Effects of Bi nonstoichiometry on (Bi0.5+xNa)TiO3 (BNT) ceramics were investigated at x=−1–+2 mol % of Bi0.5 covering Bi deficiency and excess. At all compositions, rhombohedrally symmetric BNT perovskite formed without secondary phases. Increasing x caused smaller grains. Higher piezoelectric coefficient (d33) but lower depolarization temperature (Td) occurred at Bi excess than at Bi deficiency and vice versa. Leakage current at room temperature decreased with decreasing x. Electrical conductivity of the stoichiometric BNT (x=0) from 700 to 900 °C increased with decreasing partial oxygen pressure from 1 to 10−5 atm suggesting n-type conductivity at elevated temperatures.

Background:The main objective of this study was to conduct a meta-analysis to identify the effects of reminiscence therapy in people with dementia (PWD).Methods:A systematic search of randomized controlled trials (RCTs) was conducted using bibliographic databases. A total of 157 original published studies were identified in the search, and 24 complete articles were included in the final review to check for the level of evidence. Two of the study authors independently assessed the quality of the included studies using the “Risk of Bias” (ROB) tool developed by the Cochrane Collaboration. Depression, quality of life, and behavioral and psychological symptoms of dementia (BPSD) were selected to measure the effect of reminiscence therapy. To determine the effects of reminiscence therapy on these variables, each individual study was analyzed using Comprehensive Meta-Analysis Software® (Biostat, Englewood, NJ, USA).Results:The overall effect size was presented using standardized mean differences (SMDs) and 95% confidence intervals. Cohen’s d effect size for depression was −0.541 (95% CI: −0.847 to −0.234, Z = −3.730, p<0.001), indicating that depression was significantly reduced in the reminiscence group compared to the control group. Increased quality of life and decreased BPSD were also found in the reminiscence group compared to the control group.Conclusion:Reminiscence therapy has a moderate effect on depression and can be broadly used to decrease depression as an alternative to antipsychotics, which can have harmful side effects and high cost.

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Effects of Na nonstoichiometry in (Bi0.5Na0.5+x)TiO3 ceramics were investigated in the range of x=(−5)−(+1) mol % of Na0.5. A rhombohedral perovskite structure was maintained at all compositions with no secondary phases. Grain size decreased with Na nonstoichiometry. Piezoelectric coefficient (d33) increased from 74 pC/N at x=0 up to 91 pC/N at x=−3.5 then dropped with further Na deficiency. Depolarization temperature (Td), on the other hand, decreased from 190 °C at x=0 down to 112 °C at x=−3.5 then increased. Rhombohedral lattice distortion (90−α) decreasing with Na deficiency was a key factor for the variation in d33 and Td.

Lead‐free piezoelectric ceramics, 0.96[{Bi0.5 (Na0.84K0.16)0.5}1−xLix(Ti1−yNby)O3]–0.04SrTiO3 (BNKLiTN–ST) with x, y = 0–0.030, were synthesized by solid‐state reaction method. X‐ray diffraction patterns indicated that Li and Nb successfully diffused into the BNKT–ST lattice and formed a pure perovskite structure with x, y ≤ 0.025. Increasing the Li and Nb contents (x, y = 0.020) induced a phase transformation from the coexistent rhombohedral–tetragonal phases for pure BNKT–ST ceramics to a pseudocubic phase, resulting in degradation of the remnant polarization and coercive field. However, the field‐induced strain was markedly enhanced at x, y = 0.020, giving rise to a giant dynamic piezoelectric constant (d33* = Smax/Emax = 800 pm/V). Furthermore, the temperature dependence of the field‐induced strain response showed temperature‐insensitivity up to 120°C. To explore its potential for device applications, a 10‐layered stack‐type multilayer actuator was fabricated from the optimal composition (x, y = 0.020). This actuator showed a large Smax/Emax of 600 pm/V at a relatively low driving field of 4.5 kV/mm suggesting highly promising results in lead‐free BNT‐based ceramics.