Oxide perovskites designed by configurational entropy

  • Acronym: EntroPer
  • Project Code: PN-III-P1-1.1-PD-2021-0625
  • Contract Number: 22PD
  • Start: 01/04/2022
    End:  31/03/2024
  • Duration: 24 months
  • Budget: 249.996,00 Lei
  • Contracting Agency:: Executive Agency for Higher Education, Research, Development and Innovation Funding

  • Coordinating Institution: : University POLITEHNICA of Bucharest – National Research Center for Micro and Nanomaterials

    Address: Spl. Independentei 313, Sector 6, Bucharest, Romania
    Phone: +4021.402.9465

Project manager: Lect. Dr. Eng. Vasile-Adrian SURDU

Supervisor: Prof. Dr. Eng. Adelina Carmen IANCULESCU

The concrete objective of the project is to contribute to the fundamental understanding of the role of long-order and short-order interactions in the phenomenology of relaxor-ferroelectric behavior. This will be realized by inducing chemical disorder in oxide systems, by entropy-driven stabilization on A and/or B-site of ABO3 perovskite structure.  The main objective is ambitious considering the complexity of the proposed compositions with 5 cations on an equivalent crystallographic site of ABO3 perovskite structure, and potential difficulties in preparing single-phase ceramics. The approach of the project is experimental and multidisciplinary and involves activities of powders preparation by wet-chemistry Pechini method, elaboration of ceramics by alternative sintering strategies (conventional sintering and Spark Plasma Sintering) and complex investigation of the composition, structure, microstructure as well as functional properties (relative permittivity, dielectric losses). The successful achievement of the objective may open a way to new design strategy and understanding of the chemical disorder influence and microstructural design on electrical behavior for perovskite oxide relaxors.

The estimated scientific results of the project are summarized in two points:
(i) Understanding of the chemical disorder contribution to functional properties of and domain wall formation in relaxors with high configurational entropy on A-site, B-site or both cationic sites of the perovskite structure. Result indicators such as permittivity, dielectric constant, dielectric loss values, ferroelectric domain walls characteristics will be assessed to relative to typical perovskite relaxors.
(ii) Understanding of the composition – structure – microstructure – functional properties relation in high entropy perovskites. The results indicators are the distortion of the perovskite structure for high entropy oxides, grain size, grain boundary density assessed relative to permittivity, dielectric constant and dielectric loss values.

Scientific results and dissemination

 

Phase 1

 

Research activities were carried out for the synthesis of powders of nominal composition (Bi0.2K0.2Ba0.2Sr0.2Ca0.2)TiO3 by wet chemical methods. The composition, thermal stability and morphology of the obtained nanoparticles were investigated. It was found that processing at temperatures between 900 and 1000°C leads to obtaining the desired composition, in a mixture of polymorphic phases specific to the perovskite-type structure and with particle sizes of approximately 10-16 nm. The consolidation of the powder carried out by alternative methods allowed the consolidation of ceramic materials with an average granular size in the range of 17-50 nm depending on the sintering route and the processing temperature and with a uniform distribution of chemical elements in the case of ceramics processed by conventional sintering. The dielectric behaviour of the obtained ceramic materials suggests a relaxor-type behaviour, with a permittivity maximum at temperatures dependent on the frequency and the granular size of the studied ceramics.

The dissemination of the results was achieved by participating with an oral presentation entitled “High entropy perovskites oxides: synthesis and characterization”, authors Vasile-Adrian Surdu, Mariana Andreea Marinică, Ovidiu Oprea, Adelina Carmen Ianculescu at the “22nd Romanian International Conference on Chemistry and Chemical Engineering”, September 7-9, 2022, which took place in Sinaia, Romania.

 

Phase 2

 

Research activities were carried out for the synthesis of powders of nominal composition Ba(Ti0.2Sn0.2Hf0.2Zr0.2Ce0.2)O3 and (Bi0.2K0.2Ba0.2Sr0.2Ca0.2)(Ti0.2Sn0.2Hf0.2Zr0.2Ce0.2)O3 by wet chemical methods. The composition, thermal stability and morphology of the obtained nanoparticles were investigated. Thermal processing conditions were determined to obtain the perovskite phase of interest in an optimal proportion for each of the compositions. Powder consolidation carried out by alternative methods allowed the consolidation of ceramic materials with controllable average granular size depending on the sintering route and the processing temperature and with a uniform distribution of chemical elements. For the ceramic materials of nominal composition Ba(Ti0.2Sn0.2Hf0.2Zr0.2Ce0.2)O3 the dielectric behavior was investigated and was correlated with the microstructure of the investigated materials.

The dissemination of the results was achieved by publishing the article Surdu, V.-A.; Marinică, M.-A.; Patru, R.-E.; Oprea, O.-C.; Nicoara, A.I.; Vasile, B.Ș.; Trușca, R.; Ianculescu, A.-C. High-Entropy Lead-Free Perovskite Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 Powders and Related Ceramics: Synthesis, Processing, and Electrical Properties. Nanomaterials 2023, 13, 2974. https://doi.org/10.3390/nano13222974 and by participating in an oral presentation entitled “High entropy perovskite ceramics prepared by alternative routes”, authors Surdu Vasile-Adrian, Nicoară Adrian Ionuț, Pătru Roxana Elena , Trușca Roxana, Oprea Ovidiu, Ianculescu Adelina Carmen at the “The XVIIIth Conference of the European Ceramic Society”, July 2-6, 2023, which took place in Lyon, France.

 

Phase 3

 

Research activities were carried out for the characterization of powders and ceramic materials of nominal composition (Bi0.2K0.2Ba0.2Sr0.2Ca0.2)(Ti0.2Sn0.2Hf0.2Zr0.2Ce0.2)O3. The structure, particle morphology and chemical homogeneity of the powders were investigated. Powder consolidation carried out by alternative methods allowed the obtaining of ceramic materials with controlled grain size, depending on the processing route and conditions and with an uniform distribution of chemical elements. The dielectric behavior was investigated and correlated with the microstructure of the investigated materials.

The dissemination of the results was achieved by participating with an oral presentation entitled “High entropy lead-free perovskite powders and related ceramics”, authors Vasile-Adrian Surdu, Mariana-Andreea Marinică, Roxana-Elena Pătru, Ovidiu Oprea, Adrian Ionuț Nicoară, Bogdan Ștefan Vasile, Roxana Doina Trușcă, Adelina Carmen Ianculescu at the conference “13TH INTERNATIONAL CONFERENCE ON MATERIALS SCIENCE & ENGINEERING”, March 13-16, 2024, which took place in Brașov, Romania.

Article:

  1. Surdu, V.-A.; Marinică, M.-A.; Patru, R.-E.; Oprea, O.-C.; Nicoara, A.I.; Vasile, B.Ș.; Trușca, R.; Ianculescu, A.-C. High-Entropy Lead-Free Perovskite Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 Powders and Related Ceramics: Synthesis, Processing, and Electrical Properties. Nanomaterials 2023, 13, 2974. https://doi.org/10.3390/nano13222974

Conference:

  1. “High entropy perovskite ceramics prepared by alternative routes”, authors Surdu Vasile-Adrian, Nicoară Adrian Ionuț, Pătru Roxana Elena , Trușca Roxana, Oprea Ovidiu, Ianculescu Adelina Carmen at the “The XVIIIth Conference of the European Ceramic Society”, July 2-6, 2023, which took place in Lyon, France.
  2. “High entropy perovskites oxides: synthesis and characterization”, authors Vasile-Adrian Surdu, Mariana Andreea Marinică, Ovidiu Oprea, Adelina Carmen Ianculescu at the “22nd Romanian International Conference on Chemistry and Chemical Engineering”, September 7-9, 2022, which took place in Sinaia, Romania.
  3. “High entropy lead-free perovskite powders and related ceramics”, authors Vasile-Adrian Surdu, Mariana-Andreea Marinică, Roxana-Elena Pătru, Ovidiu Oprea, Adrian Ionuț Nicoară, Bogdan Ștefan Vasile, Roxana Doina Trușcă, Adelina Carmen Ianculescu at the conference “13TH INTERNATIONAL CONFERENCE ON MATERIALS SCIENCE & ENGINEERING”, March 13-16, 2024, which took place in Brașov, Romania.
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