Ceramics

The photoluminescence (PL) and photoluminescence excitation (PLE) spectra of an EFG-grown (−201) β-Ga₂O₃ single crystal were recorded at 7 and 300 K at the FinEstBeAMS beamline of the MAX IV Laboratory. Excitation–emission maps and fixed-wavelength PLE profiles covered 4.50–10.50 eV at both temperatures. Each temperature series was normalized to its own 5.00 eV intensity and, alternatively, to its own maximum; the reported ratios therefore describe excitation dependence within one series and not an absolute difference in luminescence yield between temperatures. At 7 K, integrated emission at 10.50 eV retains 95.4% of its 5.00 eV value and 89.2% of its maximum. At 300 K, the PLE half-height is 4.55 eV, and the maximum occurs at 4.75–4.80 eV, followed by a decrease to 2.26% of the 5.00 eV value and 2.03% of the maximum at 10.50 eV. Room-temperature ellipsometry on the same factory-polished face places the PLE rise in the rapidly increasing absorption region and yields a penetration depth of approximately 0.24 μm near the PLE half-height and 37 nm at 5.90 eV. A constrained depth-dependent calculation does not reproduce the full decline, so surface capture is retained as one possible pathway rather than an established mechanism. The emission is described by the same effective bands at 3.55, 3.37 and 3.07 eV used in the preceding laser study. Their balance is nearly constant at 7 K, whereas the low-energy spectral weight increases at 300 K under deep-VUV excitation. These spectra provide quantitative reference profiles for energy conversion and carrier capture in β-Ga₂O₃.

Phosphate glasses with the compositions 60P₂O₅–15ZnO–15CaO–10Li₂O (PZCL) and 60P₂O₅–15ZnO–15CaO–10V₂O₅ (PZCV) (mol%, expressed as oxides) were synthesized by the melt-quenching method. The prepared glasses were characterized by using X-ray powder diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). X-ray diffraction shows only broad diffuse halos without Bragg reflections, indicating that both glasses are X-ray amorphous. Raman analysis confirms that PZCL behaves as a typical alkali-modified ultraphosphate glass containing Q³ and Q² units, whereas PZCV contains characteristic V–O vibrational modes indicating that vanadate groups are integrated into the phosphate backbone. SEM observations reveal smooth surfaces at low magnification for both glasses; at higher magnification, PZCV shows a compact and homogeneous surface with fine, uniformly dispersed granules, whereas PZCL displays a more textured surface with agglomerates and plate-like features. EIS analysis using the Havriliak–Negami model reveals that the free-charge carrier contribution appears as a step in M′(ω,T) and a peak in M″(ω,T), allowing a clear distinction between conductivity relaxation and interfacial polarization or dipolar effects, with conductivity derived from the M″(ω,T) peak frequency. PZCV shows dc conductivity approximately one order of magnitude higher than PZCL (1.5 × 10⁻⁹ vs. 1.8 × 10⁻¹⁰ S·cm⁻¹ at 120 °C). The temperature dependence follows Arrhenius behavior, with activation energies of about 0.89 eV for PZCV and 1.04 eV for PZCL. The electrode polarization observed at low frequencies with ion-blocking gold electrodes indicates a significant ionic contribution in both glasses, although a polaronic (V⁴⁺/V⁵⁺) contribution to the conductivity of PZCV cannot be excluded. Capacitance analysis reveals a slight increase with temperature for both samples, with PZCV consistently showing higher values (~7 pF) than PZCL (~5 pF). Although the absolute conductivities remain far below those required for practical solid electrolytes, these results clarify how the replacement of Li₂O by V₂O₅ modifies charge transport and dielectric relaxation in P₂O₅-rich Zn–Ca phosphate glasses.

Multiphasic calcium phosphate (CaP) composites made of hydroxyapatite (HAp), α-tricalcium phosphate (α-TCP), or β-tricalcium phosphate (β-TCP) are promising for biomedical applications. In this paper, the changes in Raman spectra of a series of HAp/α-TCP and HAp/β-TCP were calibrated and new algorithms using microRaman spectroscopy were established for an efficient and quantitative analysis of the constituent phases in multiphasic CaP systems, taking advantages of their characteristic Raman bands. The reliability of the proposed Raman algorithms was further examined and verified by the investigation of a tri-phase CaP mixture and thermally treated monolithic ceramics of HAp, α-TCP and β-TCP using both Raman and XRD analyses. The results demonstrated the applicability of the proposed method for quantitative phase evaluation, as well as higher sensitivity of Raman spectroscopy to nonstoichiometric alteration for more precise phase control and quality evaluation in the presence of defects in multiphasic CaP systems.