---
title: "Sm and Ni Co-doping Modulates Optical and Electrical Properties of PMN-PT Ceramics"
id: "plos-one-21-effect-of-sm-and-ni-co-doping-on-optical-and-electrical-properties-of-lead"
canonical_url: "https://medichelpline.com/clinical-feed/plos-one-21-effect-of-sm-and-ni-co-doping-on-optical-and-electrical-properties-of-lead"
content_type: "clinical_feed_article"
specialty: "General"
source_name: "PLOS ONE (Medicine)"
source_url: "https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0357271"
published_at: "2026-09-01T14:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Sm and Ni Co-doping Modulates Optical and Electrical Properties of PMN-PT Ceramics
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/plos-one-21-effect-of-sm-and-ni-co-doping-on-optical-and-electrical-properties-of-lead
- **Specialty:** [General](https://medichelpline.com/clinical-feed/general.md)
- **Primary Source:** PLOS ONE (Medicine)
- **Source URL:** [Original Journal Publication](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0357271)
- **Published At:** 2026-09-01T14:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- This study experimentally investigates **Sm** (samarium) and **Ni** (nickel) co-doping in Pb(Mg1/3Nb2/3)O3-PbTiO3 (**PMN-PT**) ceramics to explore structure–property relationships, with emphasis on optical and electrical behavior. - Motivation: Ni2+ doping previously reduced bandgaps in alkaline niobates via Ni2+–oxygen-vacancy defect dipoles; the role of Ni2+ in PMN-PT had not been studied. - Sm3+ is used as an A-site co-dopant (analogous to Ba2+ in prior work) to help maintain charge balance and alter tolerance factor in the perovskite lattice while preserving piezoelectric performance. - Six specimen families were prepared by solid-state synthesis with controlled stoichiometries; processing included ball milling, calcination, binder-assisted pressing, sintering (1200–1250 °C) and some samples were N2-annealed at 1000 °C to generate pyrochlore phases. - Sample sets included A (71PMN-29PT with 2.5 mol% Sm), with A_per (air-sintered perovskite dominant) and A_pyr (N2-annealed, pyrochlore dominant). B and C families included an additional 5 mol% Ni introduced by different routes to distinguish Ni-VO defect formation from stoichiometric PNN-PT solid-solution formation. - Characterization covered phase identification, microstructure, optical absorption, photoconductivity, charge trapping, phase transitions, and piezoelectric energy-harvesting performance. - Key findings: Ni2+ behaves differently in PMN-PT than in alkaline niobates, but **Sm/Ni co-doping** can tune phase transitions, **photoconductivity**, charge carrier trapping, and optical absorption while retaining reasonable piezoelectric energy-harvesting properties. - The work provides experimental insight into the role of Ni2+ in the band structure of Sm‑PMN‑PT perovskite and pyrochlore phases and supplies openly available data at a FAIR repository.
## Clinical Analysis & Structured Key Points
Effect of Sm and Ni co-doping on optical and electrical properties of lead magnesate niobate titanate ceramics | PLOS One Browse Subject Areas ? Click through the PLOS taxonomy to find articles in your field. For more information about PLOS Subject Areas, click here . Article Authors Metrics Comments Media Coverage Peer Review Reader Comments Figures Figures Abstract The ability to manipulate the bandgap while maintaining strong ferroelectricity in perovskite oxides offers numerous functional advantages, including multimodal energy harvesting/sensing, current modulation, dual-source actuation, electric-free poling, and enhanced bulk photovoltaic effect. However, bandgap engineering of Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT) – renowned for its outstanding piezoelectric properties – via Ni 2+ doping remains unexplored, despite its prior success in alkaline niobates. This study provides a comprehensive characterization of the structure-property relationships in Sm/Ni co-doped PMN-PT ceramics, especially for their optoelectrical properties. The results show that Ni 2+ doping behaves differently than in alkaline niobates. Nevertheless, Sm/Ni co-doping effectively tunes the phase transition, photoconductivity, charge carrier trapping, and optical absorption while retaining reasonable piezoelectric energy harvesting performance. Overall, this work offers insights into the role of Ni 2+ in the band structure of Sm-PMN-PT perovskite and pyrochlore phases. Citation: Aias D, Balanov V, Khansur NH, Pankratova V, Anandakrishnan SS, Yadav S, et al. (2026) Effect of Sm and Ni co-doping on optical and electrical properties of lead magnesate niobate titanate ceramics. PLoS One 21(9): e0357271. https://doi.org/10.1371/journal.pone.0357271 Editor: Talaat Abdel Hamid, National Research Centre, EGYPT Received: May 31, 2026; Accepted: August 14, 2026; Published: September 1, 2026 Copyright: © 2026 Aias et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The data that support the findings of this study are openly available in Fairdata.fi Etsin at DOI: https://doi.org/10.23729/0d53169f-65df-4ec7-9c17-b96266fcad75 , reference number 23. Funding: (1) Funded by the European Union (ERC, UNIFY, 101039110). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them; (2) Co-funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 101002219); (3) Co-funded by the Israel Science Foundation, grant number 1479/21; (4) Acknowledgement is also extended to the MAX IV Laboratory for the experimental time on the FinEstBeAMS under Proposal No. 20220653. Research conducted at the MAX IV, a Swedish national user facility, is supported by the Swedish Research Council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and the Formas under contract 2019-02496. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Introduction In the early 2010s, Ni 2+ doping was proposed as a strategy to engineer the bandgaps of polar oxide perovskites with the ABO 3 structure [ 1 , 2 ]. In these materials, the optical bandgap is typically defined by transitions between O 2p states forming the valance band maximum (VBM) and B-site transition metal d states forming the conduction band minimum (CBM). The strong electronegativity difference in these B-O bonds produces large spontaneous polarization, making many ABO 3 perovskites, including PbTiO 3 , BaTiO 3 , and KNbO 3 , excellent ferroelectric, piezoelectric, and pyroelectric materials for sensors, actuators, transducers, and energy harvesters. However, the same bonding characteristics generally result in wide bandgaps exceeding 3 eV, limiting visible-light absorption. Lower bandgaps have mainly been reported in the BiMeO 3 family, where compounds such as BiFeO 3 , Bi(Fe 0.5 Cr 0.5 )O 3 , and BiMnO 3 achieve bandgaps of approximately 2.7 eV, 1.4 eV, and 1.2 eV, respectively, while retaining useful ferroelectricity when the appropriate crystal structures are maintained [ 3 – 5 ]. Grinberg et al. predicted by density functional theory (DFT) that substituting Nb 5+ with Ni 2+ and simultaneously creating oxygen vacancies could reduce the KNbO 3 bandgap from over 3.5 eV to about 1.1 eV through the formation of Ni 2+ -oxygen-vacancy defect dipoles [ 1 ]. Subsequent experimental studies by Bai et al. confirmed this mechanism in KNbO 3 and (K,Na)NbO 3 systems, achieving improved visible-light absorption accompanied by increased photoconductivity while maintaining remanent polarizations of 3−15 µC cm -2 [ 6 – 8 ]. In these compositions, Ba 2+ was co-doped on the A-site to compensate for the changes in tolerance factor and charge balance introduced by Ni 2+ doping. Similar approaches have been explored in other perovskite oxides [ 9 – 11 ]. Bandgap-engineered ferroelectrics offer opportunities for applications leveraging the optical modulation or multimodal coupling of electrical properties [ 12 – 14 ]. Despite this potential, the optical and electrical behavior of Ni 2+ -doped ABO 3 perovskites remains insufficiently understood. Notably, the role of Ni 2+ in photoferroelectric properties has not yet been explored in Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT), one of the most technologically important piezoelectric systems. In this study, Ni 2+ is introduced to the B-site of PMN-PT ceramics together with Sm 3+ co-doping on the A-site. Here, Sm 3+ is analogous to the role of Ba 2+ in alkaline niobates introduced above. PMN-PT was selected because compositions near the morphotropic phase boundary exhibit outstanding piezoelectric properties, making them attractive candidates for future photoresponsive piezoelectric devices and multi-source energy harvesters [ 15 , 16 ]. Sm 3+ doping has also been reported to enhance the piezoelectric performance [ 17 , 18 ]. Because the Sm/Ni co-doped PMN-PT system is too compositionally complex for practical DFT treatment, particularly given the strong correlated Ni 3d and Sm 4f electrons, experimental investigation provides the most feasible route for understanding its behavior. This work therefore presents a comprehensive study of the structure, microstructure, and optical/electrical properties of Sm/Ni co-doped PMN-PT ceramics. Materials and methods Sample preparation Ceramic samples were produced using the solid-state method, starting with reactants of PbO (99.9%, Sigma-Aldrich, USA; 99.9%, Thermo Scientific, USA), MgO (≥ 99%, Sigma-Aldrich, USA), Nb 2 O 5 (99.9%, Sigma-Aldrich, USA; 99.9%, Alfa Aesar, USA), TiO 2 (99.9% Sigma-Aldrich, USA; 99.8%, Alfa Aesar, USA), Sm 2 O 3 (99.9%, Aldrich, USA), and NiO (99.999%, Aldrich Chemistry, USA). The reactants were accurately weighed according to the stoichiometries, and the mixtures were ball milled at 150 rpm for 6 h in a 500 ml ZrO 2 jar with ethanol and 3 mm ZrO 2 beads. The ceramic slurries were dried in an oven at 80–120 °C overnight. Calcination was carried out in a muffle furnace at 860 °C for 4 h, with the mixed reactants placed in an Al 2 O 3 crucible. The calcined powder was ball-milled at 150 rpm for 12 h. A 5 wt% binder (5 w/v% polyvinyl alcohol dissolved in deionized water) was employed to facilitate the shaping of green bodies from the calcined powders. Green body pellets, each with a diameter of 10 mm, were uniaxially pressed under a pressure of approximately 40 MPa. The green bodies were then fired at 550 °C for 4 h with a heating rate of 2 °C per minute to eliminate the binder, followed by sintering at 1200–1250 °C for 4 h in a muffle furnace. Powder beds of identical compositions were utilized to prevent Pb loss during the high-temperature treatment. After sintering, some samples were annealed in an N 2 atmosphere at 1000 °C for 2 h. For this study, a total of six types of specimens were prepared, as outlined in Table 1 . As indicated in Table 1 , the A sample family was designed to be a 71PMN-29PT, doped with 2.5 mol% Sm on the A-site. After sintering at 1250 °C in the air for 4 h, a predominant perovskite phase, referred to as A_per, was formed. By further annealing A_per in a N 2 atmosphere at 1000 °C for 2 h, a pyrochlore phase was formed, which replaced the original perovskite phase as the major phase, and was designated as A_pyr. The B and C sample families were designed with an additional 5 mol% Ni doping into the A samples. Download: PNG larger image TIFF original image Table 1. Summary of specimens in this work. https://doi.org/10.1371/journal.pone.0357271.t001 However, it is important to note that Pb(Ni 1/3 Nb 2/3 )O 3 -PbTiO 3 (PNN-PT) is also a commonly researched, stable solid solution which can form PNN-PMN-PT solid solutions in conjunction with PMN-PT [ 19 ]. To differentiate the intention of creating Ni 2+ -oxygen-vacancy defect dipoles (Ni-V O ) from the stoichiometric PNN-PT solid solution, the 5 mol% Ni dopant was introduced in distinct ways. In the B family, the 5 mol% Ni was designed to occupy the Mg-sites by correspondingly reducing the MgO concentration in the mixture of the starting reactants, thereby creating a Mg-deficient off-stoichiometry. In the C family, the 5 mol% Ni was designed to occupy the Nb-sites by correspondingly reducing the Nb 2 O 5 in the mixture of the starting reactants, thereby creating a Nb-deficient off-stoichiometry. As a result, the B family emulated the PMN-PNN-PT ternary solid solution with a minor stoichiometric PNN component, serving as the control specimen, while the C family aimed to create Ni-V O , serving as the experimental specimen. In a manner similar to the A family, the B and C samples were sintered at 1200 °C in air for 4 h, resulting in the formation of major perovskite phases, referred to as B_per and C_per in Table 1 , respectively. Corresponding pyrochlore phases, namely B_pyr and C_pyr, emerged as the major phases after further annealing the B_per and C_per samples under the same conditions that were applied to the A_per samples. Characterization The calcination temperatures were determined using DSC/TGA (differential scanning calorimetry/thermogravimetric analysis, STA449 F3, Netzsch, Germany). The structures of the sintered and annealed ceramic samples were identified using XRD (X-ray diffraction, Bruker D8 Advance eco, equipped with a Cu source and a position selective detector, Germany). Diffraction data were collected in the reflection geometry between the 2θ range of 15−80 ° with a step size of 0.02 ° and acquisition time of one second at each step. Rietveld refinement was carried out using the SmartLab Studio II software and the PDF-5+ for accessing the ICDD database. The samples, after being sintered and annealed, were polished using silicon carbide abrasive papers with grit sizes ranging from P1200 to P2500. This was followed by further polishing on a plate with a suspension that had a particle size of 1 µm (Struers, France). The surfaces of the polished samples were examined under a field-emission scanning electron microscope (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDX) (ULTRA plus, Zeiss, Germany). Additionally, the samples were examined using electron-probe microanalysis (EPMA, JXA-8530F Plus, JEOL, Japan) and X-ray photoelectron spectroscopy (XPS, ESCALAB 250Xi, Thermo Fisher Scientific, USA) for identification of composition and stoichiometry. The optical properties were initially characterized using UV-vis-NIR spectrophotometry (Cary 500 Scan, Varian, USA). The thickness of all the measured samples was controlled to be approximately 200 µm to ensure comparability among the collected data. The spectrophotometry was followed by luminescence spectroscopy, which was performed under synchrotron radiation excitation at 10 K in the photoluminescence (PL) end station FINESTLUMI of the FinEstBeAMS undulator beamline at the MAX IV synchrotron facility (Sweden) [ 20 – 22 ]. The excitation energy range was between 4.5 and 7.5 eV, and the excitation spectra were normalized using a calibration curve obtained with the AXUV-100G diode. Luminescence detection in the visible spectral range (520–800 nm) was carried out using the Andor Shamrock (SR-303i) 0.3 m spectrometer, with a grating of 300 l mm -1 and a blaze of 500 nm. The spectrometer was equipped with a CCD camera (Newton DU970P-BVF, Oxford Instruments, UK) that covers the 300–1100 nm spectral range. Prior to electrical characterizations, the sample surface was coated with a silver paste (735825, Sigma-Aldrich, South Korea) and cured at 150 °C. The dielectric and ferroelectric properties at room temperature (RT) were measured using an LCR meter (E4980AL, Keysight, USA) and a ferroelectric evaluation system (RT6000HVA, Radiant Technologies, USA), respectively. The piezoelectric properties at RT were characterized by a Berlincourt meter (YE2730A, APC International, USA) and an impedance analyzer (E4990A, Keysight, USA). The temperature-dependent dielectric parameters and I-V (current-voltage) curves were obtained using another LCR meter (4284A, Hewlett Packard, USA) and a source meter (2450, Keithley, USA), respectively. A sample stage equipped with coaxial probes (THMS 600) and its corresponding controlling unit (TMS 94/LNP, Linkam, UK) were used to control the measurement temperature. Monochromatic lasers (OBIS LX/LS series, Coherent, USA) with wavelengths of 405 nm, 552 nm, and 660 nm at a nominal power of 20 mW served as the light source for the I-V curve measurement. For I-V curve measurements at RT, a triaxial probe station (PVX400, Wentworth Laboratories, UK) was employed for more precise signal processing. For the I-V curve measurement, it is important to note that an in-plane electrode configuration was established by depositing a pair of Au electrodes on the sample surface, maintaining a gap of approximately 150 µm. This configuration is depicted in S1 Fig . Results and discussion All original datasets and their corresponding analyses related to this work are openly accessible [ 23 ]. Phases, microstructure, and compositions of perovskites Fig 1a presents the results of the XRD analysis. The Rietveld refinement results are shown in S2 Fig ., which confirmed a reasonably good fitting between the measured and calculated patterns. The refinement/instrument parameters, peak lists and other detailed refinement data can be found in the associated datasets [ 23 ]. S3 – S9 Figs . depict the FESEM/EDX and EPMA images in which the perovskite and pyrochlore phases can be located. According to the XRD patterns, predominant tetragonal perovskite phases have been identified in the A_per, B_per, and C_per samples, which yielded more than 95% relative density ( Table 1 ). The pristine A_per sample and the Ni-doped B_per sample also exhibited minor pyrochlore phases, a common occurrence in Pb-based perovskite oxides. The existence of pyrochlore phases in the A_per and B_per samples was further corroborated by the EDX and EPMA maps ( S3 – S4 and S9 Figs .). Although the Rietveld refinement also suggested a minor pyrochlore phase in the C_per sample, this phase was not discernible in either the EDX or EPMA maps ( S5 and S9 Figs ). This suggests that the pyrochlore phase could be disregarded in the C_per sample. Download: PNG larger image TIFF original image Fig 1. XRD and XPS results. (a) XRD patterns of the samples made in this work and the clay used to hold the samples in place during measurement; XPS results of (b) Ni 2p and (c) O 1s for the samples. https://doi.org/10.1371/journal.pone.0357271.g001 Upon examining the EPMA results ( Table 1 ), it is evident that the B_per and C_per samples indeed generated distinct off-stoichiometries among Mg, Ni, and Nb. The B_per sample produced a Mg/Nb ratio of 1/2.9, whereas this ratio for the C_per sample stood at 1/2.5. By adjusting the ratios through the integration of the Ni concentration into the Mg-site, the nominal (Mg + Ni)/Nb ratios were established at 1/2.2 and 1/2.0 for the B_per and C_per samples, respectively. When compared to the original Mg/Nb ratio of 1/2.3 for the A_per sample, these calculations confirm the success of the Ni-doping in terms of the intended variation of stoichiometry. Fig 1b shows the XPS results of Ni 2p for all the samples, which confirm the Ni 2+ state as designed [ 24 ]. Fig 1c shows the XPS results of O 1s, where the C_per sample exhibited signs of an additional oxygen local environment that is much less prominent in A_per and B_per (see the shoulder between 531–532 eV). Because C_per was designed to reduce Nb 5+ whilst introducing Ni 2+ , the strong charge imbalance tends to create oxygen vacancies, which we believe is responsible for the additional oxygen state in C_per. In comparison, A_per was designed to be fully oxidized and in B_per the replacement of Mg 2+ with Ni 2+ did not cause charge imbalance, and hence they show identical oxygen states. This suggests that the designed contrast of Ni-V O between C_per and A_per/B_per is successfully realized. The distinct doping strategies also induced a significant alteration in the phase transition behavior. Fig 2 illustrates the temperature-dependent dielectric properties of the perovskite samples. The pristine A_per sample exhibited a T C of approximately 100 °C, while the T C of the B_per sample declined to nearly 65 °C. The C_per sample exhibited a T C of about 85 °C. Notably, the tetragonal-cubic phase transition (around T C ) in the C_per sample appeared to be considerably broader than those in the A_per and B_per samples – full width at half maximum of 100–110 °C for A_per and B_per whereas 160 °C for C_per. Download: PNG larger image TIFF original image Fig 2. Dielectric properties. Dependence of relative permittivity ( ε r ) and dielectric loss (tan δ ) on temperature measured at 10 kHz and 100 kHz under the dark condition for the A_per, B_per and C_per samples. https://doi.org/10.1371/journal.pone.0357271.g002 The variation of T C could be the outcome of the varying Mg/Ni/Nb ratios as discussed earlier. Grain size could also influence the T C or phase transition behavior [ 25 ]. However, the grain sizes of the A_per, B_per and C_per samples are deemed to be similar where the negligible difference is not expected to induce as obvious changes for T C and phase transition as those shown in Fig 2 . The phase transition behavior is more likely to be altered due to the changed chemical pressure or defect concentration caused by the varying Mg/Ni/Nb ratios among the A_per, B_per and C_per samples. Phases, microstructure, and compositions of pyrochlores As pyrochlore phases were not eliminated, to assist identifying possible influence of the secondary phase on the material properties, all the perovskite samples were annealed in N 2 . This process transformed all the perovskite samples into full pyrochlore phases. As depicted in Fig 1a , the samples A_pyr, B_pyr, and C_pyr exhibited dominant pyrochlore phases (space group Fd -3 m :2). The precise compositions of these phases were calculated based on the EPMA results ( Table 1 ). The FESEM images, along with the EDX and EPMA maps, revealed a significantly porous microstructure and showed no evidence of the retained perovskite phase ( S6 – S9 Figs ). The XPS results suggest the Ni 2+ state in A_pyr, B_pyr and C_pyr are identical to the state before annealing. An additional oxygen local environment, which is more prominent in A_pyr and C_
## Related Clinical Research

- [Reinforced-count simulation: calibrating decisions under over-dispersed multi-type service demand](https://medichelpline.com/clinical-feed/plos-one-3-reinforced-count-simulation-for-decision-calibration-under-over-dispersed-multi.md)
- [Psychometric validation of the Patient-Centered Communication Scale (PCCS) in Iranian clinical nur](https://medichelpline.com/clinical-feed/plos-one-7-psychometric-features-of-the-patient-centered-communication-scale-among-iranian.md)
- [Torpor-Induced Reversible Immune Suppression in Thirteen-Lined Ground Squirrels: Mechanisms and Ce](https://medichelpline.com/clinical-feed/biorxiv-1-mechanistic-investigation-of-reversible-hibernation-driven-immune-suppression.md)
- [Rapid standardized soil-based protocol for seedling drought tolerance screening in small grain cer](https://medichelpline.com/clinical-feed/biorxiv-6-standardized-and-rapid-protocol-for-drought-tolerance-screening-at-seedling.md)
- [Reduce Gun Access to Prevent Suicide: Evidence and Policy Options](https://medichelpline.com/clinical-feed/kff-health-news-0-it-s-hard-to-predict-who-will-be-suicidal-it-s-easier-to-ensure-people-can-t.md)

## Navigation
- [← Back to General Feed](https://medichelpline.com/clinical-feed/general.md)
- [← All Clinical Specialties](https://medichelpline.com/clinical-feed.md)
## Medical & Regulatory Disclaimer

> [!CAUTION]
> MedicHelpline content is structured for research, educational, and professional discovery purposes. It does not constitute individual medical advice, clinical diagnosis, or treatment recommendations.
> Always verify dosing, contraindications, and regulatory alerts against official product labeling and primary regulatory sources before clinical decision-making.