High recorded color rendering performance of single-structured Ce,Mn:Y_(3)(Al,Sc)_(2)Al_(3)O_(12)phosphor ceramics for high-power white LEDs/LDs

Achieving a high color rendering index(CRI)and luminous stability in single-structured Ce:Y_(3)Al_(5)O_(12)(Ce:YAG)phosphor ceramics(PCs)is crucial for high-power white light-emitting diodes or laser diodes(LEDs/LDs).However,cyan valleys and insufficient amounts of the red component in the Ce:YAG emission spectra significantly limit their real applications.In this work,a series of Ce,Mn:Y_(3)(Al,Sc)_(2)Al_(3)O_(12)(Ce,Mn:YSAG)PCs were fabricated by vacuum sintering,and efficient spectral regulation was realized for full-color lighting.The cyan valley was filled by the blueshifted emission peak of Ce^(3+)via Sc^(3+)doping.The orange‒red emission at approximately 580 nm was effectively supplemented via Mn^(2+)doping.In particular,CRI of Ce,Mn:YSAG increased from 56.4 to 85.8,a 52%increase compared with that of Ce:YAG under high-power LED excitation,and the operating temperature was stable at approximately 50℃for long working time.Moreover,CRI of 80.9 could still be obtained for PC-based white LDs.These results indicated that Ce,Mn:YSAG PC,which has excellent CRI and luminous stability,is an extremely promising color convertor for high-power white LEDs/LDs.

Evolution of domain structure in 0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O_(3)0.04(Bi_(0.50)Na_(0.50))ZrO_(3) ceramics with poling and temperature

Domain structure often has significant influences on both piezoelectric properties and piezoelectric temperature stability of a ferroelectric ceramic.In-depth studies on the characters of domain structure should be helpful for the better understanding of piezoelectric performance.In this work,the evolution of domain structure in large-d_(33)0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O_(3)-0.04(Bi_(0.50)Na_(0.50))ZrO_(3) ceramics with poling and temperature was systematically investigated via comparing the various domain patterns that are obtained by acid-etching.It was found that domain structure changes greatly upon poling and varies largely with temperature.Complex domain patterns consisting of long narrow parallel stripes or herringbone structure separated by 180°domain boundaries are observed in the unpoled ceramics at room temperature.Domain patterns become less complicated upon poling,due to the collective polarization reversals of parallel-stripe domain clusters and banded fine-stripe domain segments.Parallel stripes and herringbone bands become much wider upon poling,as some narrow stripes and herringbone bands coalesce into broad ones,respectively.Hierarchical domain structure is commonly seen in the domain patterns acid-etched at room temperature,but is less frequently recognized at elevated temperatures.Schematic models of domain configurations were proposed to explain the domain structure and its evolution with poling.