Increase In Ionic Radius Research Articles

Electrical conductivity and viscosity of phosphate glasses and melts

Phosphate glasses are of great interest for basic research and for special applications in various fields as technical and optical glasses. Metaphosphate compositions with PO4-chain structure are mostly used. The cations have a significant effect on the properties of the glasses and melts. This was studied in more details. High purity metaphosphate glasses, Mn(PO3)n with M = Na+, K+, Zn2+, Mg2+, Ca2+, Sr2+, Ba2+, Al3+ and Fe3+, were prepared and the optical and thermal properties were measured with different methods. The electrical conductivity of glasses and melts is the property of great practical importance. It was determined by impedance spectroscopy in a wide temperature range from 300 to 1250 °C in frequency range of 0.1 Hz to 6 MHz. The electrical conductivity of alkaline earth phosphate glasses and melts increases with increasing ion radius of the cation. NaPO3 and KPO3 glasses and melts have much higher conductivity. Viscosity measurements were carried out from transformation temperature, Tg, to the melt. The measured data were fitted and the activation energies of the conductivity and viscosity were calculated. Simple exponential behavior was found at temperatures below Tg, but above Tg only in very narrow temperature range. The relation between conductivity and viscosity was considered.

Scalable lattice-strain in preferentially oriented acceptor-doped cerium oxide film and its impact on oxygen ion transport kinetics

Fast ionic conduction through strain engineered heteroepitaxial film have been demonstrated well. However, this effect in the preferentially orientated film remains to be unexplored. Here, we report the effect of interatomic distance between cation-oxygen bonds on the oxygen ionic transport in preferetially (111) oriented Ce0.80Sm0.1M0.1O2-δ (M = Gd, Nd, Pr, La) film over an amorphous quartz substrate. With the increase in ionic radii of dopant cation, the films exhibited a substantial increase in tensile strain with a change in lattice constant (Δa) in the order of ∼1.14% (Δa: 1.14% (Sm3+ + La3+) > 1.04% (Sm3+ + Pr3+) > 0.69% (Sm3+ + Nd3+) > 0.14% (Sm3+) > 0.08% (Sm3+ + Gd3+)) has strong influence on defect association enthalpy (ΔHa) leading to the change in migration energy of oxygen ion during conduction process. Highest conductivity was observed from Ce0.85Sm0.1Nd0.1O2-δ, which is four times greater than that of Ce0.85Sm0.2O2-δ. As a consequence, it is clear that optimum co-dopant is needed to attain the critical ionic radii/tensile strain to achieve the maximum ionic conductivity in the preferentially oriented ceria-based thin film. This work demonstrates the importance of tuning the ionic radii of dopant cation, which can effectively facilitate the optimum expansion of lattice to attain the fast ionic conduction process in (111) oriented thin film based solid electrolyte.

Electrical and optical properties of four-layered perovskite ferroelectric ABi4Ti4O15 (with A = Sr, Ba, Ca)

In this report, we present the electrical and optical properties of four-layered perovskite ferroelectric ABi4Ti4O15 (with A = Sr, Ba, Ca), prepared by solid-state reaction route. The X-ray diffraction study asserts single-phase orthorhombic structure with A21am space group. Scanning electron microscopy observation shows plate-like grains in all the samples. Notably orthorhombic distortion (b/a) decreases with increase in ionic radius of A-site cation, which was explained by tolerance factor. Additionally, good ferroelectric, piezoelectric, optical and thermal stability obtained in SBT system.

Effect of Rare Earth Ionic Radii on Structural, Electric, Magnetic and Thermoelectric Properties of REMnO3 (RE = Dy, Gd, Eu and Sm) Manganites

In this communication, we present a systematic investigation on structural, electric, magnetic and thermoelectric power properties of REMnO3 (RE = Dy, Gd, Eu and Sm) manganites which were prepared using solid-state reaction route. The samples exhibit orthorhombic crystal structure with Pbnm space group. Rietveld analysis of x-ray diffraction (XRD) data shows that the unit cell volume increases with increase in ionic radii of the rare earth ion, $r_{\text {RE}}$ . The particle size was calculated from the scanning electron microscope (SEM) images. The estimated particle size is observed to decrease with increasing ionic radii of the rare earth ions. All samples exhibit insulating behaviour and display immeasurably high resistivity at low temperatures. Magnetization studies indicate that the samples display a transition in the low temperature region. Magnetization data also reveals that antiferromagnetic behaviour is observed for all samples. Thermoelectric power results show that large thermoelectric power is seen for these manganites. Thermoelectric power of high-temperature region was successfully analysed using small polaron hopping (SPH) model.

Plasma-assisted synthesis of non-stoichiometric nanoceria powder from cerium carbonate hydroxide (CeCO3OH)

Highly non-stoichiometric nanoceria was synthesized for the first time by thermal plasma from the precursor cerium carbonate hydroxide. The particle size was approximately 60 nm according to measurement by TEM. The nanoceria synthesized with 25 kW plasma power with argon as the carrier gas had the largest concentration of oxygen vacancies, follow by that produced with 20 kW with hydrogen as the carrier gas. XRD results indicated that the CeO1.66 phase was present with mostly non-stoichiometric ceria CeO2-x in these two products. SEM and TEM images showed that most of the particles were of irregular shape, while some triangular particles were also present. Raman spectra revealed that the F2g mode of synthesized nanoceria powders had a remarkable downshift of 7.9 - 10.5 cm-1 relative to the peak for single crystal ceria located at 466.0 cm-1. The Raman downshift was explained by the increase in ionic radius upon Ce4+ reduction to Ce3+. XPS results indicated that the Ce3+ content on the surface of the synthesized nanoceria was in the range of 15-30 %, depending on the plasma power and carrier gas composition. Both the Raman and XPS spectra showed numerous oxygen vacancies in the nanoceria. The results of this work indicated that the oxygen vacancy formation occurred when the CeO2 formed from the oxidation of cerium carbonate hydroxide was reduced by the hydrogen as well as the high temperature of the plasma. This investigation has verified that plasma treatment provides a promising method for the synthesis of nanoceria powder with high oxygen vacancies.

Influence of the yttria dopant on the structure and properties of (ZrO2)0.91–x (Sc2O3)0.09(Y2O3) х (x = 0–0.02) crystals

We have studied the influence of the yttrium oxide (Y2O3) dopant (1 and 2 mol %) on the phase composition, structure, and electrical properties of ZrO2–9 mol % Sc2O3 solid solution. Stabilization of ZrO2 jointly with 9 mol % Sc2O3 and 2 mol % Y2O3 is shown to allow the acquisition of high phase stability transparent homogeneous crystals with a cubic structure. Their mechanical grinding is established to cause no change in the phase composition of these crystals, whereas the powders retain the initial fluorine structure. The powders preserved the original structure of the fluorite crystals. All the probed crystals reveal high microhardness and low fracture toughness. Increasing the Y2O3 concentration in the crystals led to a reduction of the maximum loads on the indenter, which the sample withstood without cracking. As is shown, the specific conductivity exhibits nonmonotonic behavior depending on the Y2O3 concentration in the crystals. Increasing the Y2O3 content to 2 mol % in the solid electrolyte reduces the conductivity of the crystals in the entire temperature range that is attributed to a decrease in the carrier mobility due to the increasing ion radius of the stabilizing ion.

How does the spin-state of Co ions affect the insulator-metal transition in Bi2A2Co2O8 (A = Ca, Sr, Ba)?

The misfit layered Bi2A2Co2O8 (A = Ca, Sr, Ba) compounds experience an insulator to metal transition as A’s ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co3+ ions to a hexagonally arranged intermediate-spin low-spin mixed-state in CoO2 plane when ionic radius increases from Ca to Ba. The predicted low-spin state of Bi2Ca2Co2O8 and Bi2Sr2Co2O8 and intermediate-spin low-spin mixed-state of Bi2Ba2Co2O8 are consistent not only with their measured transport properties, but also with the magnetic-field suppressed specific-heat peak observed at the transition temperature. In agreement with experiments, strong electronic correlation is required to stabilize the low-spin insulator and intermediate-spin low-spin metal.

Variation of optical conductivity spectra in the course of bandwidth-controlled metal-insulator transitions in pyrochlore iridates

We spectroscopically investigate a series of pyrochlore iridates ${R}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ ($R$: rare-earth and Y ions) where the metal-insulator transitions are induced by systematic bandwidth control via chemical substitutions of $R$ ions. We establish the phase diagram of ${R}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$, as endorsed by the variation of the optical conductivity spectra, in which the competing phases including paramagnetic insulator (PI), paramagnetic metal (PM), and antiferromagnetic insulator (AFI) show up as a function of bandwidth and temperature. For small $R$-ionic radius ($R=$ Y-Sm), i.e., strongly correlated region, pronounced peaks on the edge of the optical gap are discerned below the magnetic transition temperature ${T}_{\mathrm{N}}$, which is attributable to exciton and magnon sideband absorptions. It turns out that the estimated nearest-neighbor exchange interaction increases as $R$-ionic radius increases, whereas ${T}_{\mathrm{N}}$ monotonically decreases, indicating that the all-in all-out magnetic order arises from the interplay among several exchange interactions inherent to extended $5d$ orbitals on the frustrated lattice. For larger $R$-ionic radius ($R=$ Sm-Pr), i.e., relatively weakly correlated region, the optical conductivity spectra markedly change below 0.3 eV in the course of PM-AFI transition, implying that the magnetic order induces the insulating state. In particular, we have found distinct electrodynamics in the composition of $R=\phantom{\rule{4pt}{0ex}}{\mathrm{Nd}}_{0.5}{\mathrm{Pr}}_{0.5}$ which is located on the boundary of the quantum PM-AFI transition, pointing to the possible emergence of unconventional topological electronic phases related possibly to the correlated Weyl electrons.

Structural and mechanic properties of RFeO3 with R = Y, Eu and La perovskites: a first-principles calculation

The structural and elastic properties of the RFeO3 phases with R = Y, Eu, and La were investigated using first-principles plane-wave pseudopotential density functional theory with the generalized gradient approximation (GGA). The ground state properties (equilibrium cell constants) agree well with the reported experimental results. Our results showed an increase in the unit-cell volume (V) with the increase of ionic radii. We calculate a set of elastic parameters (bulk modulus B VRH , shear modulus G VRH , Young’s modulus E VRH and Poisson’s ratio ν) in the framework of the Voigt-Reuss-Hill (VRH) approximation. The sound velocities (v l , v t ) and Debye temperature (θ D ) were calculated using these elastic moduli. The calculated elastic constants were positives and satisfy the well-known Born criteria, indicating that the orthorhombic structure is stable. Finally, the ratio G VRH /B VRH suggests that the RFeO3 phases are ductile in nature.

Anion sensing and interfering behaviors of electrolyte–insulator–semiconductor sensors with nitrogen plasma-treated samarium oxide

In this article, we demonstrate a samarium oxide (Sm2O3) electrolyte–insulator–semiconductor (EIS) sensor with nitrogen plasma immersion ion implantation (PIII) treatment for anion sensing and interfering characterization. Chloride (Cl−), nitrite (NO2−), and nitrate (NO3−) ions were detected, and the sensitivity was about 49.75 mV/pCl, 53.8 mV/pNO2, and 56.19 mV/pNO3, respectively. Ion sensitivity was enhanced with the increase in ionic radius of the target ion. Titration was performed to analyze the interference of anions. To assess interferences from these ions (Cl−, NO2−, and NO3−), selectivity coefficients obtained by fixed interference method (FIM) measurements were presented. In result, the coefficients indicate that the interference can be ignored. Furthermore, characteristics of drift demonstrates that the sample exhibits long-term stability for significantly lower drift of chloride, nitrite, and nitrate ions, respectively. The Sm2O3 EIS sensor with nitrogen PIII treatment exhibits superior anion sensitivity, selectivity, and stability; therefore, this sensor is suitable for future biosensing applications.

Effects of metal doping on photoinduced hydrophilicity of SnO2 thin films

The influence of metal dopants (Mn2+, Al3+ and Cu2+) on the wetting properties of SnO2 thin films deposited by thermal evaporation is reported. The undoped and doped SnO2 films crystallize into the orthorhombic structure upon annealing at 200°C for 110 h. It is shown that wettability behaviour, before and after ultraviolet (UV) irradiation, is dependent on the ionic radius of the dopant. The contact angle of un-irradiated samples increases with increase in ionic radius of the dopant and also in comparison with the undoped sample. It is 54° for pure SnO2 and increases to 77.5°, 92.3° and 95.9° for the Al3+,Mn2+ and Cu2+ doped samples, respectively. After UV irradiation, the value is 5.4° for the undoped sample. This increases to 21.2° for Al doping reaching a minimum of 6.4° for the Mn-doped sample increasing thereafter to 63.3° for the Cu-doped sample. It is observed that pre-irradiation contact angle behaviour can be correlated with the change in roughness of the films with increasing ionic radius. In contrast, photoinduced hydrophilicity of the films correlates with their optical bandgap. The contact angle is lowest for the lowest bandgap material, i.e., Mn-doped SnO2, with a bandgap of 2.48 eV. Thus, the band structure of SnO2 that can be controlled by dopant ionic radius can in turn be employed to manipulate the wettability of these surfaces.

Vogel–Fulcher analysis of relaxor dielectrics with the tetragonal tungsten bronze structure: Ba6MNb9O30 (M = Ga, Sc, In)

In-depth analysis of the relaxor behaviour of Ba6MNb9O30 (M = Ga, Sc, In) tetragonal tungsten bronze (TTB) ceramics was carried out. Powder X-ray diffraction and scanning electron microscopy were performed in order to confirm the formation of desired phases and to determine the microstructure. Low-temperature dielectric spectroscopy was used in order to characterise the dielectric properties of these materials; the degree of relaxor behaviour was investigated in relation with the increase of ionic radius of the M cation on the B-site of the TTB structure. The dynamics of dielectric relaxation of dipoles was studied by fitting the dielectric permittivity data to the Vogel–Fulcher (VF) model in order to monitor the reproducibility and validity of the physical results. Restrictions to the VF fit were attempted besides the regular “free-fit” by constraining some of the fundamental relaxation parameters to physically sensible values. We show that VF fits are very sensitive to the fitting range resulting in a large range of fundamental parameters for the dielectric relaxation processes, and that the restriction of the frequency domain due to experimental noise or instrumentation limits has a dramatic influence on the values obtained.

INFLUENCE OF YTTRIA DOPANT ON THE STRUCTURE AND PROPERTIES of (ZrO₂)0,91−x(Sc₂O₃)0,09(Y₂O₃)х (x = 0÷0,02) crystals

We have studied the influence of the yttrium oxide (Y2O3) dopant (1 and 2 mol %) on the phase composition, structure, and electrical properties of ZrO2–9 mol % Sc2O3 solid solution. Stabilization of ZrO2 jointly with 9 mol % Sc2O3 and 2 mol % Y2O3 is shown to allow the acquisition of high phase stability transparent homogeneous crystals with a cubic structure. Their mechanical grinding is established to cause no change in the phase composition of these crystals, whereas the powders retain the initial fluorine structure. The powders preserved the original structure of the fluorite crystals. All the probed crystals reveal high microhardness and low fracture toughness. Increasing the Y2O3 concentration in the crystals led to a reduction of the maximum loads on the indenter, which the sample withstood without cracking. As is shown, the specific conductivity exhibits nonmonotonic behavior depending on the Y2O3 concentration in the crystals. Increasing the Y2O3 content to 2 mol % in the solid electrolyte reduces the conductivity of the crystals in the entire temperature range that is attributed to a decrease in the carrier mobility due to the increasing ion radius of the stabilizing ion.

Effect of RE<sup>3+</sup> Codopant on Afterglow Time of SrS:Eu<sup>2+</sup>,RE<sup>3+</sup><sup></sup>

The longest afterglow time of an orange-red- emitting SrS:Eu2+,Pr3+ afterglow phosphor by visible light irradiation was about 1010 minutes was previously achieved by varying the synthetic conditions such as amount of Li+ added, reduction temperature, reduction time, and initial Eu/Sr and Pr/Sr atomic ratios in previous paper. Therefore, this study reports on the effect of the RE3+ codopants on the afterglow time of an orange-red-emitting SrS phosphor by visible light irradiation. SrSO4:Eu3+,RE3+(RE3+ = Tm3+, Er3+, Tb3+, Nd3+, Pr3+, Ce3+, and La3+), which was the precursor for SrS phosphors, was synthesized via a liquid-phase reaction. SrSO4:Eu3+,RE3+ was pressurized at 10 MPa for a few minutes to form a compact, which was then heated under a H2S or Ar-H2 (5 mol%) reductive atmosphere at 1400 °C for 2.5 h to generate the SrS:Eu3+,RE3+ afterglow phosphor. The emission color of the SrS:Eu2+,RE3+ afterglow phosphor was orange-red and its emission peak was observed around 610 nm. The excited band of the phosphor was in the range of visible light more than 440 nm. The emission and excitation spectra of the SrS:Eu2+,RE3+ afterglow phosphor were not dependent on the RE3+ codopants. However, the afterglow time of SrS:Eu2+,RE3+ phosphor was increased with the increase of ionic radius of the coactivator. The longest afterglow time of SrS:Eu2+,Ce3+ phosphor by irradiating for 5 minutes at 1000 lx which was created from a D65 lamp was 1376 minutes. This was 9.5 times longer than that of a commercial available phosphor (CaS:Eu2+,Tm3+).

Manganese carbonate formation from amorphous and nanocrystalline precursors: Thermodynamics and geochemical relevance

The thermodynamic stabilities of different manganese carbonate phases at ambient conditions were determined by acid solution and water adsorption calorimetry. Amorphous manganese carbonate precursor provides a low energy pathway for MnCO3 crystallization analogous to that observed in (Ca-Mg-Fe)CO3 systems where crystallization enthalpies appear to be controlled by cation size (become less exothermic with increase in ionic radius). The surface energy of nanophase MnCO3 (0.64 ± 0.08 J/m2 for hydrous and 0.94 ± 0.12 J/m2 for anhydrous surface) is lower than that of nano-calcite and MnCO3 binds surface water less strongly (−65.3 ± 3 kJ/mol) than calcite (−96.26 ± 0.96 kJ/mol). This probably reflects the greater basicity of CaO compared to MnO. Substantial particle size driven shifts in the MnCO3-manganese oxide Eh-pH and oxygen fugacity-CO2 fugacity diagrams were calculated using the measured surface energies. These shifts expand the stability field of hausmannite, Mn3O4, in both aqueous and anhydrous environments. The particle size driven (caused by differences in surface energy) shifts in oxidation potential (Eh, oxygen fugacity) and pH of phase boundaries could affect stability, a electrochemical and catalytic properties and hence influence geochemical and technological processes. Manganese oxides (mainly hausmannite) dominate at the nanoscale in aerated environments, while manganese carbonate is favored in coarse-grained materials and reducing environments. In supercritical CO2, the expansion of the MnCO3 stability field leads to significant reduction of the Mn3O4 stability field.

Size of oxide vacancies in fluorite and perovskite structured oxides

An analysis of the effective radii of vacancies and the stoichiometric expansion coefficient is performed on metal oxides with fluorite and perovskite structures. Using the hard sphere model with Shannon ion radii we find that the effective radius of the oxide vacancy in fluorites increases with increasing ion radius of the host cation and that it is significantly smaller than the radius of the oxide ion in all cases, from 37 % smaller for HfO2 to 13 % smaller for ThO2. The perovskite structured LaGaO3 doped with Sr or Mg or both is analyzed in some detail. The results show that the effective radius of an oxide vacancy in doped LaGaO3 is only about 6 % smaller than the oxide ion. In spite of this the stoichiometric expansion coefficient (a kind of chemical expansion coefficient) of the similar perovskite, LaCrO3, is significantly smaller than the stoichiometric expansion coefficient of the fluorite structured CeO2. Our analysis results indicate that the smaller stoichiometric expansion coefficient of the perovskites is associated with the restraining action of the A-O sub-lattice to dimensional changes in the B-O sub-lattice and vice versa.

Hydrogen Release from Dialkylamine–Boranes Promoted by Mg and Ca Complexes: A DFT Analysis of the Reaction Mechanism

Mg and Ca β-diketiminato silylamides [HC{(Me)CN(2,6-iPr2C6H3)}2M(THF)n{N(SiMe3)2}] (M = Mg, n = 0; M = Ca, n = 1) were studied as precatalysts for the dehydrogenation/dehydrocoupling of secondary amine-boranes R2HNBH3 . By reaction with equimolar quantities of amine-boranes, the corresponding amidoborane derivatives are formed, which further react to yield dehydrogenation products such as the cyclic dimer [BH2-NMe2]2. DFT was used here to explore the mechanistic alternatives proposed on the basis of the experimental findings for both Mg and Ca amidoboranes. The influence of the steric demand of amine-boranes on the course of the reaction was examined by performing calculations on the dehydrogenation of dimethylamine-borane (DMAB), pyrrolidine-borane (PB), and diisopropylamine-borane. In spite of the analogies in the catalytic activity of Mg- and Ca-based complexes in the dehydrocoupling of amine-boranes, our theoretical analysis confirmed the experimentally observed lower reactivity of Ca complexes. Differences in catalytic activity of Mg- and Ca-based complexes were examined and rationalized. As a consequence of the increase in ionic radius on going from Mg(2+) to Ca(2+), the dehydrogenation mechanism changes and formation of a key metal hydride intermediate becomes inaccessible. Dimerization is likely to occur off-metal in solution for DMAB and PB, whereas steric hindrance of iPr2NHBH3 hampers formation of the cyclic dimer. The reported results are of particular interest because, although amine-borane dehydrogenation is now well established, mechanistic insight is still lacking for many systems.

Tandem mass spectrometric analysis of alkali metal cation–tripeptide clusters

Clusters of tripeptides bound to alkali metal cations are generated through electrospray ionization, and collision-induced dissociation tandem mass spectrometry is carried out. Fragmentation products of peptides bound to small ions are b- and y-type fragments with the ion attached, whereas fragmentation of peptides bound to larger ions leads to complete dissociation of the ion. Density functional theory calculations suggest that the ion–peptide binding energy decreases with both the increasing ion radius and the average distance between the ion and the carbonyl O atoms. There is no apparent relation between the binding energy and the partial ion charge.

Possible correlation between enthalpies of formation and redox potentials in LiMSO4OH (M = Co, Fe, Mn), Li-ion polyanionic battery cathode materials

The thermodynamic stabilities of lithium hydroxysulfates of general formula LiMSO4OH (M = Co, Fe, Mn) with layered and tavorite structures have been investigated using isothermal acid solution calorimetry. These compounds have been explored as sustainable F-free alternatives to F-based flurosulfate cathode materials. The energetic trends for layered LiMSO4OH (M = Co, Fe and Mn) samples generally showed a decrease in stability with an increase in ionic radius (Co2+ to Mn2+), reflecting weaker M–O bonds and increasing structural distortions. The low symmetry tavorite LiFeSO4OH with a structure containing corner-shared octahedral chains is less stable than layered LiFeSO4OH with a more symmetric edge-shared octahedral structure. Structural distortions within the metal octahedra as well as changes in sulfate bonding and symmetry of the SO42− groups appear to control the thermodynamic and electrochemical behavior of LiMSO4OH (M = Co, Fe and Mn) materials. Both redox potential and thermodynamic stability of layered LiMSO4OH (M = Co, Fe and Mn) can be correlated to the lowering of the sulfate bonding symmetry in the structure from C3v to C2v.

Thermodynamics of Nanoscale Calcium and Strontium Titanate Perovskites

The surface enthalpies of nanocrystalline CaTiO3 and SrTiO3 perovskites were determined using high‐temperature oxide melt solution calorimetry in conjunction with water adsorption calorimetry. The nanocrystalline samples were synthesized by a hydrothermal method and characterized using powder X‐ray diffraction, FTIR spectroscopy, and Brunauer–Emmett–Teller surface area measurements. The integral heats of water vapor adsorption on the surfaces of nanocrystalline CaTiO3 and SrTiO3 are −78.63 ± 4.71 kJ/mol and −69.97 ± 4.43 kJ/mol, respectively. The energies of the hydrous and anhydrous surfaces are 2.49 ± 0.12 J/m2 and 2.79 ± 0.13 J/m2 for CaTiO3 and 2.55 ± 0.15 J/m2 and 2.85 ± 0.15 J/m2 for SrTiO3, respectively. The stability of the perovskite compounds in this study is discussed according to the lattice energy and tolerance factor approach. The energetics of different perovskites suggest that the formation enthalpy becomes more exothermic and surface energy increases with an increase in ionic radius of the “A” site cation (Ca, Sr, and Ba), or with the tolerance factor. PbTiO3 shows a lower surface energy, weaker water binding, and a less exothermic enthalpy of formation than the alkaline‐earth perovskites.