Ba-doped Samples Research Articles

Efficiently high energy storage density in Ba2+ ion modified K0·5Na0·5NbO3 (KNN) ferroelectric ceramics for super capacitors

In the present work, Perovskites BaxK0.5-xNa0.5NbO3 (x = 0.00, 0.05, 0.10, 0.15, 0.20) were synthesized via solid-state synthesis technique. XRD analysis confirmed the successful phase formation of the synthesized perovskites. Further, Rietveld refinement revealed the presence of coexisting orthorhombic and tetragonal phases. High-resolution transmission electron microscopy (HRTEM) was employed to explore the lattice fringes and SAED patterns at nano scale level of prepared samples. The morphology was investigated using a field emission scanning electron microscope (FESEM). Dielectric measurements indicated that both the dielectric constant (ε′) and loss tangent (tan δ) exhibited significant dispersion at low frequencies and high temperatures. Notably, the Ba-doped perovskite samples demonstrated enhanced dielectric properties compared to the undoped KNN sample, with Ba0·1K0·4Na0·5NbO3 (x = 0.10) showing optimal dielectric performance, characterized by a dielectric constant (ɛ՛⁓4000) and a tanẟ ⁓7.23 at 100 Hz frequency and room temperature.AC conductivity is observed to increase with increasing both frequency and temperature. DC conductivity exhibited positive temperature coefficient indicating the semiconductor-like behavior of the prepared samples. The ferroelectric behavior was confirmed through P-E hysteresis curves and Ba0·1K0·4Na0·5NbO3 sample revealed the highest energy storage density among all prepared samples making it a suitable candidate for energy storage applications.

Enhanced thermoelectric properties in Bi2Sr2-XBaxCo2Oy ceramics by Ba doping

Bi2Sr2-xBaxCo2Oy polycrystalline samples (0.00 ≤ × ≤0.15) were prepared through the classical solid-state reaction method. It has been found that Ba-doped Bi2Sr2Co2Oy was obtained as major phase in all samples, based on XRD results. On the other hand, SEM studies have shown the presence of small amounts of secondary phases. The electrical resistivity values of all Ba doped samples decreased when compared to the undoped one, being minimum for the 0.075Ba doped ones. Seebeck coefficient increase with the increasing temperature in all samples, reaching the highest values in the 0.025 Ba doped sample. Finally, power factor has been calculated using the Seebeck coefficient and electrical resistivity values to determine the thermoelectric performances of samples. The maximum PF value of 0.14 mW/K2 m at 650 °C was obtained for 0.075Ba doped sample, which is around 25% higher than the undoped sample at the same temperature. All these results clearly show that the thermoelectric properties of the Bi2Sr2Co2Oy system can be improved by Ba doping at optimal values.

Experimental evidence of static disorder of carbonate ions in Ba-doped calcite

Incorporation of structurally incompatible Ba2+ into calcite by crystallization via amorphous calcium carbonate induces extinction of 113 reflection in X-ray diffraction patterns even at room temperature. Recently, this phenomenon has been hypothesized as deriving from the static disorder of CO32− in Ba-doped calcite, creating a marked increase in the unit-cell volume. To clarify this hypothesis by experiments, behaviors of CO32− and local structures in Ba-doped calcite samples were investigated. Powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC) indicate that CO32− ions in Ba-doped calcite are disordered, even at 91K. 13C MAS NMR spectra suggest that Ba atoms in calcite are substituted randomly for Ca atoms. The Ca K-edge X-ray absorption fine structure (XAFS) and the IR absorption spectra indicated reduction of CO32− symmetry with increasing Ba content. These local structure changes by incorporation of incompatible Ba2+ into calcite cause static disorder of CO32− at room temperature.

Effects of Ta, Nb, Ba, and Sb concentration on structural, electrical, and optical properties of SnO2 thin films prepared by metal organic decomposition using spin coating

Ta-, Nb-, Ba-, and Sb-doped SnO2 thin films were prepared by the metal organic decomposition (MOD) method using spin coating. The effects of dopant concentration on the structural, electrical, and optical properties were investigated. The growth of polycrystalline films with the tetragonal rutile structure was confirmed by X-ray diffraction and atomic force microscopy measurements. The resistivity of Ta-, Nb- and Sb-doped SnO2 samples decreased to ∼10−3 Ωcm for dopant concentrations of around 1.5–3.0 at.%. The lowest resistivities were obtained for Ta- and Sb-doped SnO2 samples. On the other hand, no decrease in resistivity was observed for Ba-doped SnO2 samples. The band gap energy of Ta-, Nb-, Ba-, and Sb-doped SnO2 samples appeared to be larger than for those prepared by other methods. It was suggested that the structural deterioration may be related to the increase in the band gap energy for MOD prepared samples in addition to the Burstein-Moss effect.

Structural phase transition, optical bandgap, interband electronic transition, and improved magnetism in bivalent Ca-, Sr-, Pb-, and Ba-doped BiFeO3 ceramics

Perovskite compounds Bi0.7A0.3FeO3−δ (BAFO) (A = Ca, Sr, Pb, and Ba) with improved optical and magnetic properties have been synthesized by solid-state method. The effect of bivalent ions substitution on the phase transition, microstructure, optical, and magnetic properties are investigated in detail. X-ray diffraction and Raman scattering spectra analyses indicate the phase transition from rhombohedral to cubic in doped samples and the coexistence of the two phases in BBFO, inducing strong lattice distortions. A blue shift observed in d–d transitions energies can reveal the decreased internal chemical pressure, thus leading to the slight increase in bandgaps of BSFO, BPFO, and BBFO. While, narrowed bandgap of 1.96 eV can be found in BCFO for the increased tailing of the conduction band edge into the gap. Besides, room-temperature ferromagnetism has been observed in Sr-, Pb-, and Ba-doped samples which can be resulted from the suppression of spiral structure of BFO. These results lay a solid foundation on further exploring the potential abilities of BFO ceramics as multiferroic photovoltaic materials.

Incorporation of Incompatible Strontium and Barium Ions into Calcite (CaCO3) through Amorphous Calcium Carbonate

Calcite is a ubiquitous mineral in nature. Heavy alkaline-earth elements with large ionic radii such as Sr2+ and Ba2+ are highly incompatible to calcite. Our previous study clarified that incompatible Sr2+ ions can be structurally incorporated into calcite through crystallization from amorphous calcium carbonate (ACC). In this study, we synthesized Sr-doped calcite with Sr/(Sr + Ca) up to 30.7 ± 0.6 mol% and Ba-doped calcite with Ba/(Ba + Ca) up to 68.6 ± 1.8 mol%. The obtained Ba-doped calcite samples with Ba concentration higher than Ca can be interpreted as Ca-containing barium carbonates with the calcite structure which have not existed so far because barium carbonate takes the aragonite structure. X-ray diffraction (XRD) patterns of the Sr-doped and Ba-doped calcite samples obtained at room temperature showed that reflection 113 gradually weakened with increasing Sr/(Sr + Ca) or Ba/(Ba + Ca) ratios. The reflection 113 disappeared at Ba/(Ba + Ca) higher than 26.8 ± 1.6 mol%. Extinction of reflection 113 was reported for pure calcite at temperatures higher than 1240 K, which was attributed to the rotational (dynamic) disorder of CO32− in calcite. Our Molecular Dynamics (MD) simulation on Ba-doped calcite clarified that the CO32− ions in Ba-doped calcites are in the static disorder at room temperature. The CO32− ions are notable tilted and displaced from the equilibrium position of pure calcite.

Tailoring perovskite surface composition to design efficient lean NOx trap Pd–La1-xAxCoO3/Al2O3-type catalysts (with A = Sr or Ba)

Here we report the influence of surface composition on the NOx removal efficiency of lean NOx trap Pd–La1-xAxCoO3/Al2O3-type catalysts. Three catalysts were prepared by the sequential impregnation of 30 wt.% of La1-xAxCoO3-type perovskites and 1.9 wt.% of Pd over alumina. The following perovskite compositions were used: La0.7Sr0.3CoO3, La0.7Ba0.3CoO3 or La0.5Ba0.5CoO3. The results of X-Ray diffraction, N2 adsorption-desorption at −196 °C, electron microscopy, temperature programmed techniques, and Raman and X-ray photoelectron spectroscopies demonstrated that lanthanum partial substitution by barium promoted the presence of Ba-based phases homogeneously distributed at the surface. This fact together with the higher basicity of Ba than Sr led to an increase of the surface basicity for Ba-doped samples. Likewise, Ba doping also favors the formation of small PdO particles homogenously distributed over the surface in close contact with the perovskite phase. Hence, the interactions between Pd and surface basic sites were also promoted. As a result, 1.9 wt.% Pd–30 wt.% La0.5Ba0.5CoO3/Al2O3 catalyst exhibited the highest NOx adsorption and reduction efficiency. Specifically, the NO global conversion and nitrogen production were as high as 90 % and 72 % at 350 °C, respectively. The enhancement of NOx storage capacity during the lean period is mainly assigned to the displacement of gas/solid equilibrium between NO2 and the available NOx adsorption sites due to the presence of higher concentration of basic sites at the surface. Meanwhile, the promotion of the NOx reduction capacity is due to the higher strength of NOx adsorbed species, which slows down the decomposition rate of NOx adsorbed species. Furthermore, the high proximity of Pd and perovskite phase favors the intermediate compounds diffusion. These results confirmed the excellent NOx removal efficiency of the 30 wt.% La0.5Ba0.5CoO3-based catalyst, even above than Pt-based model catalyst.

Doping effects on the structure and electrical properties of La2Ce2O7 proton conductors

Recent studies have reported that the conductivity of La2Ce2O7 proton conductors is improved by aliovalent doping, despite the high concentration of oxygen vacancies in the pristine material. In this study, we provide new insights into the structural and conducting properties of La2-x AxCe2O7±δ (A = Na+, Ca2+, Sr2+, Ba2+, Y3+ and W6+; x ≤ 0.2). The materials are apparently single phase compounds with a disordered fluorite-type structure by conventional X-ray diffraction; however, the local structure, studied by Raman spectroscopy, reveals a biphasic mixture of fluorite and C-type phases, which depends on dopant type and the sintering temperature. In addition, phase segregations are observed for Ca, Sr and Ba-doped samples by scanning electron microscopy. The different substitutions do not improve the bulk conduction at low temperature, and the conductivity differences between the samples are mainly ascribed to microstructural changes. High sintering temperatures produce a significant reduction of the bulk conductivity, i.e. 1.38 and 1.01 μS cm−1 at 300 °C for samples sintered at 1400 and 1500 °C, respectively. The use of Zn as sintering aid greatly improves the densification of La2Ce2O7 at lower temperature, without affecting negatively the conductivity.

Microstructural and Electrochemical Properties of Alkaline Earth Metal-Doped Li Garnet-Type Solid Electrolytes Prepared by Solid-State Sintering and Spark Plasma Sintering Methods

Li-stuffed garnet-type solid Li-ion electrolytes have been considered as a promising candidate for all-solid-state Li batteries. In this work, alkaline earth metal-doped Li garnet-type solid Li-ion electrolytes, Li6.5La2.5A0.5TaZrO12 (A = Ca, Sr, Ba) were prepared by conventional solid-state sintering (CSS) and spark plasma sintering (SPS) methods. The effect of sintering methods on the structural and electrochemical properties of the solid electrolytes was investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Among the investigated compounds, Sr-doped garnet-type Li6.5La2.5Sr0.5TaZrO12 prepared by the SPS method showed the highest Li-ion conductivity of 3.08 × 10–4 S cm–1 at 20 °C and the lowest activation energy of 0.35 eV. Both Sr- and Ba-doped samples exhibited a critical current density of 0.15 mA cm–2, and the Sr-doped Li6.5La2.5Sr0.5TaZrO12 sample showed the lowest Li-ion charge-transfer resistance of 139 Ω cm2 at room...

The Effect of Ba Doping on the Structural, Optical, Magnetic, and Dielectric Properties of BiFeO3 Nanoparticles

Nanoparticles (Nps) of Ba (0, 1 to 5 at.%)-doped BiFeO3 were synthesized by a sol-gel route at 100 °C using tartaric acid as a chelating agent. The obtained results were studied by using XRD, SEM with EDAX, TEM, UV-vis diffusion reflectance spectra, VSM, and impedance analyzer. EDAX spectra confirmed the presence of Bi, Ba, and Fe in the samples. X-ray diffraction studies showed that BiFeO3 and Bi1−xBaxFeO3 samples exhibited the expected rhombohedral perovskite structure up to a Ba concentration of 3%, whereas 4 and 5% of Ba concentration exhibited the tetragonal phase. TEM studies indicate the particle sizes in the range of 08–28 nm. Reflectance spectra measurements showed a decrease in band gap with increasing Ba concentration. Magnetic properties indicated that the undoped BiFeO3 and Ba-doped BiFeO3 samples were ferromagnetic at room temperature. The dielectric constant (e′) and loss (e″) show large dispersion behavior. The dielectric constant increases with an increase of dopant concentration, but a very high value of the dielectric constant was noticed for x = 0.05.

A Comparison Study of the Effects of Ba and La Doping in Sr2IrO4: Ir–O–Ir Bond Angle and Carrier Concentration

We perform a systematic investigation on the effects of Ba and La doping on the lattice and transport properties of Sr2IrO4, which is theoretically predicted to be a host compound of high-temperature superconductivity. We observe a drastic straightening of the Ir–O–Ir bond angle in the Ba-doped samples. The straightening of the bond angle is much weaker in the La-doped samples. It is found that the La doping leads to the introduction of electron-type charge carriers, while the charge carrier concentration does not change too much in the Ba-doped samples. As a result, both the resistivity and the magnetic moments decrease much faster in the La-doped samples, compared to those in the Ba-doped samples. The present results suggest that it is the charge carrier density rather than the Ir–O–Ir bond angle that dominates the magnetic and transport properties of the Sr2IrO4 system.

Comparison of benzene and toluene photodegradation under visible light irradiation by Ba-doped BiFeO3 magnetic nanoparticles with fast sonochemical synthesis.

Bi1-xBaxFeO3 (x = 0.02, 0.04 and 0.07) multiferroic materials with a diameter in the range of 30-40 nm were controllably synthesized by a facile ultrasonic method, with a very short reaction time of 5 min at a low temperature of 30 °C, and the resulting BiFeO3 magnetic nanoparticles (BFO MNPs) exhibited enhanced magnetic and photocatalytic performance. The substitution of Ba2+ ions for Bi3+ ions at the A-site of BFO MNPs, even at only 2%, decreased their particle size and distorted the lattice in the rhombohedral structure of BFO MNPs. Increasing the Ba doping to 7% greatly increased the ferromagnetic properties of BFO MNPs from 3.55 to 6.09 emu g-1. In comparison with pure BFO MNPs, 7% Ba substitution in the Ba-doped BFO MNP samples produced strong absorption in the visible light region, decreasing the band-gap energy from 2.11 to 1.86 eV. Photoluminescence (PL) spectroscopy identified the band-gap emission for BFO MNPs at 587 nm, while for both pure and Ba-doped samples, the other emissions were attributed to the defect states related to oxygen deficiencies inside the band gap. After 50 min of visible light irradiation, Bi1-xBaxFeO3 (x = 7%), with the lowest band gap energy, highest magnetization and smallest particle size, showed almost complete photocatalytic degradation of toluene and benzene (100 mg L-1), with 91 and 81% reduction, respectively, in total organic carbon (TOC). For all irradiation times, the mineralization efficiency of toluene was higher than that of benzene, which demonstrated that toluene is more sensitive to photocatalytic oxidation than is benzene.

Effect of barium doping on the physical properties of zinc oxide nanoparticles elaborated via sonochemical synthesis method

The aim of this work is to study the effect of barium (Ba) doping on the optical, morphological and structural properties of ZnO nanoparticles. Undoped and Ba-doped ZnO have been successfully synthesized via sonochemical method using zinc nitrate, hexamethylenetetramine (HMT) and barium chloride as starting materials. The structural characterization by XRD and FTIR shows that ZnO nanoparticles are polycrystalline with a standard hexagonal ZnO wurtzite crystal structure. Decrease in lattice parameters from diffraction data shows the presence of Ba2+ in the ZnO crystal lattice. The morphology of the ZnO nanoparticles has been determined by scanning electron microscopy (SEM). Incorporation of Ba was confirmed from the elemental analysis using EDX. Optical analysis depicted that all samples exhibit an average optical transparency over 80%, in the visible range. Room-temperature photoluminescence (PL) spectra detected a strong ultraviolet emission at 330 nm and two weak emission bands were observed near 417 and 560 nm. Raman spectroscopy analysis of Ba-doped samples reveals the successful doping of Ba ions in the host ZnO.

Effect of Ba–Nb co-doping on the structural, dielectric, magnetic and ferroelectric properties of BiFeO3 nanoparticles

Multiferroic BFO nanoparticles of compositions Bi1−xBaxFeO3 and Bi1−xBaxFe1−xNbxO3 (x=.05 and .1) have been synthesized using sol–gel followed by an auto-combustion route. The effect of Ba–Nb co-doping on structural, magnetic, dielectric, leakage current and ferroelectric properties has been investigated. XRD patterns confirm the rhombohedral phase for all the samples in which traces of pseudo-cubic phase have been observed as a result of co-doping. The residual and saturation magnetization get increased significantly, which is attributed to a decreased degree of structural distortion and smaller particle size due to co-doping. Dielectric studies show strong dispersion for Ba-doped samples while Ba–Nb co-doped samples are nearly frequency independent. Furthermore, dielectric constant (ε∞) at higher frequencies increases with doping level whereas dielectric loss decreases due to reduction in defect centers by co-doping. Temperature dependent dielectric analysis reveals strong anomaly near magnetic transition (TN), signifying magnetoelectric coupling for all the samples. Leakage current has been decreased to 2–3 orders of magnitude and conductivity behavior has come close to ohmic type for 10% Ba–Nb co-doped sample, which suggested a significant reduction in oxygen vacancies. The saturation level of ferroelectric loop is also improved with doping level and remnant polarization increases from 1.28μC/cm2 for 5% Ba-doped to 3.24μC/cm2 for 10% Ba–Nb co-doped sample. Hence, Ba and Nb co-doped BFO nanoparticles can be used as a promising candidate for magneto-electric applications.

Dielectric Relaxation Measurements in La<sub>1.94</sub>Ba<sub>0.06</sub>Mo<sub>2</sub><sub>-</sub><sub>y</sub>W<sub>y</sub>O<sub>9</sub><sub>-</sub><sub>δ</sub> (y=0, 1.0) Oxide-Ion Conductors

The influence of barium doping on the oxygen-ion diffusion and phase transition in the La2Mo2-yWyO9-δ (y=0, 1.0) oxide-ion conductors has been systematically investigated via dielectric techniques. In the Ba-doped La2Mo2O9 samples there are only two dielectric relaxation peaks Pd1 and Pd2, which are associated with the short-distance diffusion of oxygen vacancies. But in the Ba-doped La2MoWO9 members, three peaks are detected, including peak Pd1, Pd2, and peak Ph. The last is associated with the phase transition process from the static disordered state to the dynamic disordered state of oxygen ion/vacancy distribution.

Structural and Dielectrical Properties of Ag- and Ba-Substituted Hydroxyapatites

Ag- and Ba-doped hydroxyapatite (HAp) samples were synthesized by sol–gel method. The crystallite sizes for all the samples were found to vary from 26 to 39 nm. Neither Ag nor Ba did result in dramatic changes in the morphology of all the samples, and the Ca/P molar ratio was varied. The dielectric parameters of the samples were changed with the dopant content. The maximum and minimum values of the dielectric constant were observed for 2.0 %Ba-HAp and 0.5 %Ba-HAp samples. The alternating current conductivity indicates that all the samples exhibit the insulator behavior. The results of the biological tests revealed that Ag-containing samples have an antimicrobial activity, while no antimicrobial activity was detected for both HAp and Ba-doped HAp samples.

Investigation of transport behavior in Ba doped BiFeO3

Bi1−xBaxFeO3 (x=0.00–0.25) samples were prepared by conventional solid state reaction method. X-ray diffraction revealed the rhombohedrally distorted perovskite structure for undoped BiFeO3 with a phase transition from rhombohedral to pseudo cubic on Ba substitution. The leakage current density of 10% Ba substituted sample is found to be four orders of magnitude less than that of the pure BiFeO3. Grain boundary limited conduction and space charge limited conduction mechanisms are involved in low and high electric field regions respectively for all the samples except 10% Ba doped BFeO3 which obeys grain boundary limited conduction mechanism in whole of the electric field range. Dielectric measurements showed that the dielectric constant and dielectric loss attained their minimum values at 10% Ba substitution. Thus 10% Ba is found to be optimum concentration to have better multiferroic properties. Undoped BiFeO3 and 5% Ba doped samples have very large values of dielectric constants and leakage current densities which can be attributed to a large number of oxygen vacancies in these samples, indicating an extrinsic response of these compositions.

Magnetic and electrical transport properties of La 0.5A 0.5CoO 3 nanoparticles (A = Sr, Ca, and Ba)

We have investigated the effect of particle size on the electrical transport and magnetic properties of La 0.5A 0.5CoO 3 (A = Sr, Ca, and Ba) nanoparticles synthesized by sol–gel technique. A size-induced metal to insulator transition is observed in the resistivity behaviour of Sr- and Ba-doped samples as the dimension changes from higher to lower ones. The magnetoresistance exhibits almost linear behaviour throughout the studied field range. The zero-field-cooled (ZFC) and field-cooled (FC) magnetizations display a broad paramagnetic to ferromagnetic transition at T C with a large magnetic irreversibility. The magnetization results indicate that Co 3+ ions are in the intermediate spin state but Co 4+ ions stay in a mixture of intermediate and high spin states. The observed frequency dependent shoulder in the in-phase and the peak in the out of phase component of the ac susceptibility indicate the glassy nature of the samples. The analysis of the ac magnetization results suggests that the magnetic behaviour is consistent with the cluster glass model.

Synthesis and Superconductivity in Ba-doped (Ru,Cu)(Sr,Nd)2(Nd,Ce)2Cu2O z Compounds

We prepared various (Ru0.5Cu0.5)(Sr1.67−xBaxNd0.33)(Nd1.34Ce0.66)Cu2Oz samples with varying Ba contents by x=0, 0.1, 0.2, 0.33, 0.5 and 0.835. X-ray diffraction revealed that the phase purity of the samples increases as the Ba-doping content increases and single- phase compounds could be obtained for samples with 0.1≤x≤0.33. Contrary to the Ba-free sample, superconductivity could be induced by partially substituting Ba for Sr and superconductivity with onset Tc of about 15 K is observed for the sample with x=0.2. The superconducting behavior of the Ba-doped samples is discussed in conjunction with thermoelectric power measurements.

Symmetry rules and strain/order-parameter relationships for coupling between octahedral tilting and cooperative Jahn–Teller transitions in ABX 3 perovskites. II. Application

The structural evolution of selected perovskites containing Jahn-Teller cations has been investigated in the light of a formal analysis of symmetry hierarchies for phase transitions driven by octahedral tilting and Jahn-Teller cooperative distortions. General expressions derived from the strain/order-parameter coupling relationships allowed by symmetry are combined with observed changes in lattice parameters to reveal details of order-parameter evolution and coupling. LuVO3, YbVO3, YVO3 and CeVO3 are representative of systems which develop Jahn-Teller ordering schemes associated with irreducible representations M2+ and R3+ of the space group Pm3m. Tilting of their octahedra is associated with M3+ and R4+. The Pnma (M3+ + R4+ tilting) <--> P2(1)/a (M3+ + R4+ tilting, R3+ Jahn-Teller order) transition below room temperature is close to second order in character. Shear strains which depend primarily on tilt angles show little variation, implying that there is only weak coupling between the tilting and Jahn-Teller order parameters. The subsequent P2(1)/a <--> Pnma (M3+ + R4+ tilting, M2+ Jahn-Teller order) is first order in character, and involves either a reduction in the R4+ tilt angle or a change in the strength of tilt/Jahn-Teller order-parameter coupling. In LaMnO3, the isosymmetric Pnma (M3+ + R4+ tilting) <--> Pnma (M3+ + R4+ tilting, M2+ Jahn-Teller order) transition can be described in terms of a classical first-order transition conforming to a 246 Landau expansion with negative fourth-order coefficients. Strain evolution in Ba-doped samples suggests that the transition becomes second order in character and reveals a new strain relaxation mechanism in LaMnO3 which might be understood in terms of local strain heterogeneities due to the disordering of distorted MnO6 octahedra. Transitions in PrAlO3 and La(0.5)Ba(0.5)CoO3 illustrate the transformation behaviour of systems in which the Jahn-Teller ordering scheme is associated with the irreducible representation Gamma3+. Overall, coupled tilting + Jahn-Teller phase transitions in perovskites conform to mean-field behaviour, consistent with the underlying role of strain in promoting long interaction lengths.