrFe_1−yAl_yO_3−δ with aluminum decreases thermal expansion due to decreasing oxygen nonstoichiometry variations.     

Effect of gallium addition on physical and structural properties of Ge–S chalcogenide glasses

GeS_2.5 chalcogenide glass was selected for studying effects of Ga addition on physical and structural properties. Glassy and partially crystallized samples of (100−x)GeS_2.5−xGa (5 mol% ≤ x ≤ 40 mol%) were prepared, and their thermal and optical properties were characterized. With increasing Ga content (x), values of T_g and optical band gap of glasses initially increased and then decreased, showing a maximal value at x = 25 mol%, that is, with stoichiometric composition of 85.7GeS₂·14.3Ga₂S₃. These changes were discussed and correlated to evolution of network structure, which was investigated by Raman spectra recorded in glassy matrices of (100−x)GeS_2.5−xGa (5 mol% ≤ x ≤ 40 mol%). This work contributes to understanding of composition–structure–property relationship of chalcogenide glasses.     

Colossal dielectric permittivity and electrical properties of the grain boundary of Ca1−3x/2YbxCu3−yMgyTi4O12 (x=0.05, y=0.05 and 0.30)

Dielectric properties of Ca_1−3x/2Yb_xCu_3−yMg_yTi₄O₁₂ (x=0.05, y=0.05 and 0.30) prepared using a modified sol–gel method and sintered at 1070 °C for 4 h were investigated. The mean grain sizes of the CaCu₃Ti₄O₁₂ and co-doped Ca_0.925Yb_0.05Cu_3−yMg_yTi₄O₁₂ (y=0.05 and 0.30) ceramics were ≈15.86, ≈3.37, and ≈2.32 μm, respectively. Interestingly, the dielectric properties can be effectively improved by co-doping with Yb³⁺ and Mg²⁺ ions to simultaneously control the microstructure and properties of grain boundaries, respectively. These properties were improved over those of single-doped and un-doped CaCu₃Ti₄O₁₂ ceramics. A highly frequency−independent colossal dielectric permittivity (≈10⁴) in the range of 10²–10⁶ Hz with very low loss tangent values of 0.018–0.028 at 1 kHz were successfully achieved in the co-doped Ca_0.925Yb_0.05Cu_3−yMg_yTi₄O₁₂ ceramics. Furthermore, the temperature stability of the colossal dielectric response of Ca_1−3x/2Yb_xCu_3−yMg_yTi₄O₁₂ was also improved to values of less than ±15% in the temperature range from −70 to 100 °C.     

Microstructures and electrical properties of lead zinc niobate–lead titanate–lead zirconate ceramics using microwave sintering

Electrical properties and microstructural characteristics of (1 − x)(0.94PbZn_1/3Nb_2/3O₃ + 0.06BaTiO₃) + xPbZr_yTi_1−yO₃ (PZN–PZ–PT) ceramics, sintered by microwave heating, were investigated using electron microscopy, energy-dispersive spectroscopy (EDS) and electrical property measurement. Experimental results imply that the microwave-sintered (MW) samples with x = 0.5 and y = 0.52 (1150 °C, 10 min) possess higher dielectric constant than the conventionally sintered (CS) specimens (1150 °C, 2 h). Microstructural investigations show that ZnO precipitated on the surfaces of specimens during a thermal process, implying that ZnO diffusion may have influenced the distribution of phases in a specimen due to an eutectic reaction of PbO and ZnO. TEM–EDS investigations show that the CS specimens exhibit pronounced elemental segregation of PbO and ZnO at the grain boundaries, but it is much less significant for MW samples. The results imply that microwave sintering not only enhances material densification markedly, but also reduces the PbO/ZnO segregation and amorphous intergranular layers effectively, and thus improve the electrical properties of PZN–PZ–PT ceramics.     

Gel-derived SiO2–CaO–P2O5 bioactive glasses and glass-ceramics modified by SrO addition

The effect of SrO substitution for CaO in two sol–gel glasses with different chemical compositions (mol%) A2Sr: (54−x)CaO–xSrO–6P₂O₅–40SiO₂ and S2Sr: (16−x)CaO–xSrO–4P₂O₅–80SiO₂ (x=0, 1, 3 and 5) stabilized at 700 °C on their structure (XRD, FTIR) and bioactive properties (SBF test) was investigated. Preliminary in vitro tests using human articular chondrocytes of selected A2Sr glass were also conducted. Moreover, the subject of this study was to detect the changes on material properties after heat treatment at 1300 °C. The results show that the effect of strontium substitution on structure, bioactivity and crystallization after treatment at both the above temperatures strongly depends on CaO/SiO₂ molar ratio. The presence of 3–5 mol% of strontium ions creates more expanded glass structure but does not markedly affect crystallization ability after low temperature treatment. Sintering at 1300 °C of A2 type glasses results in crystallization of pseudowollastonite, hydroxyapatite and also Sr-substituted hydroxyapatite for 3–5 mol% of SrO substitution. The increase of strontium concentration in silica-rich materials after sintering leads to appearance of calcium strontium phosphate instead of calcium phosphate. Bioactivity evaluation indicates that substitution of Sr for Ca delays calcium phosphate formation on the materials surface only in the case of silica-rich glasses treated at 700 °C. Calcium-rich glasses, after both temperature treatments, reveals high bioactivity, while crystal size of hydroxyapatite decreases with increasing Sr content. High temperature treatment of high-silica glasses inhibits their bioactivity. Preliminary in vitro tests shows Sr addition to have a positive effects on human articular chondrocytes proliferation and to inhibit cell matrix biomineralization.     

Synthesis,structure and oxygen thermally programmed desorption spectra of La1−xCaxAlyFe1−yO3−δ perovskites

Perovskites La_1−xCa_xAl_yFe_1−yO_3−δ (x, y = 0 to 1) were prepared by high-temperature solid-state synthesis based on mixtures of oxides produced by colloidal milling. The XRD analysis showed that perovskites La_0.5Ca_0.5Al_yFe_1−yO_3−δ with a high Fe content (1 − y = 0.8–1.0) were of orthorhombic structure, perovskites with a medium Fe content (1 − y = 0.8–0.5) were of rhombohedral structure, and perovskite with the lowest Fe content (1 − y = 0.2) were of cubic structure. Thermally programmed desorption (TPD) of oxygen revealed that chemical desorption of oxygen in the temperature range from 200 to 1000 °C had proceeded in the two desorption peaks. The low-temperature α-peak (in the 200–550 °C temperature range) was brought about by oxygen liberated from oxygen vacancies; the high-temperature β-peak (in the 550–1000 °C temperature range) corresponded to the reduction of Fe⁴⁺ to Fe³⁺. The chemidesorption oxygen capacity increased with increasing Ca content and decreased with increasing Al content in the perovskites. The Al³⁺ ions restricted, probably for kinetic reasons, the reduction of Fe⁴⁺ and the high-temperature oxygen desorption associated with it.     

Study on luminescence properties of co-doped nanoparticles Gd2O3:Tb3+, Eu3+ synthesized by polyol route

Spherical-like Tb³⁺ and Eu³⁺ co-doped Gd₂O₃ nanoparticles with a particle size around 5.5 nm were synthesized by a polyol route. The optimized luminescence property was obtained when 5 mol% Tb³⁺ and 2 mol% Eu³⁺ were co-doped. The influence of different polyalcohol solvents (DEG/PEG) on particle size and luminescence properties was investigated. The results show that the nanoparticles Gd₂O₃:5%Tb³⁺ prepared in PEG presented greater particle size (around 79 nm) and higher luminescence intensity.     

High-temperature thermoelectric properties of polycrystalline Zn1−x−yAlxTiyO ceramics

The as-sintered Zn_1−xAl_xO (0 ≤ x ≤ 0.05) samples crystallized in the ZnO with a wurtzite structure, along with a small amount of the cubic spinel ZnAl₂O₄. The addition of Al₂O₃ to ZnO gave rise to a decrease in grain size, ranging from 7.3 to 2.7 μm and in relative density, ranging from 99.2 to 90.1% of the theoretical density. In the Zn_0.97Al_0.03−yTi_yO samples, as the amount of TiO₂ increased, the grain size of ZnO grains and second phases, such as Zn₂TiO₄ and ZnAl₂O₄, as well as density increased. The co-doping of Al and Ti led to a significant increase in both the electrical conductivity and the absolute value of the Seebeck coefficient, resulting in an increase in the power factor. The highest value of power factor (3.8 × 10⁻⁴ W m⁻¹ K⁻²) was attained for Zn_0.97Al_0.02Ti_0.01O at 800 °C. It is demonstrated that the Al and Ti co-doping is fairly effective for enhancing thermoelectric properties.     

White emitting Dy3+ activated perovskite titanates and energy transfer by Eu3+ codoping

Perovskite type titanate phosphors Sr_0.97−xDy_0.03Li_xTi_1−xNb_xO₃, Sr_0.9−xDy_xLi_0.1Ti_0.9Nb_0.1O₃ and Sr_0.87−yDy_0.03Eu_yLi_0.1Ti_0.9Nb_0.1O₃ were prepared by conventional solid state method. Herein, white light emission from Sr_0.9−xDy_xLi_0.1Ti_0.9Nb_0.1O₃ phosphors and the lowering of its color temperature through codoping with Eu³⁺ ions are reported. Raman measurements have shown that the incorporation of dopants alters the vibrational properties of these phosphors significantly, indicating the reduction of the local symmetry in the crystal lattice. The addition of LiNbO₃ in SrTiO₃:Dy³⁺ phosphor enhances the luminescence intensity and the yellow to blue ratio resulting in emission of high quality white light with color coordinates corresponding to that of standard white. Life time measurements and data fits of Sr_0.9−xDy_xLi_0.1Ti_0.9Nb_0.1O₃ phosphors revealed the biexponential behaviour of luminescence decay profiles. From Judd-Ofelt analysis it is found that the intensity parameter Ω₂ increases with Dy³⁺ concentration and a quantum efficiency of 90.4% was obtained for optimum concentration. In the case of Dy³⁺ and Eu³⁺ codoped phosphors, the color coordinates are found to be sensitive to the Eu³⁺ concentration and the highest energy transfer efficiency of 92% was obtained for the phosphor doped with 10 mol% Eu³⁺. The emission color changes from cold white to reddish orange when the wavelength of excitation alters from 452 to 388 nm, since the energy transfer mechanism alone take place under 452 nm excitation and both direct absorption and the energy transfer mechanism occurs under 388 nm excitation.     

Elastic properties of quaternaryTeO2–ZnO–Nb2O5–Gd2O3 glasses

Tellurite glass systems in the form 75TeO₂–15ZnO–(10−x)Nb₂O₅–xGd₂O₃ (x=0.0, 0.5, 1.0, 1.5, 2.0, 2.5 mol%) have been prepared by the melt quenching technique. Both longitudinal and shear ultrasonic velocities were measured by using the pulse-echo method at 5 MHz frequency and at room temperature. Elastic moduli (longitudinal modulus, shear modulus, Young׳s modulus, Bulk modulus), Poisson׳s ratio, Debye temperature, micro-hardness and softening temperature have been calculated. Quantitative analysis of elastic moduli based on the number of bond per unit volume, average crosslink and number of vibrating atoms per unit volume has been achieved.     

Photoluminescence and electron-beam excitation induced cathodoluminescence properties of novel green-emitting Ba4La6O(SiO4)6:Tb3+phosphors

Tb³⁺ions activated Ba₄La₆O(SiO₄)₆ (BLSO:Tb³⁺) phosphors were synthesized by a citrate sol-gel method. The X-ray diffraction pattern confirmed their oxyapatite structure. The field-emission scanning electron microscope image established that the BLSO:Tb³⁺phosphor particles were closely-packed and acquired irregular shapes. The photoluminescence (PL) excitation spectra of BLSO:Tb³⁺phosphors showed intense f–d transitions along with low intense peaks corresponding to the f–f transitions of Tb³⁺ions in the lower energy region. The PL emission spectra displayed the characteristic emission bands of Tb³⁺ions, and the optimized concentrations were found to be at 1 and 6 mol% for blue and green emission peaks, respectively. The cathodoluminescece (CL) spectra exhibited a similar behavior that was observed in the PL spectra except the intensity variations in the blue and green regions. The CL spectra of the BLSO:6 mol% Tb³⁺phosphor unveiled accelerating voltage induced luminescent properties.     

Electronic conductivity,oxygen permeability and thermal expansion of Sr0.7Ce0.3Mn1−xAlxO3−δ

The maximum solubility of aluminum cations in the perovskite lattice of Sr_0.7Ce_0.3Mn_1−xAl_xO_3−δ is approximately 15%. The incorporation of Al³⁺ increases oxygen ionic transport due to increasing oxygen nonstoichiometry, and decreases the tetragonal unit cell volume and thermal expansion at temperatures above 600 °C. The total conductivity of Sr_0.7Ce_0.3Mn_1−xAl_xO_3−δ (x = 0–0.2), predominantly electronic, decreases with aluminum additions and has an activation energy of 10.2–10.9 kJ/mol at 350–850 °C. Analysis of the electronic conduction and Seebeck coefficient of Sr_0.7Ce_0.3Mn_0.9Al_0.1O_3−δ, measured in the oxygen partial pressure range from 10⁻¹⁸ to 0.5 atm at 700–950 °C, revealed trends characteristic of broad-band semiconductors, such as temperature-independent mobility. The temperature dependence of the charge carrier concentration is weak, but exhibits a tendency to thermal excitation, whilst oxygen losses from the lattice have an opposite effect. The role of the latter factor becomes significant at temperatures above 800 °C and on reducing p(O₂) below 10⁻⁴ to 10⁻² atm. The oxygen permeability of dense Sr_0.7Ce_0.3Mn_1−xAl_xO_3−δ (x = 0–0.2) membranes, limited by both bulk ionic conduction and surface exchange, is substantially higher than that of (La, Sr)MnO₃-based materials used for solid oxide fuel cell cathodes. The average thermal expansion coefficients of Sr_0.7Ce_0.3Mn_1−xAl_xO_3−δ ceramics in air are (10.8–11.8) × 10⁻⁶ K⁻¹.     

Temperature-independent permittivity of xBaTiO3–(1−x)(0.5Bi(Mg1/2Ti1/2)O3–0.5BiScO3) ceramics

xBaTiO₃–(1−x)(0.5Bi(Mg_1/2Ti_1/2)O₃-0.5BiScO₃) or xBT–(1−x)(0.5BMT–0.5BS) (x=0.45–0.60) ceramics were prepared by using the conventional mixed oxide method. Perovskite structure with pseudo-cubic symmetry was observed in all the compositions. Dielectric measurement results indicated that all the samples showed dielectric relaxation behavior. As the content BaTiO₃ was decreased from 0.60 to 0.45, temperature coefficient of permittivity (TCε) in the range of 200–400 °C was improved from −706 to −152 ppm/°C, while the permittivity at 400 °C was increased from 1208 to 1613. The temperature stability of permittivity was further improved by using 2 mol% Ba-deficiency. It was found that lattice parameter and grain size of the 2 mol% Ba-deficient ceramics were smaller than those of their corresponding stoichiometric (S) counterparts, with TCε in the range of 200–400 °C to be improved noticeably. For example, TCε of the Ba-deficiency sample with x=0.45 was −75 ppm/°C in the temperature range of 200–400 °C and the permittivity was 1567 at 400 °C. The results obtained in this work indicated that xBT–(1−x)(0.5BMT–0.5BS) ceramics are very promising candidates for high temperature capacitor applications.     

Structural,electrical, dielectric and magnetic behavior of Gd1−xBixFe1−yZryO3 nanoparticles for advanced technological applications

Gd_1−xBi_xFe_1−yZr_yO₃ nanoparticles were synthesized via micro-emulsion route with different molar concentrations of Bi⁺³ (x) and Zr⁺⁴ (y). The values of x and y were kept in the range 0.00, 0.15, 0.30, 0.45 and 0.60. The characterizations were done by the thermo-gravimetric analysis (TGA), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The average particle size was ~50 nm. The effect of Bi³⁺ and Zr⁴⁺ contents on electrical, dielectric and magnetic parameters were studied. The DC resistivity measurements showed at certain Bi³⁺ and Zr⁴⁺ contents, more than two fold increase in electrical resistivity from 68×10⁸ Ω cm to 150×10⁸ Ω cm. The magnetic measurements showed the paramagnetic nature of Gd_1−xBi_xFe_1−yZr_yO₃ nanoparticles. The electrical and magnetic properties of these nanoparticles suggested that these materials are potential candidates for the fabrication of telecommunication and switching devices.     

Preparation and ionic conduction of CaZr1−xScxO3−α ceramics

A series of CaZr_1−xSc_xO_3−α (x=0, 0.05, 0.10, 0.15) perovskite oxide ceramics were successfully fabricated at 1400 °C for 10 h and then further sintered at 1650 °C for 10 h via a solid-state reaction sintering process. Conductivities of the ceramics were measured under the atmosphere that contains 1% H₂/Ar and 5.63 kPa H₂O/Ar by the electrochemical impedance spectra technique. It was found that the conductivities of CaZr_1−xSc_xO_3−α (x=0, 0.05, 0.10, 0.15) ceramics increased with the increase of the measuring temperature, and the conductivity achieved its maximum value of 2.03×10⁻⁵–6.5×10⁻³ S cm⁻¹ when the doping amount of Sc (x) was 0.10. Additionally, element doping can increase the conductivities and decrease the conductivity activation energies of CaZr_1−xSc_xO_3−α ceramics. The results of transport number measurement indicated that the CaZr_0.9Sc_0.1O_3−α is almost a pure protonic conductor at 500–750 °C, while it is a mixed protonic-oxygen ionic-electronic conductor at 750–1300 °C.     

Effect of Ce and Yb co-doping on conductivity of LaNbO4

La_1−x−yCe_xYb_yNbO₄ specimens with various Ce and Yb contents were prepared by solid reactions, and their crystal structure, element valence, sinterability and conductivity were investigated. LaNbO₄-type single phase was formed at 1200 °C in air, and the lattice of La_1−x−yCe_xYb_yNbO₄ was distorted from that of LaNbO₄ to various extents, depending on the added amount of Ce and Yb. Both La and Nb remained the same valence as they are in LaNbO₄; Ce⁴⁺, Ce³⁺ and Yb³⁺ were detected at room temperature. Highly densified La_1−x−yCe_xYb_yNbO₄ specimens were achieved by sintering at above 1215 °C in air with conductivity 1–2 orders higher than that of pure LaNbO₄ in dry air, wet air and wet 5% H₂–N₂ atmospheres. The conductivity changed with testing atmosphere owing to the competition of electron and proton conduction, and maximal value 4.7 × 10⁻⁴ S cm⁻¹ was obtained in wet air at 900 °C.     

Role of MgO on the HAp forming ability in phosphate based glasses

Phosphate-based glasses 45P₂O₅–30CaO–(25 ? x)Na₂O–xMgO for different compositions of x = 0, 1, 2.5, 5 and 10 mol% were prepared using the normal melt quench technique. To study the influence of MgO on phosphate glasses, a series of experimental analyses such as ultrasonic velocities, differential thermal analysis, X-ray diffraction, energy-dispersive X-ray spectroscopy, pH measurements, Fourier transform infrared spectroscopy, scanning electron microscopy and in vitro studies were carried out in all the prepared glasses. A maxima in ultrasonic parameters at x = 2.5 mol% of MgO content and a further decrease in the same with the addition of MgO content were observed in all glasses. The observed results indicate that structural compactness of glass network took place up to 2.5 mol% of MgO (PCNM2.5), beyond which a loose packing of atoms led to structural softening in glass network. The results obtained from X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy analyses in all glasses before and after in vitro studies revealed the existence of higher HAp-forming ability in PCNM2.5 glass.     

Structural characterization of TiO2–P2O5–CaO glasses by spectroscopy

The structure of glasses with composition x TiO₂·(65 ? x) P₂O₅·35 CaO (x = 0–30 mol%) has been studied and their glass transition temperature, Raman and NMR spectra have been analysed.For TiO₂-free glass two phosphate species have been identified as Q² and Q³. Increasing TiO₂ content in glass compositions results in the disappearance of the Q³ and Q² species and in the formation of, mainly, pyrophosphate structure, Q¹.In calcium titanophosphate glass with higher TiO₂ content the structure consists of a distorted Ti octahedral linked to pyrophosphate unit through P–O–Ti bonds. In these glass series the structural cohesion increases with TiO₂, although a depolymerization in the original P–O–P network occurs.The study of these glasses and the understanding of their structural characteristics can give a valuable contribution for the clarification of their degradation behaviour namely in biological environments.     

Dy3+ doped LiCl–CaO–Bi2O3–B2O3 glasses for WLED applications

Dy³⁺ doped calcium bismuth borate glasses were synthesized in the composition range of xLiCl-(30 − x)CaO-20Bi₂O₃-50B₂O₃ + 1 mol% Dy₂O₃ (x = 0, 2, 5, 7, 10 and 15 mol%, LC0, LC2, LC5, LC7, LC10 and LC15 respectively) using conventional melt-quench technique. Broad XRD profiles confirmed non-crystalline nature of synthesized compositions. The compositional dependencies of structural changes (using FTIR spectra), thermal behavior (using DSC thermographs) and optical band gap (using UV–Vis–NIR spectra) were discussed. Photoluminescence (PL) excitation spectra recorded at 577 nm yielded six different excitation peaks belonging to Dy³⁺ ions. The PL emission spectra recorded at 451 nm were analyzed to extract different light emission parameters viz. Y/B ratio, color coordinates, correlated color temperature (CCT) following CIE 1931 chromaticity diagram. The emission colors were found to lie in white light region and lies very close to standard white light emission. The CCT of sample LC10 (5335 K) is closest to CCT of standard white light (5615 K) which depicted the optimized concentration of LiCl for application of these glasses in WLED application.     

Ionic conductivity of Mn2+ doped dense tin pyrophosphate electrolytes synthesized by a new co-precipitation method

Mn²⁺-doped Sn_1−xMn_xP₂O₇ (x = 0–0.2) are synthesized by a new co-precipitation method using tin(II)oxalate as tin(IV) precursor, which gives pure tin pyrophosphate at 300 °C, as all the reaction by-products are vaporizable at <150 °C. The dopant Mn²⁺ acts as a sintering aid and leads to dense Sn_1−xMn_xP₂O₇ samples on sintering at 1100 °C. Though conductivity of Sn_1−xMn_xP₂O₇ samples in the ambient atmosphere is 10⁻⁹–10⁻⁶ S cm⁻¹ in 300–550 °C range, it increases significantly in humidified (water vapor pressure, pH₂O = 0.12 atm) atmosphere and reaches >10⁻³ S cm⁻¹ in 100–200 °C range. The maximum conductivity is shown by Sn_0.88Mn_0.12P₂O₇ with 9.79 × 10⁻⁶ S cm⁻¹ at 550 °C in ambient air and 2.29 × 10⁻³ S cm⁻¹ at 190 °C in humidified air. It is observed that the humidification of Sn_1−xMn_xP₂O₇ samples is a slow process and its rate increases at higher temperature. The stability of Sn_1−xMn_xP₂O₇ samples is analyzed.