A good LED phosphor must possess strong enough absorption, high quantum yields, colour purity, and quenching temperatures. Our synthesized Y2Mo4O15:Eu3+ phosphors possess all of these properties. Excitation of these materials with near-UV or blue radiation yields bright red emission and the colour coordinates are relatively stable upon temperature increase. Furthermore, samples doped with 50% Eu3+ showed quantum yields up to 85%, what is suitable for commercial application. Temperature dependent emission spectra revealed that heavily Eu3+ doped phosphors possess stable emission up to 400 K and lose half of the efficiency only at 515 K. In addition, ceramic disks of Y2Mo4O15:75%Eu3+ phosphor with thickness of 0.71 and 0.98 mm were prepared and it turned out that they efficiently convert radiation of 375 and 400 nm LEDs to the red light, whereas combination with 455 nm LED yields purple colour.

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The difficulty of beta tricalcium phosphate (β-TCP) crystallization in aqueous media opens the question whether β-TCP can be produced using an alternative pathway. Amorphous calcium phosphate (ACP) is metastable in an aqueous environment and prefers a more stable apatite phase. Others have transformed a crystallized calcium deficient hydroxyapatite (Ca-def HAp) into β-TCP, but automatic transformation from ACP to Ca-def HAp followed by transformation to β-TCP has not been addressed. This work shows the formation of Ca-def HAp after different aging times of ACP and the subsequent transition to β-TCP. An amorphous phase with a Ca/P ratio of 1.5 was synthesized, rinsed, filtered and excess fluid removed for maturation. The resulting apatite was monitored with X-ray diffraction at different temperatures. Heating at 700 °C then investigated the transition to β-TCP. It was found that Ca-def HAp formed at short aging times produced a combination of alpha and beta phases, but a longer aging time led to pure β-TCP.

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In this study, nanostructured Ce- and Sm-substituted Ca10(PO4)6(OH)2 samples have been synthesized using an aqueous sol-gel chemistry route. For the characterization of obtained specimens, the XRD, SEM, UV-visible reflection and IR spectroscopy and luminescence measurements were recorded. It was shown that phase purity of the end products highly depends on the amount of lanthanide element. The reflectance of lanthanide-substituted calcium hydroxyapatite samples is wavelength independent in the wavelength range of 450-800 nm and equal almost 100%. The cerium-substituted samples show a significant decrease of transmission at ~300 nm. The characteristic samarium absorption line (~430 nm) is evident in the UV-vis reflection spectra of samarium-substituted hydroxyapatites.