皮皮学，免费搜题
登录
搜题
【简答题】
( 书 p.105 第 四 题 ) 固体发光材料是一种能将激发的能量转变为可见光的固体物质。在基质中掺入杂质,质量分数可达千分之几或百分之几,可调整发光效率、余辉及发光光谱。如在刚玉 Al 2 O 3 基质中掺入 0.05~1.0% 的 Cr 3 + 及在 Y 2 O 3 基质中掺入 Eu 3 + 等均可制成固体发光材料。 ( a) 推测 Al 2 O 3 基质中掺入 Cr 3 + 的发光原理。 ( b) Y 2 O 3 属立方晶系,将 Y 2 O 3 的立方晶胞分为 8 个小立方体, Y 在小立方体的面心和顶点, O 位于小立方体内的四面体空隙,画出 4 个这样的小立方体,指出 Y 和 O 的配位数。
拍照语音搜题，微信中搜索"皮皮学"使用
参考答案：
参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【简答题】A boy, about 10 years old, got to my clinic with his sick cat for cure. Thc cat was a tiny beautiful thing, about the boy's own 36 . I could see she was 37 very strong and lovely with the fur of a 38 ...
【简答题】A man has got an old cat and a young cat. He likes them very much. A friend comes to see him and finds two holes(洞) in his door. One is big, the other is small. “My dear friend”, he says, “why are the...
【单选题】What is the functions of the sealants that are used on the flight compartment windows？
A.
prevent moisture penetration
B.
prevent water entrapment
C.
provide aerodynamic flushness of the outer window pane and the window frame
D.
All of the above
【简答题】like the cat that got/ate/swallowed the canary (US) like the cat that ate the canary like a cat that's got the cream
【单选题】关于 SELECT 语句,下面说法错误的是( )
A.
SELECT语句可以查询表或视图中的数据
B.
SELECT语句只能从一个表中获取数据
C.
在SELECT语句中可以设置查询条件
D.
在SELECT语句中可以对查询结果进行排序
【单选题】When demand is relatively inelastic, a 5% increase in price will:
A.
increase total revenue by more than 5%.
B.
increase total revenue by less than 5%.
C.
decrease total revenue by more than 5%.
D.
decrease total revenue by more than 5%.
相关题目：