Red-emitting piezoluminescence (elasticoluminescence) is achieved by doping rare earth Pr into the well-known piezoelectric matrix, LiNbO . By precisely tuning the Li/Nb ratio in nonstoichiometric Li NbO :Pr , a material that exhibits an unusually high piezoluminescence intensity, which far exceeds that of any well-known piezoelectric material, is produced. Li NbO :Pr shows excellent strain sensitivity at the lowest strain level, with no threshold for stress sensing. These multipiezo properties of sensitive piezoluminescence in a piezoelectric matrix are ideal for microstress sensing, damage diagnosis, electro-mechano-optical energy conversion, and multifunctional control in optoelectronics.

Fedotovite K_{2}Cu_{3}O(SO_{4})_{3} is a candidate of new quantum spin systems, in which the edge-shared tetrahedral (EST) spin clusters consisting of Cu^{2+} are connected by weak intercluster couplings forming a one-dimensional array. Comprehensive experimental studies by magnetic susceptibility, magnetization, heat capacity, and inelastic neutron scattering measurements reveal the presence of an effective S=1 Haldane state below T≅4  K. Rigorous theoretical studies provide an insight into the magnetic state of K_{2}Cu_{3}O(SO_{4})_{3}: an EST cluster makes a triplet in the ground state and a one-dimensional chain of the EST induces a cluster-based Haldane state. We predict that the cluster-based Haldane state emerges whenever the number of tetrahedra in the EST is even.

Observation of a quantum spin liquid (QSL) state is one of the most important goals in condensed-matter physics, as well as the development of new spintronic devices that support next-generation industries. The QSL in two dimensional quantum spin systems is expected to be due to geometrical magnetic frustration, and thus a kagome-based lattice is the most probable playground for QSL. Here, we report the first experimental results of the QSL state on a square-kagome quantum antiferromagnet, KCu 6 AlBiO 4 (SO 4) 5 Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation (μSR), and inelastic neutron scattering (INS) measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state.

We discovered a new near-infrared (NIR) persistent luminescent material Sr2SnO4:Nd3+, which exhibited NIR luminescence ranging from 850 to 1400 nm. Furthermore, we successfully enhanced the intensity of NIR persistent luminescence by increasing the firing temperature. The intensity of NIR persistent luminescence, which penetrates through a human finger and can be used to visualize a finger vein pattern by using a charge-coupled device camera, reached approximately 1.1 mW/m2 (λ = 900 nm) at a decay time of 10 s after ceasing the excitation. We proposed the enhancement process of the NIR persistent luminescence for Sr2SnO4:Nd3+ in conjunction with photoluminescence, absorption, thermoluminescence, and structural properties.

No abstract