Solid-State Synthesis: Controlling Phase, Defect and Dopant · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Firing solids on purpose

Science · Chemistry · ages 22-23
Name ______________________   Date ____________

  1. What is an interstitial defect?

    • A missing atom at its site
    • A foreign atom on a normal site
    • An extra atom squeezed between regular sites

  2. Which solid conducts electricity and can be bent?

    • A metallic solid with a shared electron sea
    • An ionic solid of paired opposites
    • A molecular solid of weakly gripped molecules

  3. Small defect populations can change a solid's color, strength, and conductivity.

    Circle one:   True   False

  4. You must raise an oxide's conductivity. Which dopant plan fits?

    • A same-valent swap that changes nothing to balance
    • Firing colder with no dopant at all
    • A lower-valent cation on a higher-valent site, balanced by holes or vacancies

  5. Firing in low-oxygen air adds oxygen vacancies to an oxide. What shifts with them?

    • Only the mass of the sample
    • Carriers and color along with the vacancy count
    • Nothing, since vacancies are invisible

  6. The powder pattern shows stray peaks beside the target lines. What happened?

    • The wanted phase formed perfectly
    • A rival phase won part of the firing
    • The detector needs recalibrating before any reading

  7. A student sees perfect powder lines and declares the defect population ideal. What is wrong?

    • Powder lines confirm the phase, not the defect count
    • Powder lines can never confirm any phase
    • Defects always destroy the whole pattern

  8. To favor your holes from a lower-valent dopant, how should you set the firing air?

    • Fix the air first, since oxygen pressure also moves vacancies and carriers
    • Ignore the air, since only the dopant sets carriers
    • Pump in extra oxygen, since more oxygen always means more holes
LightMySky · lightmysky.comW1-mt_5gri5iZ0lV-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

Firing solids on purpose W1-mt_5gri5iZ0lV-s1

  1. An extra atom squeezed between regular sites · Vacancy is missing, substitution is swapped, interstitial is squeezed between.
  2. A metallic solid with a shared electron sea · The electron sea carries current and lets layers slide.
  3. True · Placement mistakes are small in count and large in effect.
  4. A lower-valent cation on a higher-valent site, balanced by holes or vacancies · The imbalance must be balanced, and the balancing carriers raise conductivity.
  5. Carriers and color along with the vacancy count · The air grows or heals vacancies, and carriers follow.
  6. A rival phase won part of the firing · Extra peaks are extra phases, not sharper proof of the target.
  7. Powder lines confirm the phase, not the defect count · Phase proof and defect proof are different claims needing different checks.
  8. Fix the air first, since oxygen pressure also moves vacancies and carriers · Dopant and air share the same carrier balance, so both controls must agree.
Worksheet · LightMySky