Pr Ceramics Research Articles

Large electric field-induced strain and excellent photoluminescence properties of Pr-modified 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 lead-free ferroelectric ceramics

The 0.94Bi0.5-xPrxNa0.5TiO3-0.06BaTiO3 (BNT-6BT-xPr) lead-free ceramics with doping content of x = 0, 0.01, 0.025, 0.04, 0.05, 0.075, and 0.1 were synthesized by the conventional solid-state reaction method. After doping with the Pr element, a composition-induced phase transition took place, which from the rhombohedral perovskite (R3c) and tetragonal perovskite (P4bm) phases coexisting into the pseudo-cubic phase. At the same time, the introduction of the Pr element had a beneficial effect on grain growth, and the average size of the crystal particle increased from 299 to 742 nm. The Curie temperature Tm showed no obvious change with the increasing Pr content, but the temperature TF-R of the ferroelectric-relaxor phase transition was gradually shifted toward lower temperatures. In addition, the depolarization temperature Td gradually decreased from 125 to 53 °C. In the BNT-6BT-0.025Pr ceramics, giant electric field-induced strain (Smax) and normalized piezoelectric coefficient (d33*) were obtained (Smax = 0.58%, d33* = 723 pm/V). Furthermore, a significant photoluminescence emission intensity was achieved, exhibiting a bright red color. Due to significant enhancement of the piezoelectric and the photoluminescence properties, the BNT-6BT-0.025Pr ceramics exhibited strong competitiveness in actuators and multifunctional devices, which may broaden their application fields.

Defect elimination to enhance photoluminescence and optical transparency of Pr-doped ceramics for self-calibrated temperature feedback windows

Pr-doped metal oxide polycrystalline transparent ceramics are highly desirable for photothermal window systems served in extreme environments, however, obtaining efficient photoluminescence together with high transparency in these ceramics is still posing serious challenges, which undoubtedly limits their applications. Here, Pr-doped Y₂Zr₂O₇ (YZO) transparent ceramics, as an illustrative example, are prepared by a solid-state reaction and vacuum sintering method. Owing to the elimination of defect clusters [ Pr_Y⁴⁺-O^2- - Pr_Y⁴⁺] and [Pr_Y⁴⁺ - e'] without introduction of impurities and additional defects, the fabricated YZO:Pr ceramics exhibit high transparency (74 %) and efficient photoluminescence (39-fold enhanced) after air annealing plus vacuum re-annealing treatment. Moreover, upon 295/450 nm excitation, the emission bands (blue, green, red, and dark red) from YZO:Pr ceramic present different temperature-dependent properties due to the thermal quenching channel generated by the intervalence charge transfer state (IVCT) between Pr³⁺ and Zr⁴⁺ ions. Furthermore, a self-calibrated temperature feedback window with same FIR model (I₆₁₃/I₅₀₃) under different excitation light sources (295 nm and 450 nm) is designed. The developed photothermal window operated in a wide temperature range (303 - 663 K) shows relatively high sensitivities (<em>S</em>_a and <em>S</em>_r reach 0.008 K^-1 at 663 K and 0.47 % K^-1 at 363 K, respectively), high repeatability (&gt; 98 %), and low temperature uncertainty (&lt; 3 K). This work presents a paradigm for achieving enhanced photoluminescence along with elevated transparency of lanthanides doped ceramics through vacuum re-annealing treatment engineering and demonstrates their promising potential for photothermal window systems.

Simultaneous coloration erasure and significant photoluminescence enhancement via vacuum re-annealing in lanthanide-doped transparent ceramics

A simple and efficient route for the coloration erasure and significant photoluminescence enhancement of lanthanide-doped transparent ceramics was novelly developed in this work. As for the illustrative examples, full-band high transparency and efficient luminescence of YZO:Tb and YZO:Pr ceramics were received after air annealing plus vacuum re-annealing processes. The defect clusters [LnY4+-O2−-LnY4+] and [LnY4+-e′] were also proposed for the relevant reaction mechanisms involving air annealing and vacuum re-annealing processes. Insight in the vacuum re-annealing strategy might open up a path towards controllably tailoring the optical transmission and transition properties of lanthanide-doped highly transparent ceramics.

Effects of sintering temperature on the microstructure and luminescence of LuAG:Pr ceramics

The effects of the sintering temperature on the microsctruture and luminescence of Lu3Al5O12:Pr (LuAG:Pr) ceramics was investigated by density, X-ray diffraction (XRD), scanning electron microscopy (SEM), grain size, attenuated total reflection Fourier transform infrared spectroscopy (ATR FTIR), photoluminescence (PL), radioluminescence (RL), and thermoluminescence (TL) measurements. A Czochralski-grown single crystal was used as reference. The increase of the sintering temperature promoted progressive structural modifications toward the characteristics of the single crystal. The presence of an amorphous phase was strongly detrimental to the luminescence of LuAG:Pr, with its elimination leading to enhanced RL and reduced TL emission. Evidence of synergism between the F-related defects and the Pr3+4f - 4f and 4f - 5d transitions was also found with the presence of these defects being detrimental to the 5d - 4f scintillation.

Scintillation properties and effect of thermal annealing in Lu3Al5O12:Ce and Lu3Al5O12:Pr ceramics

The impact of thermal annealing on the properties of LuAG:Ce and LuAG:Pr ceramics has been investigated. The results of measurements of pulse height spectra, scintillation time profiles, absorption spectra, radioluminescence as a function of temperature, absorption spectra, as well as low temperature thermally stimulated luminescence, performed before and after annealing of the samples in air, are compared. Pulse height spectra are used to estimate the light outputs of the samples, while scintillation time profiles to find the decay time constants. Absorption spectra are analyzed to identify the observed lines and/or bands. Radioluminescence spectra examine the changes of particular emissions as a function of temperature. Finally, parameters of traps detected in thermally stimulated luminescence are determined by decompositions of the recorded glow curves.

Fabrication, optical and scintillation properties of (Lu0.75,Y0.25)AG:Pr ceramic scintillators

Y3+ admixing Lu3Al5O12:Pr ceramics are fabricated successfully by the solid state reaction method and further optimized by an air-annealing process. Optical absorption, photoluminescence spectra and scintillation properties such as radioluminescence, and light output are measured and compared with those of the Y3+ free LuAG:Pr ceramics. Positive effect of Y3+ codopant consists mainly in the significant increase of scintillation light output, as well as the decrease of relative intensity of slow component. With 0.15% Pr3+ codoping, the obtained LuYAG:Pr ceramic displays a light output of 28500 ph/MeV at 3 μs shaping time, higher than that of the LuAG:Pr ceramic scintillators ever report. The effect of Y3+ admixture is further explained by vacuum ultraviolet and electron spin resonance experiment.

Synthesis and luminescence properties of BaHfO3: Pr ceramics

BaHfO3 sintered ceramic scintillators doped with various Pr concentrations (0–1mol%) were synthesized at 1700°C in N2–H2 atmosphere. XRD, SEM and photo-luminescent techniques at various temperatures (40K to 550K) were employed to reveal properties of the BaHfO3:Pr ceramics. Results of spectroscopic investigation indicate that the luminescence is connected almost exclusively with decay of the 3P0 level, while the emission from 1D2 is hardly seen even for higher Pr3+ concentrations. However, the intrinsic emission of BaHfO3 matrix, related with defects or impurities, seems to compete with the emission of Pr3+ ions. The 3P0 luminescence decays give time constant of about 25–32μs in the 40–550K range of temperatures, while the 1D2 decay time depends on the dopant concentration and gets shorter above 300K for 1% specimen due to a cross relaxation process between Pr3+ ions.

Gd2O2S: Pr Scintillation Ceramics from Powder Synthesized by a Novel Carbothermal Reduction Method

Gd2O2S: Pr ceramics were fabricated by spark plasma sintering using the powders synthesized by carbothermal reduction method. The calcination temperature, carbon content, and other preparation conditions of the powders are optimized. The results indicate that the carbon content in the raw mixture has a great influence on the final phases of the phosphor powders. A possible reaction process and mechanism are also proposed. The spectroscopic properties of Gd2O2S: Pr phosphors and ceramics are studied by the photoluminescence (PL) and X‐ray excitation luminescence (XEL) spectra, in which show a green emission at 513 nm was detected as the main emission under the UV and X‐ray excitation.

The photoluminescence and electrical properties of lead-free (Bi0.5Na0.5)TiO3:Pr ceramics

Pr doped lead-free (Bi0.5Na0.5)TiO3(BNT) ceramics were fabricated using the solid-state reaction method. The dependences of photoluminescence properties on process conditions, dopant concentration, and charge compensation were systematically investigated. The results showed that Pr-doped BNT ceramics exhibited strong red emitting properties with a single peak centered at 610nm upon blue light excitation (440–505nm), while maintaining high piezoelectric properties. The emission intensities reached the optimal value as the holding time is 2h at 1150°C for BNT:0.003Pr sample. Especially, the red emission intensity of BNT:xPr3+ can be more effectively enhanced by introducing the (Bi0.5Na0.5)2+ vacancies as the charge compensation due to the formation of trapping centers, than the alkali metal ions (Li+, Na+, K+) as compensators. In addition to the intrinsic piezoelectric properties, the excitation band of BNT:xPr material can well realize the compatibility with existing blue light-emitting diode chips (450–470nm), compared to the ultraviolet or infrared light excitation luminescent materials, indicating that this system may have significant technological promise in novel multifunctional devices.

Effect of B on Light Output Uniformity of Gd&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;S: Pr Ceramics Scintillator

High uniformity of light output is required for scintillators utilized in detectors for high resolution X-ray CT. It was found that the uniformity of light output of Gd2O2S: Pr ceramics scintillator decreased with nonuniformity in B content in the sintered body. The B content depends on the particle size; raw material powders with smaller particle size contain higher B content. It was thought that the nonuniformity in B content in the sintered body was caused by the difference in the content of the fractions of smaller particles at each part of the compaction body.

Effect of Ce on Radiation Damage of Gd&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;S: Pr Ceramics Scintillator

For improvement of the image quality of X-ray CT, X-ray detector requires more sensitive and low afterglow scintillator. In order to realize the requirements, Gd2O2S: Pr ceramics scintillator which has a light output of 1.8 times of CdWO4 is now in practical use. Ce doped in the Gd2O2S: Pr ceramics scintillator is effective for reducing undesirable afterglow. The effect of Ce on the radiation damage was studied in this paper. The radiation damage decreased with increase in Ce content. It was considered that Ce reduced the color centers and traps.