Two-step Precursor Method Research Articles

Effect of Pr3+ doping on relaxation behavior and strain response of PHT-based piezoelectric ceramics

Heterovalent ion doping has influenced the further development of piezoelectric applications. Pr3+ doping in relaxor ferroelectrics is rarely focused on piezoelectric performance enhancement. 0.51 Pb(Ni1/3Nb2/3)O3-0.49 Pb(Hf0.3Ti0.7)O3 (PNN-49PHT) ceramics with Pr3+ doping ceramics were designed and fabricated by a two-step precursor method. Excellent dielectric diffusion coefficient (γ) of 1.96 was achieved at the low Pr3+ doping concentration of 0.2 %. Increased relaxation enhanced the nanoscale domains formation, resulting in a giant strain response (d*33) of 1400 pm/V at 10 kV/cm, and a total strain (Stol) of 0.27 % at 20 kV/cm. Structural refinement unveiled that the high piezoelectricity originated from the mainly substitution of Pr3+ for Pb2+ at the A-site, inducing lattice distortion and phase transitions. Local domain switching and long-range ordered destruction were investigated by piezoresponse force microscopy (PFM) and Scanning Electron Microscopy (SEM). These findings contribute to the advancement of piezoelectric devices and provide valuable insights for the design and optimization of high-performance piezoelectric ceramics.

Synthesis of possible room temperature superconductor LK-99: Pb9Cu(PO4)6O

The quest for room temperature superconductors has been teasing scientists and physicists, since its inception in 1911 itself. Several assertions have already been made about room temperature superconductivity, but have never been verified or reproduced across the labs. The cuprates were the earliest high transition temperature (T c) superconductors, and it seems that copper has done the magic once again. In July 2023, a Korean group synthesized a lead apatite based compound LK-99, showing a T c of above 400 K (Lee et al 2023 arXiv: 2307.12008; 2023 arXiv: 2307.12037; Lee et al 2023 J. Korean Cryst. Growth Cryst. 33 61). The signatures of superconductivity in the compound are very promising, in terms of resistivity (ρ = 0) and diamagnetism at T c. Although, the heat capacity (C p) did not show the obvious transition at T c. Inspired by the interesting claims of the above room temperature superconductivity in LK-99, in this article, we report the synthesis of polycrystalline samples of LK-99, by following the same heat treatment as reported in Lee et al (2023 arXiv: 2307.12008; 2023 arXiv: 2307.12037) using a two-step precursor method. The phase is confirmed through x-ray diffraction measurements, performed after each heat treatment. The room temperature diamagnetism is not evidenced by the levitation of a permanent magnet over the sample or vice versa. The isothermal magnetization measurement at 280 K shows that as synthesized sample of LK-99 is paramagnetic. Further measurements for the confirmation of bulk superconductivity in variously synthesized samples are underway. Our results on the present LK-99 sample, synthesized at 925 °C, as of now do not confirm the appearance of bulk superconductivity at room temperature. Further studies with different heat treatments are underway.

Piezoelectric and pyroelectric properties of Mn-doped 0.36Pb(In1/2Nb1/2)O3–0.36Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 ceramics

0.5 mol% Mn-doped 0.36Pb(In1/2Nb1/2)O3–0.36Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 (Mn-PIMNT) ceramics were fabricated by a two-step precursor method. The phase structure, morphologies, and temperature-dependent dielectric, ferroelectric, piezoelectric, and pyroelectric properties were studied. The results indicated that the Mn-PIMNT ceramics had pure perovskite phase and uniform grain distribution. Meanwhile, it exhibited ultrahigh piezoelectric coefficient d33 of 235 pC/N, high-power figure of merit (FOM) of 60,160 pC/N, large remnant polarization Pr of 34.57 µC cm−2 and coercive field EC of 12.97 kV cm−1, which were much better than that of binary Mn-PMNT ceramics. Moreover, by Mn ions-doping, giant pyroelectric coefficient p up to 4.8 × 10–4 C m−2 K−1 was obtained and the figure of merits for the detectivity Fd reached 2.317 × 10–5 Pa−1/2, higher than PIMNT ceramics. Combined with the outstanding piezoelectric and pyroelectric properties as well as high ferroelectric rhombohedral to tetragonal phase transition temperature Trt (up to 146 ℃) and ferroelectric tetragonal to cubic phase transition TC of 188 ℃, it is suggested that the Mn-PIMNT ceramics are an excellent candidate for piezoelectric and pyroelectric devices.