Accelerated design and discovery of perovskites with high conductivity for energy applications through machine learning

We use machine learning tools for the design and discovery of ABO3-type perovskite oxides for various energy applications, using over 7000 data points from the literature. We demonstrate a robust learning framework for efficient and accurate prediction of total conductivity of perovskites and their classification based on the type of charge carrier at different conditions of temperature and environment. After evaluating a set of >100 features, we identify average ionic radius, minimum electronegativity, minimum atomic mass, minimum formation energy of oxides for all B-site, and B-site dopant ions of the perovskite as the crucial and relevant predictors for determining conductivity and the type of charge carriers. The models are validated by predicting the conductivity of compounds absent in the training set. We screen 1793 undoped and 95,832 A-site and B-site doped perovskites to report the perovskites with high conductivities, which can be used for different energy applications, depending on the type of the charge carriers.

Effect of Average Ionic Radius of A-site, B-site in Ba0.85X0.15TiO3, BaY0.15Ti 0.85O3 Systems Respectively (X = Pb, Ca, Co), (Y = Zr, Mn, Si) as a Perovskite Structure Ceramics (ABO3) on Crystal Structure, Curie Temperature

Barium titanate BaTiO3 is one of the most ferroelectrics. Its commonly used in capacitors due to its high dielectric constant. In this study, our goal is to determine the extent to which the change in the average ionic radius of A, B sites affects the structural, dielectric properties of this ceramic. In this study, barium titanate (Ba0.85X0.15TiO3, BaY0.15Ti0.85O3) (X = Pb, Ca, Co, Y= Zr, Si, Mn) was prepared by solid state reaction method in which the calcination temperature was 1200 °C for 2 hours. Structural characterization and dielectric properties were determined and calculated by using x-ray diffractometer, RCL-Meter (PM6303) at frequency 20 Hz using different temperature respectively. The results of the work showed that the average ionic radius at the A, B sites plays a large and clear role in determining the values of the dielectric constant and Curie temperature in perovskites in addition to the structural parameters.

A Combinatory Ferroelectric Compound Bridging Simple ABO3 and A-site-Ordered Qudruple Perovskite

The simple ABO3 and A-site-ordered AA′3B4O12 perovskites represent two types of the most classical perovskite-based functional materials. While there are well-known simple perovskites with ferroelectric properties, so far there is no report of ferrolectricity due to symmetry breaking transition in A-site-ordered quadruple perovskites, AA′3B4O12. Here we report the synthesis at high pressure and temperature of a new A-site-ordered perovskite, PbHg3Ti4O12. Remarkably, PbHg3Ti4O12 is the only known quadruple perovskite that transforms from a high-temperature centrosymmetric (Im-3), paraelectric phase to a low-temperature, non-centrosymmetric (Imm2) ferroelectric phase. Moreover, the average ionic radius of A-site cations for PbHg3Ti4O12 is large~ 1.1 Å and the tolerance factor t is about 0.88. Surprisingly the coordination chemistry of Hg2+ is changed from the usual square planar as in typical A-site-ordered quadruple perovskite to a rare stereo type with 8 ligands in PbHg3Ti4O12 driven via pressures. Thus PbHg3Ti4O12 appears to be a combinatory link from simple ATiO3 perovskite to AA′3B4O12 type A-site-ordered perovskites, sharing both displacive ferroelectricity with the former and the structure coordination with the latter. This is the first example of ferroelectricity due to a symmetry breaking phase transition in AA′3B4O12-type A-site-ordered perovskite, and opens a new direction to search for ferroelectric materials in combinatory perovskites.

EFFECT OF MEAN ION SIZE AND SPATIAL SPIN DISORDERS FOR (La1-xYx)2/3Ca1/3MnO3 MANGANITES

The structure and transport properties of perovskite ( La 1-x Y x)2/3 Ca 1/3 MnO 3 (0≤x≤0.3) systems are systematically investigated. It is found that all the specimens show a single-phase structure and reveal a direct relationship between the Curie temperature Tc and the average ionic radius <rA> of La site. With increasing Y 3+ doped content, the metal-insulator transition temperature T MI (M-I) shifts to lower temperature. While the relevant resistivity peak ρp is sharp increased, for the specimens with large doping content, x=0.3, it has enhanced eight orders of magnitudes larger than the non-doped samples (x=0.0). At high concentration area, that is to say, when x>0.1, magnetic studies show a gradual increase of antiferromagnetic interaction with an increase of x, ultimately leading to a spatial-spin disorders, that is, spin-glass-like state for x=0.2 and x=0.3 compounds at about 35 K. The results show that it has connected a reduction of Tc and an increase in magnetoresistance with a decrease in the microstructural Mn - O - Mn bond angle.

Structural derivation and crystal chemistry of apatites

The crystal structures of the [A(1)2][A(2)3](BO4)3 X apatites and the related compounds [A(1)2][A(2)3](BO5)3 X and [A(1)2][A(2)3](BO3)3 X are collated and reviewed. The structural aristotype for this family is Mn5Si3 (D88 type, P63/mcm symmetry), whose cation array approximates that of all derivatives and from which related structures arise through the systematic insertion of anions into tetrahedral, triangular or linear interstices. The construction of a hierarchy of space-groups leads to three apatite families whose high-symmetry members are P63/m, Cmcm and P63 cm. Alternatively, systematic crystallographic changes in apatite solid-solution series may be practically described as deviations from regular anion nets, with particular focus on the O(1)—A(1)—O(2) twist angle φ projected on (001) of the A(1)O6 metaprism. For apatites that contain the same A cation, it is shown that φ decreases linearly as a function of increasing average ionic radius of the formula unit. Large deviations from this simple relationship may indicate departures from P63/m symmetry or cation ordering. The inclusion of A(1)O6 metaprisms in structure drawings is useful for comparing apatites and condensed-apatites such as Sr5(BO3)3Br. The most common symmetry for the 74 chemically distinct [A(1)2][A(2)3](BO4)3 X apatites that were surveyed was P63/m (57%), with progressively more complex chemistries adopting P63 (21%), P\bar 3 (9%), P\bar 6 (4.3%), P21/m (4.3%) and P21 (4.3%). In chemically complex apatites, charge balance is usually maintained through charge-coupled cation substitutions, or through appropriate mixing of monovalent and divalent X anions or X-site vacancies. More rarely, charge compensation is achieved through insertion/removal of oxygen to produce BO5 square pyramidal units (as in ReO5) or BO3 triangular coordination (as in AsO3). Polysomatism arises through the ordered filling of [001] BO4 tetrahedral strings to generate the apatite–nasonite family of structures.

Synthesis and Na+ conduction properties of the ceramics of Na5YSi4O12-type phosphate-substituted solid solutions

The Na+-superionic conducting ceramics with Na5YSi4O12-type structure were synthesized using the composition formula of Na3+3x−yY1-xPySi3-yO9, in which some portions of Na+ ions are considered to replace Y3+as Na(13+8x−4y/3) [Na(4x−1)/3Y(4–4x)/3] [P4y/3Si(12–4y)/3]O12 according to Na5YSi4O12-type composition formula. The average ionic radius of the 6-coordinated Y3+ sites [= (4x − 1)/ 3 ×rNa + (4 - 4x)/3 × rY] approximately covered the range of rGd and to rSm. The ionic conduction properties were strongly dependent upon the combination of composition parameters, x and y. In this report, the dependence of conduction properties on the composition is discussed on the basis of structural considerations.