Gradual Evolution Research Articles

A Cooperation–Competition Evolutionary Dynamic Model Over Signed Networks

Signed networks are widely applied to describe cooperative and competitive interaction relationships arising from various social, biological and physical systems. In this paper, a cooperation-competition evolutionary dynamic model is offered to explain the gradual evolution of the interaction relationship between neighboring nodes in signed networks. The core feature of our model is to portray the interaction relationship between neighboring nodes as a nonlinear function of the state difference, i.e., neighboring nodes cooperate with each other only if their state difference is within a limited range (called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cooperation range</i> ); otherwise they antagonize with each other. We investigate the leader-follower dynamics, and present the lower bound of the convergence rate by using the infinite norm of products of sub-stochastic matrices. For the leaderless dynamics, we establish algebraic conditions with respect to the state differences and the cooperation range for realizing consensus and polarization behaviors. Finally, numerical examples are provided to illustrate the evolution dynamics.

SELF-CONCEPT development of school-aged children with congenital upper limb differences: A mixed-methods study

BackgroundSchool-aged children enter an essential phase of psychosocial development in which they begin to form their self-concept. Having a negative self-concept has a direct relationship on the gradual evolution of a child's personality which can influence academic and career success, peer interactions and relationships, generativity and life satisfaction and meaning. There is limited research examining self-concept in children with congenital upper limb differences. ObjectivesDescribe self-concept in school-aged children with congenital upper limb differences (CULD). MethodsIn this convergent mixed methods study, we used the Piers Harris Children's Self-Concept Scale (PHCSCS) and modified photovoice methodology to explore self-concept in school aged children with CULD. The quantitative results from the PHCSCS were merged with the qualitative findings from the 63 photographs and 63 written descriptions provided by nine children. ResultsMean self-concept was 51.22 (±10.43). Mean domain scores: behavioral adjustment 52 (±8.19), freedom from anxiety 48.56 (±10.42), happiness and satisfaction 49.44 (±10.73), intellectual and school status 54.78 (±10.31), and social acceptance 49.89 (±8.64). Nine participants described five themes of self-concept: emotions, sense of accomplishments, positive view of oneself and one's physical body, hobbies, and a sense of connection. Children defined their self-concept through expressions of self-efficacy, self-image, and social identity. ImplicationsResults created a more comprehensive description of self-concept, and expanded understanding of the social identity of school-aged children with congenital upper limb difference. Future research is needed to examine the relationships between self-efficacy, self-image, and social identity to develop interventions promoting healthy self-concept development.

Microstructural evolution and mechanical property of friction stir welded joints in AlSi10Mg alloys fabricated by laser powder bed fusion

Friction stir welding (FSW) was introduced to join laser powder bed fusion (LPBF) AlSi10Mg alloys in this study. Microstructure and texture evolution, microhardness distribution and tensile properties of the FSW joints were investigated. The evolution of grain size, grain boundary and misorientation angles distribution, dynamic recrystallization and crystallographic texture in various regions of the FSW joint concerning base metal (BM), thermo-mechanically affected zone (TMAZ), upper part of nugget zone (UPNZ) and low part of nugget zone (LPNZ) was characterized by using electron back-scattered diffraction (EBSD). The analysis reveals a strong texture evolution of shear components on the TMAZ, UPNZ and LPNZ as well as a fully recrystallized grain structure on the UPNZ and LPNZ. Additionally, a gradual evolution in Si-rich eutectic from continuous cellular networks in the BM to totally globularized particles in the UPNZ and LPNZ occurs in the FSW joint. The microhardness rapidly decreases to the TMAZ from the BM through heat affected zone (HAZ) reaching the lowest value of ∼65.0 HV at the TMAZ/NZ boundary. The FSW joint in LPBF AlSi10Mg alloys exhibits an ultimate tensile strength (UTS) of 247 MPa and an elongation-to-failure (EI) of 8.8%. The UTS of FSW joints is reduced compared to the BM, but the EI has been increased by 160%, implying an improvement in tensile ductility.

Tantalum Oxide Thin Films Sputter-Deposited by Oxygen Gas Pulsing

Tantalum oxide thin films are deposited by DC reactive magnetron sputtering from a tantalum metallic target and argon + oxygen. The oxygen gas is pulsed during the deposition with a constant pulsing period T = 10 s, whereas the introduction time of the reactive gas, namely the tON injection time, is systematically changed from 0 to 100% of T. Therefore, composition of as-deposited TaOx films is continuously changed from pure metallic tantalum to the over-stoichiometric Ta2O5 material. Films adopt the body-centered cubic structure (metallic Ta) for the lowest tON injection time values (oxygen stoichiometry x &lt; 1.0) and become amorphous for the longest ones. It is shown that the tON injection time is a key parameter to deposit either homogeneous tantalum oxides, or periodic Ta/TaOx multilayers with alternations close to 3 nm. Optical transmittance in the visible region of the film/glass substrate system and electrical conductivity vs. temperature both exhibit a gradual evolution from metallic (σ300K = 8.17 × 105 S m−1 with an opaque behavior) to semiconducting (σ300K = 1.97 × 103 S m−1 with a semi-transparent transmittance) and finally to dielectric properties (σ300K &lt; 10−5 S m−1 for interferential films) as a function of the oxygen concentration in the films.

Del's Growth: A Typical Example of Construction of Female Self-consciousness—A Postmodern Feminist Analysis of Lives of Girls and Women

Alice Munro is a famous contemporary Canadian women writer and the winner of 2013 Nobel Prize in literature. She is known as the ""master of contemporary short stories"". Munro is very concerned about the life experience of ordinary women. She always focuses on the daily trifles and details of ordinary women and describes their journey from a girl to a wife in detail, especially focusing on the psychological fluctuations and twists and turns of women. They seem fragile, but they are persistent. Munro's works are full of postmodern feminism, focusing on women's self-awareness and subjective conscious construction.&#x0D; From the perspective of postmodern feminism, the thesis focuses on the gradual formation and evolution of the heroine's self-consciousness in Alice Munro's only ""full-length"" novel Lives of Girls and Women in the process of growing up from a girl to a woman, and how female images to jump out of the hierarchy, logical structure and linear narrative surrounded by men's words and begin to express own world.&#x0D; The introduction gives an overview of Alice Munro and the novel Lives of Girls and Women, literary reviews at home and abroad, some key elements in postmodern feminism, and the significance of this thesis.&#x0D; The body section consists of three chapters: Chapter One focuses on ""Del observes the adult life"". Through Del's observation, the life of Uncle Benny's wife, two aunts, her mother and the teacher unfolded. Chapter Two analyzes ""Self-consciousness of Del begins to construct"". Del gradually began to grow up. The awakening of sexual consciousness, the doubt of belief and the excavation of herself have gradually become the theme of this adolescent girl's life. Chapter Three revolves around ""Establishment and Perfection of her self-consciousness"". Finally, she got rid of her fantasy and self-deception, her past mistakes and perplexity, and left home to start her real life.&#x0D; The conclusion part summarizes that from the perspective of postmodern feminism, the self-growth and consciousness awakening of Del is how women break away from the role of ""good women"" who meet the social expectations and find their own real nature. Munro challenges the forces we take for granted and shakes the foundations of our lives. Women perceive the world in a way different from men and resist the grandeur of history with daily trivialities. Munro constructs women's value expresses her voice and embodies her choice of will by transcending feminism and returning to women's ontological experience.

Meaning and Replicability of Social Psychological Experiments: A Personal Account

In this paper I describe the gradual evolution of experimental social psychology from a so called “science of discovery”, with invariant findings over time and space, to an art of theatrical reflection with self-made reproductions of social life to so engage in more thoughtful action. I do this by means of a narrative account of my sixty year long personal experience with the various changes in the discipline, from the many cases of non-replicability early in my career, to the splendid discovery by vigilant students at my department of the probably most impressive case of fraud in the history of the social sciences, to the persistent denial of a need for a new logic by orthodox positivists in the discipline, even after more than half of the carefully designed replications of important experiments in the discipline failed. I look at this evolution through the lens of gradual objectification in science as a whole, from the most distant objects, such as stars, to the closer and closer reality of our own existence, namely the production and processing of meaning, and the inevitable recursivity (historicity) and incompleteness (one cannot include one’s own discourse in the discourse one has at that moment) of that endeavour. I also describe moments of institutional evolution, its political besides scientific interest, and encounters with the most influential protagonists in the development of the new logic. I also reflect a moment on the theoretical and methodological implications of that new logic, and end with showing how the theme of social engagement and the move toward cultivated action, rather than by freezing history in the so called truth of invariance, was actually the core idea in the work of Kurt Lewin, and has been used inadvertently in the subsequent use of experiments in the discipline, even by those who pretended to be the astronomers of the mind. But with the clear note that reflection on social life in the form of self-made reproductions of that life, is probably the most human thing we can do, and enables us to create culture, rather than blind evolution in merely physical or biological terms. So, making experimental social psychology a valuable tool of humanization as well, but only when properly used.

Lennox–Gastaut Syndrome: Challenges in Diagnosis – Interviews with Two Key Opinion Leaders

Lennox–Gastaut syndrome (LGS) is a severe childhood-onset epilepsy syndrome that can be challenging to identify due to its heterogeneous and evolving presentation. During interviews conducted by EMJ in July and August 2023, Karen Keough, a child neurologist specialising in paediatric refractory epilepsy at Texas A&amp;M University School of Medicine, Round Rock, USA, and Rhys Thomas, an adult neurologist specialising in epilepsy (leading on learning disability and genetic testing) at the Royal Victoria Infirmary, Newcastle, UK, and Newcastle University, UK, gave their informed opinions on the challenges of diagnosing LGS. The experts spoke about the characteristic features of LGS, and how its gradual evolution from childhood onset can impede diagnosis. In particular, the issues around diagnosing LGS in adulthood, after considerable disease evolution and against a background of uncertain/incomplete medical history, were discussed. The experts also considered the 2022 International League Against Epilepsy (ILAE) position paper for the definition of epilepsy syndromes in childhood, and its potential impact for directing the diagnosis of LGS. Keough and Thomas concluded by describing how raised awareness, vigilance, and support in diagnosis could help to optimise treatment and readjust the goals for the management of adults and children with LGS.

Possible Role of Dysbiosis of the Gut Microbiome in SLE.

The resident gut microbiota serves as a double-edged sword that aids the host in multiple ways to preserve a healthy equilibrium and serve as early companions and boosters for the gradual evolution of our immune defensive layers; nevertheless, the perturbation of the symbiotic resident intestinal communities has a profound impact on autoimmunity induction, particularly in systemic lupus erythematosus (SLE). Herein, we seek to critically evaluate the microbiome research in SLE with a focus on intestinal dysbiosis. SLE is a complex and heterogeneous disorder with self-attack due to loss of tolerance, and there is aberrant excessive immune system activation. There is mounting evidence suggesting that intestinal flora disturbances may accelerate the formation and progression of SLE, presumably through a variety of mechanisms, including intestinal barrier dysfunction and leaky gut, molecular mimicry, bystander activation, epitope spreading, gender bias, and biofilms. Gut microbiome plays a critical role in SLE pathogenesis, and additional studies are warranted to properly define the impact of gut microbiome in SLE, which can eventually lead to new and potentially safer management approaches for this debilitating disease.

Persistent and Quasipersistent Spin Textures in Halide Perovskites Induced by Uniaxial Stress.

Persistent spin textures are highly desirable for applications in spintronics, as they allow for long carrier spin lifetimes. However, they are also rare, as they require a delicate balance between spin-momentum coupling parameters. We used density functional theory simulations to predict the possibility of achieving these desirable spin textures through the application of uniaxial stress. Hybrid organic-inorganic perovskite MPSnBr3 (MP = CH3PH3) is a ferroelectric semiconductor which exhibits persistent spin textures near its conduction band minimum and mostly Rashba type spin textures in the vicinity of its valence band maximum. Application of uniaxial stress leads to the gradual evolution of the valence band spin textures from mostly Rashba type to quasipersistent ones under a tensile load and to pure Rashba or quasipersistent ones under a compressive load. The material exhibits flexibility, a rubber-like response, and both positive and negative piezoelectric constants. A combination of such properties may create opportunities for flexible and rubbery spintronic devices.

Opening a window to skin biomarkers for diabetes stage with optoacoustic mesoscopy

Being the largest and most accessible organ of the human body, the skin could offer a window to diabetes-related complications on the microvasculature. However, skin microvasculature is typically assessed by histological analysis, which is not suited for applications to large populations or longitudinal studies. We introduce ultra-wideband raster-scan optoacoustic mesoscopy (RSOM) for precise, non-invasive assessment of diabetes-related changes in the dermal microvasculature and skin micro-anatomy, resolved with unprecedented sensitivity and detail without the need for contrast agents. Providing unique imaging contrast, we explored a possible role for RSOM as an investigational tool in diabetes healthcare and offer the first comprehensive study investigating the relationship between different diabetes complications and microvascular features in vivo. We applied RSOM to scan the pretibial area of 95 participants with diabetes mellitus and 48 age-matched volunteers without diabetes, grouped according to disease complications, and extracted six label-free optoacoustic biomarkers of human skin, including dermal microvasculature density and epidermal parameters, based on a novel image-processing pipeline. We then correlated these biomarkers to disease severity and found statistically significant effects on microvasculature parameters as a function of diabetes complications. We discuss how label-free RSOM biomarkers can lead to a quantitative assessment of the systemic effects of diabetes and its complications, complementing the qualitative assessment allowed by current clinical metrics, possibly leading to a precise scoring system that captures the gradual evolution of the disease.

The effect of chemical variability and weathering on Raman spectra of enargite and fahlore

Abstract. Enargite (Cu3AsS4) and tennantite (Cu12As4S13) are typical As-bearing sulfides in intermediate- and high-sulfidation epithermal deposits. Trace and major element variations in enargite and tennantite and their substitution mechanisms are widely described. However, Raman spectra of the minerals with correlative quantitative chemical information are rarely documented, especially for enargite. Therefore, comparative electron and μ-Raman microprobe analyses were performed on enargite and fahlore grains. These spectra can be used in the industrial detection and subsequent removal of As-bearing sulfides prior to ore beneficiation in order to diminish the environmental impact of the metallurgical technologies. A simple Sb5+–As5+ substitution in enargite was confirmed by Raman analyses. Similarly, a complete solid solution series from tetrahedrite to tennantite (i.e., Sb3+–As3+ substitution) can be correlated with a gradual evolution in their Raman spectra. In turn, Te4+ occupies the As3+ and Sb3+ sites in fahlore by the coupled substitution Te4+ + Cu+ → (As, Sb)3+ + (Cu, Fe, Zn)2+. Accordingly, Raman bands of goldfieldite (Te-rich member) are strongly broadened compared with those of tetrahedrite and tennantite. A secondary phase with high porosity and a fibrous or wormlike texture was found in enargite in a weathered sample. The chemical composition, Raman spectrum, and X-ray diffraction signature of the secondary phase resemble tennantite. A gradual transformation of the primary enargite into this secondary phase was visualized by comparative electron and Raman microprobe mapping.

Elucidating the diffusion pathway of lithium ions in superionic halide solid electrolytes Li2+xHf1−xInxCl6 for all-solid-state lithium-metal based batteries

All-solid-state batteries (ASSBs) with inorganic solid-state-electrolytes (SSEs) have been regarded as the promising candidate for next-generation energy storage due to their high energy density and outstanding safety performance. However, the representative oxide and sulfide electrolytes suffer from low ionic conductivity and poor (electro)chemical stability, respectively. Herein, we report a series of new halide superionic conductors Li2+xHf1−xInxCl6 with high ionic conductivity up to 1.05 mS cm−1 at 30 °C that are simultaneously stable to high voltage. By means of the characterization techniques and bond-valence site energy (BVSE) calculation, insights into the effect of the phase transformation and underlying ionic transport mechanism by In substitution for Hf in Li2HfCl6 are provided. Importantly, with the increased amount of aliovalent substitution in Li2+xHf1−xInxCl6 microcrystal framework, a gradual structure evolution from trigonal to monoclinic phase has been observed, which is accompanied by the redistribution of Li-ions to generate two dimensionally (2D) preferable diffusion pathways through octahedral-tetrahedral-octahedral sites in In3+-substituted Li2HfCl6. Additionally, due to the oxidative stability of In-substituted Li2HfCl6, the bulk-type ASSBs with bare LiCoO2 deliver distinguished electrochemical performance.

Study on cross-scale temperature effect and damage failure evolution constitutive model of phthalazine ether sulfone ketone

Poly(phthalazine ether sulfone ketone) (PPESK) is a new type of thermoplastic resin materials with high temperature resistance and corrosion resistance. However, the failure evolution regularities of PPESK at different temperatures still remain poorly understood, which greatly limits the application of this composite. Therefore, quasi-static tensile/bending tests and microscanning microscopic characterization were used to study the multi-scale failure constitutive equation of PPESK. Based on cross-scale experimental observation methods, the spatial damage morphology of materials at different temperatures is explored, and the temperature boundary effect of PPESK is proposed to reveal the failure and failure mechanisms of materials in a wide temperature range. The initiation and evolution of pores at the micro scale of PPESK and the cumulative damage caused by craze propagation and cracking are essential factors of material failure, which also exhibit strong temperature sensitivity. The specific manifestation is the high-temperature viscous flow effect of the resin at the micro scale, as well as the gradual evolution trend of quasi-brittleness and viscoelastic-plasticity between the 295 K–472 K temperature range in the macro performance, which increases its plastic deformation ability by 1–5 times. Specifically, the mechanism of cross-scale micro-pore initiation and crack propagation was introduced, and a cross-scale, fully three-dimensional failure damage evolution constitutive model of PPESK was constructed for the first time in a wide temperature range. The secondary development of the material constitutive model in the finite element software was carried out, and the construction of the constitutive equation of the PPESK cross-scale failure was completed. Finally, the mapping relationship between the material's crack failure form, mechanical behavior, and the constitutive model was further verified by experiments. It is established that the proposed PPESK multi-scale failure constitutive model enables one to effectively describe the complex mechanical response and failure law of thermoplastic resin materials under temperature gradients. Moreover, this theoretical tool is promising for the design of independently controllable high-temperature resistant thermoplastic resin materials, thereby providing important guidance means for engineering applications.

The degradation of cathodic Fe/N/C catalyst in PEMFCs: The evolution of remanent active sites after demetallation

The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells (PEMFCs). However, the major bottleneck is its significant activity decay in real-world PEMFC cells. The superposed “fast decay” and “slow decay” have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation. The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test. Nevertheless, it is still unclear how the remanent active sites evolve after demetallation. To this end, the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies (MEAs) after different operations. It is presented that 1 bar pressure and 80 °C temperature are the optimized conditions for Fe/N/C MEA. Particularly, the “fast decay” in the initial 15 h is immune to the various operating parameters, while the “slow decay” highly depends on the applied temperature and pressure. According to the X-ray absorption spectra (XAS) analysis and stability test of MEA, the gradual evolution of Fe-N coordination to Fe-O is found correlated with the “slow decay” and accounts for the catalyst decay after the demetallation process.

Spatial mismatch and its evolution of new energy consumption, industrial structure upgrading, and carbon carrying capacity.

In view of the problems of insufficient exploitation of carbon emission reduction potential and low-carbon emission reduction efficiency caused by the spatial mismatch of economy, society, and ecological environment, this study used the ArcGIS10.8 intuitive expression tool, the barycenter model, and the spatial mismatch index to systematically investigate the spatial-temporal pattern and its spatial mismatch characteristics of new energy consumption, industrial structure upgrading, and carbon carrying capacity in 30 provinces in China from 2009 to 2019. The findings of this study included mainly the following aspects. (1) The new energy consumption level showed the significant differences in spatial aggregation. The industrial structure upgrading level decreased from the southeast to the northwest. The carbon carrying state showed the gradual geographical evolution characteristics of the empty load, suitable basic load, suitable load, and overload from the southeast to the northwest. (2) The barycenter of new energy consumption shifted from the south to the north; the barycenter of industrial structure upgrading presented a phased migration trajectory of first to the northwest, then to the south, and then to the southwest; the barycenter of carbon carrying capacity oscillated from the southwest to the northeast. (3) Provinces with the positive mismatch of new energy consumption, industrial structure upgrading, and carbon carrying capacity were widely distributed, but provinces with the negative mismatch were sporadically distributed. The spatial mismatch degree of the three elements tended to expand on the whole, but the direction and magnitude of change were different. The high mismatch areas showed a trend of agglomeration in eastern coastal economic circles such as the Bohai Rim, the Yangtze River Delta, and the Pearl River Delta. Moreover, the high mismatch areas showed a trend of westward spread. (4) The contribution of province to the overall spatial mismatch decreased from the eastern to the western. This study would provide a reference for the related research on carbon peaking, carbon neutrality, and the coordinated high-quality development between economy-society and ecological environment.

Talkin' Bout a Revolution? Institutional Change in the EU Recovery and Resilience Facility: The Case of Climate Policy

AbstractThe European Union (EU) post‐COVID‐19 investment and reform programme, the Recovery and Resilience Facility (RRF), has been hailed as novel and ambitious, both as a fiscal instrument and as a lever for accelerating progress towards EU climate commitments. Yet, its design also exhibits strong path dependency, drawing on existing processes and commitments. Adapting theories of institutional change and models of hard/soft governance, we argue that the RRF is an example of significant yet gradual change – of evolution rather than revolution – taking place via layering and conversion of existing frameworks, and alteration of their logics of action. We show how the RRF repurposes the European Semester and track continuity and change in climate policy, a key priority area. Our findings suggest that the literature on institutional change should give greater consideration to the interplay between layering and conversion as a mechanism of gradual yet transformative evolution.

The Activities of Local Development Investment Funds in several Countries and Lessons Learned for Vietnam

This paper presents a comprehensive set of recommendations tailored for Vietnam's approach to Development Investment Funds (DIFs) by drawing insights from the experiences of China, India, Colombia, Tunisia, Thailand, and Malaysia. The study underscores the need for a flexible approach to DIF models, highlighting the gradual evolution of models in well-established markets that are customized to specific development conditions and legal systems. This adaptability fosters competition, accommodates diverse investment products, and aligns with the dynamic financial market trends shaped by liberalization and globalization. Overall, this paper provides a comprehensive roadmap for Vietnam to strategically implement and manage DIFs, drawing upon a rich tapestry of international experiences to ensure effective, adaptive, and successful DIF operations in the local context.a

The trade-sustainability nexus: the evolution of the European Commission’s trade and sustainable development discourse from 1993 to 2022

ABSTRACT This paper provides an in-depth analysis of the European Commission’s trade and sustainable development discourse from 1993 to 2022. By employing a discursive institutionalist framework and examining a comprehensive corpus of over 1,400 press documents, this study traces the discursive process that has created both significant changes to, and persistent elements in, the Commission’s trade-sustainability agenda. The analysis reveals noteworthy shifts within the discourse, notably a transition from a primary concern with labour and human rights during the 1990s to an increased focus on economic development and poverty reduction in the early 2000s. This was followed by a discernible move towards more stringent differentiation among developing countries and an amplified emphasis on reciprocity. In recent years, we are witnessing a strong focus on environmental and climate protection, labour rights, and enforceability. The findings underscore the enduring presence of trade-sustainability ideas within EU trade policy and their gradual evolution over time, while contributing to the literature on the role of ideas in shaping the Union’s external policies.

Historical insights into the evolution of local self-government and state administration

This article aims to provide historical insights into the evolution of local self-government and state administration. The purpose of this study is to explore the development and transformations of these governance systems over time. The research methodology employed involves an extensive review of historical literature, archival records, and case studies to analyze the evolution of local self-government and state administration. The findings of this study reveal the gradual emergence and evolution of local self-government structures, highlighting the complex interplay between local communities and central authorities. The historical analysis demonstrates how these governance systems have adapted to social, political, and economic changes throughout history. The practical implications of this research lie in a deeper understanding of the historical context and dynamics that have shaped contemporary local self-government and state administration. This knowledge can inform policymakers and government officials in designing effective and responsive governance structures that align with the needs and aspirations of local communities. By shedding light on the historical development of local self-government and state administration, this article contributes to a broader understanding of the governance systems that underpin contemporary societies. It underscores the importance of historical insights in shaping future governance models and policies for a more inclusive and participatory approach to governance.

Optimized Strain Response in (Co0.5Nb0.5)4+-Doped 76Bi0.5Na0.5TiO3-24SrTiO3 Relaxors

High strain with low hysteresis is crucial for commercial applications in high precision actuators. However, the clear conflict between the high strain and low hysteresis in BNT-based ceramics has long been an obstacle to actual precise actuating or positioning applications. To obtain piezoceramics with high strain and low hysteresis, it is necessary to enhance the electrostrictive effect and develop an ergodic relaxor (ER) and nonergodic relaxor (NR) phase boundary under ambient conditions. In this work, (Co0.5Nb0.5)4+ doped 76Bi0.5Na0.5TiO3-24SrTiO3 (BNST24) relaxors were fabricated using the conventional solid state reaction route. X-ray diffraction patterns revealed the B-site substitution in BNST24 ceramics. By adjusting the (Co0.5Nb0.5)4+ doping in BNST24, we effectively tuned the TNR-ER and Td close to ambient temperature, which contributed to the development of the ergodic relaxor phase and enhanced the electrostrictive effect at ambient temperature. The I-P-E loops and bipolar strain curves verified the gradual evolution from NR to ER states, while the enhanced electrostrictive effect was verified by the nearly linear S-P2 curves and improved electrostrictive coefficient of the BNST24-xCN relaxors. An enhanced strain of 0.34% (d*33 = 483 pm/V) with low hysteresis of 8.9% was simultaneously achieved in the BNST24-0.02CN relaxors. The enhanced strain was mainly attributed to the proximity effect at the ER and NR phase boundary of BNST24-0.02CN, while the improved electrostrictive effect contributed to the reduced strain hysteresis. Our work demonstrates an effective strategy for balancing the paradox of high strain and low hysteresis in piezoceramics.