The unprecedented borate hydride Sr5(BO3)3H and deuteride Sr5(11BO3)3D crystallizing in an apatite‐related structure are reported. Despite the presence of hydride anions, the compound decomposes only slowly in air. Doped with Eu2+, it shows broad‐band orange‐red emission under violet excitation owing to the 4f65d–4f7 transition of Eu2+. The observed 1H NMR chemical shift is in good agreement with previously reported 1H chemical shifts of ionic metal hydrides as well as with quantum chemical calculations and very different from 1H chemical shifts usually found for hydroxide ions in similar materials. FTIR and Raman spectroscopy of different samples containing 1H, 2H, natB, and 11B combined with calculations unambiguously prove the absence of hydroxide ions and the sole incorporation of hydride ions into the borate. The orange‐red emission obtained by doping with Eu2+ shows that the new compound class might be a promising host material for optical applications.

Lead-free piezoelectric ceramics with nominal composition at morphotropic phase boundary Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZ) prepared by different processing routes and sintered either by conventional solid-state reaction or by spark plasma sintering (SPS) techniques were comparatively investigated to observe the role of structural modifications and of microstructures on the dielectric, ferroelectric, piezoelectric and electrocaloric responses. The ceramics presented relative densities from 75% to 97% and showed variations in their phase composition as a result of variable mixing and different synthesis and sintering parameters providing local compositional heterogeneity. As result, all of the ceramics showed diffuse phase transition and ferroelectric switching responses, with parameters affected mostly by density (Pr between 3.6 to 10.1 μC/cm2). High values for the electrocaloric response in the Curie range were found for the ceramics with predominantly orthorhombic character. Field-induced structural modifications were probed by tunability anomalies and by XRD experiments in remanence conditions. Piezoelectric effects with notably high figure of merit values were assigned to the better densification and poling efficiency of BCTZ ceramics.